CA2015509C - Method and apparatus for controlling a blower motor in an air handling system - Google Patents
Method and apparatus for controlling a blower motor in an air handling systemInfo
- Publication number
- CA2015509C CA2015509C CA002015509A CA2015509A CA2015509C CA 2015509 C CA2015509 C CA 2015509C CA 002015509 A CA002015509 A CA 002015509A CA 2015509 A CA2015509 A CA 2015509A CA 2015509 C CA2015509 C CA 2015509C
- Authority
- CA
- Canada
- Prior art keywords
- motor
- signal
- speed
- air flow
- torque
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D7/00—Control of flow
- G05D7/06—Control of flow characterised by the use of electric means
- G05D7/0617—Control of flow characterised by the use of electric means specially adapted for fluid materials
- G05D7/0629—Control of flow characterised by the use of electric means specially adapted for fluid materials characterised by the type of regulator means
- G05D7/0676—Control of flow characterised by the use of electric means specially adapted for fluid materials characterised by the type of regulator means by action on flow sources
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D27/00—Control, e.g. regulation, of pumps, pumping installations or pumping systems specially adapted for elastic fluids
- F04D27/004—Control, e.g. regulation, of pumps, pumping installations or pumping systems specially adapted for elastic fluids by varying driving speed
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B30/00—Energy efficient heating, ventilation or air conditioning [HVAC]
- Y02B30/70—Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S236/00—Automatic temperature and humidity regulation
- Y10S236/09—Fan control
Abstract
Apparatus and method for controlling a a motor having a stationary assembly with a plurality of winding stages for carrying motor current and further having a rotatable assembly in driving relation with a blower in an air handling system. The apparatus provides control of the blower speed over a range of static pressure variations to maintain relatively constant preselected rate of air flow in the system. The apparatus receives a preselected flow rate signal representing the preselected air flow rate. A
microprocessor, responsive to both the preselected flow rate signal and a speed signal, generates a desired torque signal which is a function of both the preselected flow rate signal and the speed signal. The desired torque signal is compared to a signal representing motor torque and a comparison signal representing the comparison is generated. An IC control applies a motor voltage to one or more of the winding stages at a time in accordance with the comparison signal and commutatss the winding stages in a preselected sequence to rotate the rotatable assembly. As a result, the blower is driven by varying the motor torque according to motor speed to maintain substantially constant air flow in the system at the preselected rate substantially independent of variations in the static pressure.
microprocessor, responsive to both the preselected flow rate signal and a speed signal, generates a desired torque signal which is a function of both the preselected flow rate signal and the speed signal. The desired torque signal is compared to a signal representing motor torque and a comparison signal representing the comparison is generated. An IC control applies a motor voltage to one or more of the winding stages at a time in accordance with the comparison signal and commutatss the winding stages in a preselected sequence to rotate the rotatable assembly. As a result, the blower is driven by varying the motor torque according to motor speed to maintain substantially constant air flow in the system at the preselected rate substantially independent of variations in the static pressure.
Description
l9bjw ~ 0~ 5 5 ~ 9 03-Lo-6262 GEN 9225 PATE~T
METHOD AND APPARATUS FOR CONTROLLING
A B~.OW~ MQTOR IN A~ AIR ~A~DI.ING SYST~
Fiel~ o~ the I~ve~tio~
This invention relates in general to systems for condltioning the temperature of a space and, in particular, to a Rystem ~or conditionlng air and for maintaining a pre-selected flow rate of the conditioned air through at least a part of ths system regardless of the static pressure therein, a method of operating a system for conditioning air, and a circuit.
Back~ro-ln~ of the InvRntio~
In th~ past, va~ious dif~erent techniques are bRliev~d to have been utilizsd in an attempt to flow air through a contained space of a system including an apparatus for conditioning the temperature of the air with the rate of such air flow being.related to the static pressure associated with ~uch system. Both th~ speed and torque of an electric motor driving a fan or blower to effect air flow through the system are affected by the static pressure in the system.
The rate of air flow ~CFM - cubic ~eet per minute) through the apparatus also a~fects the motor spasd and torque.
One approach of the past in~olved the rather laborious and time consuming matching of motor speed and torgue with th~ proper fan to appro~imate the desired air ~ 25 flow rat~ for the particular contai~ed spac~ and static ; pre~ure o~ the particular apparatus or system in which such apparatu~ was employ2d. However, this did not accommodate variation~ in the~static pressure in the system caused by alterations in the system such as ope~ing, closing or adjust-ing of a v~nt or the like connecting a conditioned space in air flow relation with the system~
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l9bjw 03-LO-6262 . . GE~ 9~25 201~0~ PATENT
If the fan or hlower utilized in the past was of the fan or blade typ~, a decrease in the static pr~ssure acting on such fan re~ulted in an increase in th~ speed of t~e Fan and tha elec~ric motor driving it. Conversely, if the static prcssure acting on the fan was increased, the speed of th~ fan and electric motor decreased. Thus, the speed of the fans a~d electric motors utilized in the past varied inversely with a variation of the static pressure in the system.
As recogni~ed in coassigned U.S. patent No.
4,806,833, incorporated herain by reference in its entirety, a d~crease in th~ statie pressure acting on a squirrel cage blower results in 2 decrease in the sp~ed of the squirrel eage blower and the electric motor driving it. Conversely, 15 if the ~tatic pressu~e acting on the squirrel cage blower is increased, the speed of the squirrel cage blower and its driving el~ctric motor is increased. Thus, it was found that the speed o~ th~ squirrel eage blower and its dri~ing elec-tric motor varies directly with a variation in the static pressure. Accordingly, U.S. patent No. 4,806,~33 discloses a : method of operating a system for conditioning air including a variable speed hlower ~or flowing the conditio~ed air through a contain~d space having a static pressure therein. In this : sys~em, the ~~~ed of the blower is set to a~fect a prese-lected flow rate at an e~isting st~tic pressure in th~ con-tained space and the sp~ed of the blower is altered only in respon~ to a variation in the static pressure and only i~
follo~ing relation with the static pressure variation. The spe~d alteration of the blower is sensed, and the speed of th~ blower is altered in following relation with the sensed speed alteration to establi~h the preselected flow rate through the contained space at the vari~d static pressure acting on the blower.
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, lsbiw 2 01~ 5 09 03-Lo-6262 GEN 9225 PATENr Although this approach is an improvement over the prior art, it is only a rough appro~imation o~ the charac~er-istics needed to achieve constant air flow with respect to changes in static pressure. In general, the systems of the prior art worked reasonably well over a limited range of air ~10ws and static pressures by employing a singl~ slope speed comp~nsation techniqu~. It has now been re~ognized that a much more accu.rate approach to providing sp~ed compensated torgue which can he implemented in an air handli.ng system is required. Such speed compensated torque would then allow the blow~r motor to maintain air flow in the system ind~pendent o~ variations in the static pressure in the duct work.
~mm~rY of the I~nkio~
~mong the several objects of the present invention may be noted the provision of an improved system for condi-tioning air and for maintaining a preselected air ~low rate of the conditioned air through at least a part of the system regardle~s o~ the static pressure therein, an improved method of opera~ing the system, and an improved circuit which will o~ercome the ahove-discussed disadvantages or undesirable features as well as others, of the prior art; the provision of such improved sy~tem and method in which the preselected flow rate is accurately controlled; the provision of such improved system and method in which wide variations in the ; 25 static pressure are readily accommodated; the pro~ision of such improved system and method in which the torque of a a dynamoelectric ~achine driving blower means is altered with variations in the speed of the motor to maintain constant air flow rat~ independent of static pressure on the blower means;
~0 the provision of such improved system and method in which the energi2ation of a dynamoelectric machine is adjustably regu-lated in order to maintain the preselected flow rate at static l9bjw 03~LO-6262 GEN 9225 2 015 5 0 9 PATE~T
pressure variations acting on the blower maans; and the pro-vision of such improved system, method and circuit u~ilizing a microprocessor and oth~r component parts which are simple in design, easily assembled and economically manu~actured.
The~s as well as other ohjects and advantageous features of the pr~sent invention will be in part apparent and in part pointed out hereinafter.
In general, an apparatus is provided in one form of the invention for controlling a dynamoelectric machine such as a ~otor having a stationary assembly with a plurality of winding stages for carrying motor current and further having a~rotatable assembly in driving relation with a blower in an air handling syst2m. The apparatus provides control of the blower torque over a range o~ static pressure variations to lS maintain relatively constant preselected rate of air f low in th~ system. Th~ apparatus is adapted to receive a preselected flow rate Rignal represent~ng the preselected air flow rate.
Means provides a mo~or torque signal representative of the motor torque. Means provides a speed signal representative 20 of thè speed of the motor. A microprocessor which is respon-sive to both the preselected flow rate signal and t~e ~peed signal generates a desired torque si~nal which is a function of both the preselected flow rate signal and the speed signal.
Means compares the desired torque signal to the motor torque signal thereby to supply a comparison signal. Means applies a mot~r voltage to one or more of the winding stages at a tim~ in accordance with the comparison sig~al and commutates the winding stages in a preselected sequence to rotate the rotatable assembly whereby the blower is driven to maintain substantially constant air flow in the system at the prese-lected rate substantially independent of variations in the static pressure.
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l9bjw 2 01~ 0 9 03-LO-6262 GEN 9225 ~ PATENT
~rief Description of the Drawin~s Figure 1 is a block diagram of a preferred embodi-ment of an air handling system including the apparatus of the present invention.
Figùre 2 is a graph o~ speed along the ordinate versus torqu~ along the abscissa of 3 motor operating at various air flow rate demand levels under the control o~
apparatus ~f this inventioll.
~igure 3 is a schematic diagram of the comparison circuit of Figure 1.
Figure 4 is a schematic diagram of the circuit indi-cating to tha microproc~ssor the preset air flow rates and the value o~ constant kl indicating the charact~ristics of the air flow system.
Corresponding reference characters indicate corre-sponding parts throughout the several view of the drawings.
~etaile~ Descri~tio~ of the Preferred ~mho~ nt Rsferring to the drawings and particularly to Figure 1, roference character ln generally re~ers to an appa-ratus accordi~g to the invention for controlling a dynamoelectric machine such as motor 12. Motor 12 includ~s a sta-tionary as~embly 14 with a plurality o~ winding stages for carrying motor current and further includ~s a:rotatable assem-bly 15 in driving relation with a blower in an air handling : 25 system. As illustrated, rotatable assembly 16 is connected ; by drive shaft 18 to a squirrel cage blower 20 which is .within a contain~d space such as an air handling system 22.
The apparatus 10 provides control of the speed of blower 20 : over a range of static pressure variations within the air handling system to a maintain relative1y constant preselected -lsbjw , 2 01~ 5 09 03-LO-6262 aEN 9225 PATENT
rate of air flow in system 22. Although blower 20 is illus-trated as a squirrel cage blower~ it is contemplat~d that rokatable assembly 16 may be in drivirlg r~lation with any type o~ blade, fan, blower or other device for moving air in S air handling ~y~tem 22~
In ~eneral, apparatus 10 is aRsociated with a devic~ or system f or providing a preselected flow rate signal repre~enting the preselected air flow rate. For example, apparatus 10 may be associated with a thermostat or micro proc~ssor which is controlling opcration of the air handling system in response to sensors and op~rator input. In any case, apparatus 10 is adapted to receive a preselected air flow signal representin~ the preselected air flow rate.
Preferably, thiS signal has a dc voltage which is directly proportional to the preselected air flow ra~-e. In general, the signal may be variable or it may have one o~ several preset 1e~Q1S. For ~sample, in more sophisticated air handling ~y8tem3 which are controlled by mi~roprocessors, the preselected air ~1OW signal may vary over a range of, say, zero to five volts to represent a preselected air flow rate from 400 to 1300 CF~. Alternatively, many air handling systems have two or three levels o~ operation correspon~ing ; to a low ~pee~, a high speed and an override heating ~p~ed.
The low sp~ed may correspond to 400 CFM, the high speed to : 25 B00 C~M and the override heating speed to 1300 CFM. The preselected air flow signal would then take the form o~ one : o~ three voltage levels corresponding to these three dif-~ere~t presel~cted levels of air flow rates.
The preselected air flow signal is proYided to microp~ocessor 10 along with a ~peed or rpm signal represen-tative of the speed of motor 12. In general, apparatus 10 includes means for providing a speed signal representative of the speed of the motor such as integrated circuit 26. R~fer-e~ce character 26 re~ers to an integrated circuit (IC~ which ' ''', : , :
l9bjw 2 01 5 ~ ~ 9 03-LO-62 62 is generally a universal IC for use as a commutating ci~cuit in combination with an electronically commutated motor. Such an IC is described in coasslgned U.S. patent No. ~,500,821 to ~itting et al., incoxporated herein by referenca. IC 26 con-stitutes means for applying a motor voltage to one or more ofthe windi~g stages and for commutatin~ the winding stages in a praselected sequence to rotate the rotatahle assembly. In general, IC 26 has an input Ireg which receives a signal indicative of the desired torque or ai~ flow rato and defin-ing the periods during which the motor voltige should beapplied to the winding stages. IC 26 generally controls a plurality of power switching devices 28 which apply a voltage supplied by power supply 30 to the winding stages~ IC 26 controls power switches 28 to commutate the winding stages of motor 12 in a preselected sequence to rotate the rotatable assembly o~ the motor 12.
I~ one preferred ~mbodiment, IC 26 controls power switches 28 in accordance with the sensed back emf of the winding stages. ~y sensing the back emf, ~C 26 genera~es a tachometer signal or rpm signal which is representative of the motor speed. This signal is provided to microprocessor ; 10. MicroprocessQr 10 is responsive to both the rpm signal provid~d by IC 26 and the preselected air flow signal pro-vided by the air h2ndling system control. In response to these si~nals, microproces~or 24 generates a desir~d current : signal which is a fu~ction of both the preselected flow rate signal and the rpm signal. In effect, the desired current signal corresponds to a de~ired torque signal because the torque of the motor is dire~tly proportional to the motor 3Q current. In one pref~rred embodiment, the desired current signal takes the form of a pulse-width modulated (PWM) series of pulsas ha~ing a duty cycle which is a function of both the preselected flow rate signal and the speed iynal.
lYbj~ 2 01 ~ 0-~ 03-LO-6262 The desired current (torque) signal is compared by comparison circuit 32 to a moto~ current (torque) signal which represents the sensed motor current ~torque). The motor current signal is generated by a motor current s~n~or S 39 well known to o~e skilled in the art. For e~ample, motor current s~nsor 34 may be a shunt resistor connected to the primary power supply line of the voltage applied to the motor windings. Alternatively, the motor current ~ensor may be a sensor such as disclos~d in copendiny and coassigned U.S.
pat~nt application Serial No. 235,995 filed August 24, 1988, in~ented by William Archer entitled ~ethod and Apparatus for Sensing Direct Current of One Polarity in a Conductor and Electronically Commutated Motor Control Re~ponsive to Sense Motor Current. Altexnativ~ly, the motor current sensor may sense any parameter of the motor which is direc~ly propor-tional to motor torque.
I~ the event that the motor current signal repre-~ents a motor curr~nt which is less than the desired current signal, comparison circuit 32 provides a comparison signal to the Ir~g input of IC 26 which indicates that the motor volt-age should be continued to be applied to the motor windings.
When ~h~ motor current signal indicates that the motvr cur-rent is equal to the desired current signal or whenever the mo~or current sig~l indicates that th~ motor current is equal to or greater than the desir~d current signal, compari-so~ circuit 32 yenerate~ a comparison signal provided to the Ire~ input of IC 26 which indicates that the motor voltage should not be ap~lied any longer to the winding stages. In one pr~farred embo~iment, if the comparison signal is high, IC 26 applies the motor voltage to the winding stages and if the compari~on signal is low, IC 26 do~s not apply the motor voltage to the winding sta~es.
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l9bjw 2 0 ~ 5 ~ 0 9 03--LO-6262 In one preferred embodiment according to the inven-tion, microprocessor 24 implements a constant air flow algo-rithm to control the motor 12 according to the principle o~
speed compens~ted to~que. This type of control signi~icantly enhances the independence o~ the air ~low rate o~ the motor to static pressure within air handling system 22. As indi-cated ahove, depending on the typ~ of blow~r 20, changes in the static pressure within the air handling system 22 will result in changes in the speed of blower 20. The principle of speed compensated torque allows the motor to rotate the hlower to maintain air flow in the system 22 independent o~
variations in static pressure. In the past, the speed versus torque characteristics, such as suggested by Young in U.S.
patent No. 4,806,833, w~re all straigbt lines parallel to each other. The ~lope of these parallel lines was the same for all air ~low lavels such as illustrated in Figure 4 of the Young patent. In contrast, microprocessor 24 implements an algorithm so that the speed versus torgue characteristics for ~very air ~low level have a different slope. This aspect o~ the invention is illustrated in Figure 2. ~cept at low speeds which will be e~plained below, the speed torque char-acteristic for any given air flow rate is a straight line passing through the origin with a slope ~torque/speed) that i~ directly proportional to the level of air flow rate that is to be m~intai~ed. The proportionality constant depends on the ~ize of the blower wheel and the n~mber of hlade~. In tho curves illustrated Figure 2, it has been assumed th~t the blower 20 is a squirrel cage. As noted above, the speed torque charac~eristics may change depending on the type of blow~r being used and ~he type of system within which the blower is located.
In general, the desired current signal provided by microproc~ssor 24 comprises a pulse width modulated series of :, :
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, : : . . . . ' . : .
.: . ' : . : ', . '' .
l9bjw ~01 ~ 5 0 ~ o 3-L0-6262 pulses having a duty cycle which is defined by an algorithm in which the duty cycle is a function of the rpm signal and the preselected air flow signal. In particular, microproces-sor 24 opee~tes in accordance with the following algorithm:
T ~ klAS, wherein T equals the duty cycle of the series of pulses and is directly proportional to the desired torque (current) needed to maintain the preselected air flow rate, A
equals the pre~elected rate of air ~10w, S equals the motor speed and kl equals the proportionality constant representing the characteristics of the blower 20 in the air handling system 22.
At low speeds, to continue to maintain air flow, it has been found that the characteristic should preferably become con~tant torque in nature. At low speeds, the torque ; 15 is directly proportional to the square of the desired air flow le~el. At sp~eds abnve the maximum operating speed at r~i tm torque, the torque is rapidly reduced. In this case, the algorithm takes the following form:
T ~ Tmin ~or S ~ Slim~
T ~ -k3AS ~ C for Slim ~ S ~ Sma~
T ~ klAS for Sma~ 2 S >- ~k2~kl)A, and T ~ k2A2 for S 5 (k2/kl~A, wheroin T equals the duty cycle of the series of pulses, A
equals the preselected rate of air flow, S equals the motor speed, Sma~ equals the ma~imum operating speed at ma~imum torque, kl and k2 are constants representing the character-istics of the blower in the air handling system, k3 and C are constants relating to the torque reduction rate above Sm~
with k3 ~ C/ASmax - kl~ Slim is the speed limit, and Tmin is :, . : . . ... . . . .
, .... . .. . . .. .
. - . -, - . . ~ ,.
. - , , ., . . . , -,: ~ -, ': ' ' lsbjw 2 01~ ~ ~ 9 03-L0-6262 the minimum torque above the speed limit and is equal to ~k3~Slim + C.
The proportionality constant k~ at low speeds is again dependent on the characteristics o~ blower wheel and is g~nerally proportional to th~ proportionality constant kl.
In particular, it has been found itl many systems that the propo~tionality constant k2 is half the value o~ the constant kl at operating speeds. Although microprocessor 24 has been described as operating in accordance with an algorithm, one s~illed in the art will readily recognize that the micropro-cessor may also operate in accordance with a table defining the various speed torque characteristics of the system.
It is also readily apparent to one skilled i~ the art that the suggested algorithm, which is a multiple slope algorithm, is ~till an appro~imation of the ideal speed torque characteristics and that a more detailed or complex algorithm or table may be used to obtain a closer appro~ima-tion. The table would be generated i~ the ~ollowing manner.
A ~alue corresponding to each preselected àir ~10w rat~ and for each increment of motor speed wauld be calculated and stored within memory for access by the microprocessor.
Depending on the size of the table an~ the increments, such a table could provide a nonlinear or closer approximation of the idaal speed torque characteristics for esch preselected air flow rate.
It has be~n found that the suggested algorithm i5 significantly more complete and accurate than the si~gle slope approach suggested by Young in patent No. 4,8~Ç,833 and that such an algorithm opera~s over the~e~tire range o~
operation of the air handling system and is~not limited to a small range of air flow rates and static pressures as is the prior art. Furthermore, the al~orithm is universal and with changes to the proportionality constant to account for dif-ferent blower wheels and air handling systems, the apparatus .
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METHOD AND APPARATUS FOR CONTROLLING
A B~.OW~ MQTOR IN A~ AIR ~A~DI.ING SYST~
Fiel~ o~ the I~ve~tio~
This invention relates in general to systems for condltioning the temperature of a space and, in particular, to a Rystem ~or conditionlng air and for maintaining a pre-selected flow rate of the conditioned air through at least a part of ths system regardless of the static pressure therein, a method of operating a system for conditioning air, and a circuit.
Back~ro-ln~ of the InvRntio~
In th~ past, va~ious dif~erent techniques are bRliev~d to have been utilizsd in an attempt to flow air through a contained space of a system including an apparatus for conditioning the temperature of the air with the rate of such air flow being.related to the static pressure associated with ~uch system. Both th~ speed and torque of an electric motor driving a fan or blower to effect air flow through the system are affected by the static pressure in the system.
The rate of air flow ~CFM - cubic ~eet per minute) through the apparatus also a~fects the motor spasd and torque.
One approach of the past in~olved the rather laborious and time consuming matching of motor speed and torgue with th~ proper fan to appro~imate the desired air ~ 25 flow rat~ for the particular contai~ed spac~ and static ; pre~ure o~ the particular apparatus or system in which such apparatu~ was employ2d. However, this did not accommodate variation~ in the~static pressure in the system caused by alterations in the system such as ope~ing, closing or adjust-ing of a v~nt or the like connecting a conditioned space in air flow relation with the system~
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l9bjw 03-LO-6262 . . GE~ 9~25 201~0~ PATENT
If the fan or hlower utilized in the past was of the fan or blade typ~, a decrease in the static pr~ssure acting on such fan re~ulted in an increase in th~ speed of t~e Fan and tha elec~ric motor driving it. Conversely, if the static prcssure acting on the fan was increased, the speed of th~ fan and electric motor decreased. Thus, the speed of the fans a~d electric motors utilized in the past varied inversely with a variation of the static pressure in the system.
As recogni~ed in coassigned U.S. patent No.
4,806,833, incorporated herain by reference in its entirety, a d~crease in th~ statie pressure acting on a squirrel cage blower results in 2 decrease in the sp~ed of the squirrel eage blower and the electric motor driving it. Conversely, 15 if the ~tatic pressu~e acting on the squirrel cage blower is increased, the speed of the squirrel cage blower and its driving el~ctric motor is increased. Thus, it was found that the speed o~ th~ squirrel eage blower and its dri~ing elec-tric motor varies directly with a variation in the static pressure. Accordingly, U.S. patent No. 4,806,~33 discloses a : method of operating a system for conditioning air including a variable speed hlower ~or flowing the conditio~ed air through a contain~d space having a static pressure therein. In this : sys~em, the ~~~ed of the blower is set to a~fect a prese-lected flow rate at an e~isting st~tic pressure in th~ con-tained space and the sp~ed of the blower is altered only in respon~ to a variation in the static pressure and only i~
follo~ing relation with the static pressure variation. The spe~d alteration of the blower is sensed, and the speed of th~ blower is altered in following relation with the sensed speed alteration to establi~h the preselected flow rate through the contained space at the vari~d static pressure acting on the blower.
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, lsbiw 2 01~ 5 09 03-Lo-6262 GEN 9225 PATENr Although this approach is an improvement over the prior art, it is only a rough appro~imation o~ the charac~er-istics needed to achieve constant air flow with respect to changes in static pressure. In general, the systems of the prior art worked reasonably well over a limited range of air ~10ws and static pressures by employing a singl~ slope speed comp~nsation techniqu~. It has now been re~ognized that a much more accu.rate approach to providing sp~ed compensated torgue which can he implemented in an air handli.ng system is required. Such speed compensated torque would then allow the blow~r motor to maintain air flow in the system ind~pendent o~ variations in the static pressure in the duct work.
~mm~rY of the I~nkio~
~mong the several objects of the present invention may be noted the provision of an improved system for condi-tioning air and for maintaining a preselected air ~low rate of the conditioned air through at least a part of the system regardle~s o~ the static pressure therein, an improved method of opera~ing the system, and an improved circuit which will o~ercome the ahove-discussed disadvantages or undesirable features as well as others, of the prior art; the provision of such improved sy~tem and method in which the preselected flow rate is accurately controlled; the provision of such improved system and method in which wide variations in the ; 25 static pressure are readily accommodated; the pro~ision of such improved system and method in which the torque of a a dynamoelectric ~achine driving blower means is altered with variations in the speed of the motor to maintain constant air flow rat~ independent of static pressure on the blower means;
~0 the provision of such improved system and method in which the energi2ation of a dynamoelectric machine is adjustably regu-lated in order to maintain the preselected flow rate at static l9bjw 03~LO-6262 GEN 9225 2 015 5 0 9 PATE~T
pressure variations acting on the blower maans; and the pro-vision of such improved system, method and circuit u~ilizing a microprocessor and oth~r component parts which are simple in design, easily assembled and economically manu~actured.
The~s as well as other ohjects and advantageous features of the pr~sent invention will be in part apparent and in part pointed out hereinafter.
In general, an apparatus is provided in one form of the invention for controlling a dynamoelectric machine such as a ~otor having a stationary assembly with a plurality of winding stages for carrying motor current and further having a~rotatable assembly in driving relation with a blower in an air handling syst2m. The apparatus provides control of the blower torque over a range o~ static pressure variations to lS maintain relatively constant preselected rate of air f low in th~ system. Th~ apparatus is adapted to receive a preselected flow rate Rignal represent~ng the preselected air flow rate.
Means provides a mo~or torque signal representative of the motor torque. Means provides a speed signal representative 20 of thè speed of the motor. A microprocessor which is respon-sive to both the preselected flow rate signal and t~e ~peed signal generates a desired torque si~nal which is a function of both the preselected flow rate signal and the speed signal.
Means compares the desired torque signal to the motor torque signal thereby to supply a comparison signal. Means applies a mot~r voltage to one or more of the winding stages at a tim~ in accordance with the comparison sig~al and commutates the winding stages in a preselected sequence to rotate the rotatable assembly whereby the blower is driven to maintain substantially constant air flow in the system at the prese-lected rate substantially independent of variations in the static pressure.
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l9bjw 2 01~ 0 9 03-LO-6262 GEN 9225 ~ PATENT
~rief Description of the Drawin~s Figure 1 is a block diagram of a preferred embodi-ment of an air handling system including the apparatus of the present invention.
Figùre 2 is a graph o~ speed along the ordinate versus torqu~ along the abscissa of 3 motor operating at various air flow rate demand levels under the control o~
apparatus ~f this inventioll.
~igure 3 is a schematic diagram of the comparison circuit of Figure 1.
Figure 4 is a schematic diagram of the circuit indi-cating to tha microproc~ssor the preset air flow rates and the value o~ constant kl indicating the charact~ristics of the air flow system.
Corresponding reference characters indicate corre-sponding parts throughout the several view of the drawings.
~etaile~ Descri~tio~ of the Preferred ~mho~ nt Rsferring to the drawings and particularly to Figure 1, roference character ln generally re~ers to an appa-ratus accordi~g to the invention for controlling a dynamoelectric machine such as motor 12. Motor 12 includ~s a sta-tionary as~embly 14 with a plurality o~ winding stages for carrying motor current and further includ~s a:rotatable assem-bly 15 in driving relation with a blower in an air handling : 25 system. As illustrated, rotatable assembly 16 is connected ; by drive shaft 18 to a squirrel cage blower 20 which is .within a contain~d space such as an air handling system 22.
The apparatus 10 provides control of the speed of blower 20 : over a range of static pressure variations within the air handling system to a maintain relative1y constant preselected -lsbjw , 2 01~ 5 09 03-LO-6262 aEN 9225 PATENT
rate of air flow in system 22. Although blower 20 is illus-trated as a squirrel cage blower~ it is contemplat~d that rokatable assembly 16 may be in drivirlg r~lation with any type o~ blade, fan, blower or other device for moving air in S air handling ~y~tem 22~
In ~eneral, apparatus 10 is aRsociated with a devic~ or system f or providing a preselected flow rate signal repre~enting the preselected air flow rate. For example, apparatus 10 may be associated with a thermostat or micro proc~ssor which is controlling opcration of the air handling system in response to sensors and op~rator input. In any case, apparatus 10 is adapted to receive a preselected air flow signal representin~ the preselected air flow rate.
Preferably, thiS signal has a dc voltage which is directly proportional to the preselected air flow ra~-e. In general, the signal may be variable or it may have one o~ several preset 1e~Q1S. For ~sample, in more sophisticated air handling ~y8tem3 which are controlled by mi~roprocessors, the preselected air ~1OW signal may vary over a range of, say, zero to five volts to represent a preselected air flow rate from 400 to 1300 CF~. Alternatively, many air handling systems have two or three levels o~ operation correspon~ing ; to a low ~pee~, a high speed and an override heating ~p~ed.
The low sp~ed may correspond to 400 CFM, the high speed to : 25 B00 C~M and the override heating speed to 1300 CFM. The preselected air flow signal would then take the form o~ one : o~ three voltage levels corresponding to these three dif-~ere~t presel~cted levels of air flow rates.
The preselected air flow signal is proYided to microp~ocessor 10 along with a ~peed or rpm signal represen-tative of the speed of motor 12. In general, apparatus 10 includes means for providing a speed signal representative of the speed of the motor such as integrated circuit 26. R~fer-e~ce character 26 re~ers to an integrated circuit (IC~ which ' ''', : , :
l9bjw 2 01 5 ~ ~ 9 03-LO-62 62 is generally a universal IC for use as a commutating ci~cuit in combination with an electronically commutated motor. Such an IC is described in coasslgned U.S. patent No. ~,500,821 to ~itting et al., incoxporated herein by referenca. IC 26 con-stitutes means for applying a motor voltage to one or more ofthe windi~g stages and for commutatin~ the winding stages in a praselected sequence to rotate the rotatahle assembly. In general, IC 26 has an input Ireg which receives a signal indicative of the desired torque or ai~ flow rato and defin-ing the periods during which the motor voltige should beapplied to the winding stages. IC 26 generally controls a plurality of power switching devices 28 which apply a voltage supplied by power supply 30 to the winding stages~ IC 26 controls power switches 28 to commutate the winding stages of motor 12 in a preselected sequence to rotate the rotatable assembly o~ the motor 12.
I~ one preferred ~mbodiment, IC 26 controls power switches 28 in accordance with the sensed back emf of the winding stages. ~y sensing the back emf, ~C 26 genera~es a tachometer signal or rpm signal which is representative of the motor speed. This signal is provided to microprocessor ; 10. MicroprocessQr 10 is responsive to both the rpm signal provid~d by IC 26 and the preselected air flow signal pro-vided by the air h2ndling system control. In response to these si~nals, microproces~or 24 generates a desir~d current : signal which is a fu~ction of both the preselected flow rate signal and the rpm signal. In effect, the desired current signal corresponds to a de~ired torque signal because the torque of the motor is dire~tly proportional to the motor 3Q current. In one pref~rred embodiment, the desired current signal takes the form of a pulse-width modulated (PWM) series of pulsas ha~ing a duty cycle which is a function of both the preselected flow rate signal and the speed iynal.
lYbj~ 2 01 ~ 0-~ 03-LO-6262 The desired current (torque) signal is compared by comparison circuit 32 to a moto~ current (torque) signal which represents the sensed motor current ~torque). The motor current signal is generated by a motor current s~n~or S 39 well known to o~e skilled in the art. For e~ample, motor current s~nsor 34 may be a shunt resistor connected to the primary power supply line of the voltage applied to the motor windings. Alternatively, the motor current ~ensor may be a sensor such as disclos~d in copendiny and coassigned U.S.
pat~nt application Serial No. 235,995 filed August 24, 1988, in~ented by William Archer entitled ~ethod and Apparatus for Sensing Direct Current of One Polarity in a Conductor and Electronically Commutated Motor Control Re~ponsive to Sense Motor Current. Altexnativ~ly, the motor current sensor may sense any parameter of the motor which is direc~ly propor-tional to motor torque.
I~ the event that the motor current signal repre-~ents a motor curr~nt which is less than the desired current signal, comparison circuit 32 provides a comparison signal to the Ir~g input of IC 26 which indicates that the motor volt-age should be continued to be applied to the motor windings.
When ~h~ motor current signal indicates that the motvr cur-rent is equal to the desired current signal or whenever the mo~or current sig~l indicates that th~ motor current is equal to or greater than the desir~d current signal, compari-so~ circuit 32 yenerate~ a comparison signal provided to the Ire~ input of IC 26 which indicates that the motor voltage should not be ap~lied any longer to the winding stages. In one pr~farred embo~iment, if the comparison signal is high, IC 26 applies the motor voltage to the winding stages and if the compari~on signal is low, IC 26 do~s not apply the motor voltage to the winding sta~es.
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l9bjw 2 0 ~ 5 ~ 0 9 03--LO-6262 In one preferred embodiment according to the inven-tion, microprocessor 24 implements a constant air flow algo-rithm to control the motor 12 according to the principle o~
speed compens~ted to~que. This type of control signi~icantly enhances the independence o~ the air ~low rate o~ the motor to static pressure within air handling system 22. As indi-cated ahove, depending on the typ~ of blow~r 20, changes in the static pressure within the air handling system 22 will result in changes in the speed of blower 20. The principle of speed compensated torque allows the motor to rotate the hlower to maintain air flow in the system 22 independent o~
variations in static pressure. In the past, the speed versus torque characteristics, such as suggested by Young in U.S.
patent No. 4,806,833, w~re all straigbt lines parallel to each other. The ~lope of these parallel lines was the same for all air ~low lavels such as illustrated in Figure 4 of the Young patent. In contrast, microprocessor 24 implements an algorithm so that the speed versus torgue characteristics for ~very air ~low level have a different slope. This aspect o~ the invention is illustrated in Figure 2. ~cept at low speeds which will be e~plained below, the speed torque char-acteristic for any given air flow rate is a straight line passing through the origin with a slope ~torque/speed) that i~ directly proportional to the level of air flow rate that is to be m~intai~ed. The proportionality constant depends on the ~ize of the blower wheel and the n~mber of hlade~. In tho curves illustrated Figure 2, it has been assumed th~t the blower 20 is a squirrel cage. As noted above, the speed torque charac~eristics may change depending on the type of blow~r being used and ~he type of system within which the blower is located.
In general, the desired current signal provided by microproc~ssor 24 comprises a pulse width modulated series of :, :
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.: . ' : . : ', . '' .
l9bjw ~01 ~ 5 0 ~ o 3-L0-6262 pulses having a duty cycle which is defined by an algorithm in which the duty cycle is a function of the rpm signal and the preselected air flow signal. In particular, microproces-sor 24 opee~tes in accordance with the following algorithm:
T ~ klAS, wherein T equals the duty cycle of the series of pulses and is directly proportional to the desired torque (current) needed to maintain the preselected air flow rate, A
equals the pre~elected rate of air ~10w, S equals the motor speed and kl equals the proportionality constant representing the characteristics of the blower 20 in the air handling system 22.
At low speeds, to continue to maintain air flow, it has been found that the characteristic should preferably become con~tant torque in nature. At low speeds, the torque ; 15 is directly proportional to the square of the desired air flow le~el. At sp~eds abnve the maximum operating speed at r~i tm torque, the torque is rapidly reduced. In this case, the algorithm takes the following form:
T ~ Tmin ~or S ~ Slim~
T ~ -k3AS ~ C for Slim ~ S ~ Sma~
T ~ klAS for Sma~ 2 S >- ~k2~kl)A, and T ~ k2A2 for S 5 (k2/kl~A, wheroin T equals the duty cycle of the series of pulses, A
equals the preselected rate of air flow, S equals the motor speed, Sma~ equals the ma~imum operating speed at ma~imum torque, kl and k2 are constants representing the character-istics of the blower in the air handling system, k3 and C are constants relating to the torque reduction rate above Sm~
with k3 ~ C/ASmax - kl~ Slim is the speed limit, and Tmin is :, . : . . ... . . . .
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. - , , ., . . . , -,: ~ -, ': ' ' lsbjw 2 01~ ~ ~ 9 03-L0-6262 the minimum torque above the speed limit and is equal to ~k3~Slim + C.
The proportionality constant k~ at low speeds is again dependent on the characteristics o~ blower wheel and is g~nerally proportional to th~ proportionality constant kl.
In particular, it has been found itl many systems that the propo~tionality constant k2 is half the value o~ the constant kl at operating speeds. Although microprocessor 24 has been described as operating in accordance with an algorithm, one s~illed in the art will readily recognize that the micropro-cessor may also operate in accordance with a table defining the various speed torque characteristics of the system.
It is also readily apparent to one skilled i~ the art that the suggested algorithm, which is a multiple slope algorithm, is ~till an appro~imation of the ideal speed torque characteristics and that a more detailed or complex algorithm or table may be used to obtain a closer appro~ima-tion. The table would be generated i~ the ~ollowing manner.
A ~alue corresponding to each preselected àir ~10w rat~ and for each increment of motor speed wauld be calculated and stored within memory for access by the microprocessor.
Depending on the size of the table an~ the increments, such a table could provide a nonlinear or closer approximation of the idaal speed torque characteristics for esch preselected air flow rate.
It has be~n found that the suggested algorithm i5 significantly more complete and accurate than the si~gle slope approach suggested by Young in patent No. 4,8~Ç,833 and that such an algorithm opera~s over the~e~tire range o~
operation of the air handling system and is~not limited to a small range of air flow rates and static pressures as is the prior art. Furthermore, the al~orithm is universal and with changes to the proportionality constant to account for dif-ferent blower wheels and air handling systems, the apparatus .
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2 ~ 9 lsbjw 03-L0 6262 according to the invention can b~ used in any type of blower system. For e~ample, this system can be succes~~ull~ imple-mented fo~ blowers used in ~urnaces, in heat pumps, ln cen-tral air conditioning systems and in other air handling systems with capacities of varying range and for different manufacturers.
The microprocessor may also provide protection against a locked rotatable assembly by functi~ning as means for disabling operation of the motor in the ~VBnt that a speed slg~al is not provided to the microprocessor. In general, if an RPM signal is not provid~d to the microproces-sor within a preset period of time, say lZ seconds, after a desired current (torque) signal is generated, the micropro-cessor can shut down to prevent motor damage. In one pre-~erred embodiment wherein the microprocessor provides a soft start, i.e., a slowly increasing desired torque signal, the .-microproces~or resets if an RPM signal is not detected after 12 saconds. After 8 re~et cycles, the microprocessor shuts down motor oparation.
Considering now th~ graph of Figure 2, there is shown a ~quen~e of solid ~ines illustrated in a relationship betwe~n the speed and torque for a typical air conditioning system blower operated by motor 12 connected ~or driving sguirral ca~e blower 20 in system 22 built in accordance with the preferr~d embodiment of the invention~ Each of the solid lines on the graph r~present~ a constant CFM line. Each line illu~tratee the near linear relationship between spe~d and torque and the variation in speed and torque as static pres-sure increases for any given CFM. At low speeds, each solid line takes the form of a vertical line essentially defining a constant torque (current). For safety, the torgue above the m~ op~rating speed ~Smax) at ~he torque limit ~T~na~) is reduced to a minimum torque level (Tmin) which maintains air .. , , -, . - . :. .
- ' - : ' - :
- : , lgbjw 2 01 5 5 ~ 9 03-L0-6262 flow. This defines the operating speed limit illustrated in Fi~ure 2. This reduction above th~ maximum operating speed is accomplished by the microproce~sor and is de~ined by the algorithm. The setting o~ the torque limit depends on the system and safety factors and will be explained below in greater det~il.
Re~erring to Figure 3, one preferred embodiment o~
compari~on circuit 32 according to the inventio~ is illus-trated. The preselected air ~10w signal, as a PWM signal, is provided to the noninverting input 11 of comparator 60 which functions as a buffer. Comparator 60 is an open collector comparator well known in th~ prior art providing a grounded output when the dc voltage applied to the noninverting input is greater than the dc voltage applied to the inverting input.
A re~eren~e voltags is applied to tha inverting input 10 of comparator 60 generated by t~Q voltage divider formed by rcsistors R103 and ~10~. Output 13 of comparator 60 e~sen-tially ~ollows input 11. A dc voltage is applied to capaci-tor C22 as diuided by resistors R102 and R56. Output 13 essentially p2rmi~s capacitor C22 to charge whenever the PWM
signal applied to input 11 is high so that the charge on capacitor C22 represents the duty cy~le of the PWM slg~al.
In other words, capacitor C22 functions as an averager to produc~ a voltage repre~entative of the duty cycle o~ the PWM
signal applied tv input 11. This is beeause tha duty cycle : of the PWM signal determine~ the amount of char~ing of capac-itor C22. The ~ m voltage level on capacitor C22 is adjusted by resistor RS7. Terminal Sl- repre~ents the nega-tive sid~ of the shunt resistor. The vo~tage o~ the Sl-terminal as adjusted by resistor R62 constitu~es a bias point or re~erence for comparison of the motor current. This volt-age is summed with the adiusted voltage provided a~ter resis-tor R57 and applied to th~ noninv~rting input 7 of comparator , ~ 13 ~ .
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lgbjw 2 01~ 5 ~ ~ 03-L0-6262 62. This voltage is further ad~usted by applying a 5 volt bias signal thsough resistor R94.
The inverting input 6 of comparator 62 is then pro-vided ~ith a signal r~presenting the motor curren~. In par-ticular~ termillal Sl+ is connected to the positive side of~he 3hunt resistor measuring the motor current and is applied to ~he inver~ing input 6 of comparator 62 as ad~usted by the 5 volt bias s~g~al appliad through resistor R58. Capacitors C23, C24 and C25 provide noise filtering.
As a result, comparator 62 receives a reference adjust~d signal at its noninverting input 7 which represents the duty cycle o~ the PWM signal, i.e., the d~sired current, and the inverting input 6 receives a signal representative of the motor curr~nt signal, i.e., the motor current. Compara-tor 62 compares these signals and provides a comparison si~nal at its output 9 representative of the dif~erence. When the signal at input 7 is higher than the signal at input 6, indi-cating that the motor curren} is less than desired, output 9 goes high to apply voltage VD~ through resis~or R60 and resis-tor R61 to the Ir~g input o~ IC 26. This indicates to the IC26 to apply motor voltage to the winding stages. In the event that signal applied to input 6 is greater than the signal applied to input 7, indicating that th~ motor current is greater than the desired current, output 9 ~oes low and is grounded to indicate to IC 26 that th~ voltage should not be applied to th~ motor windings. Capacitor CZ7 provides fur-~ ther noise filtering. --'~ Resistors R56 and R57 determiQe the ~ voltage to which capacitor C22 can be charged. This ma~ir~ voltage ess~ntially defines the torqu~ limit of the system as il1us-trated in Figure 2. In other words, selecting values of resistors Rg6 and ~57 selects the dc voltage to which capaci~
tor C22 g~ts charged at a 100% duty cycle. This m~
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l9bjw 2 015 5 ~ 9 03-LO-626Z
voltage corr~sponds to the ma~imum torque. To some e~tent, resistors R62 and R94 adjust this ma~imum torque limit.
Re~erring to figure 4, circuitry is illustratad for indicating to microprocesso.r 24 one or more pr~set valu~s o~
S the air ~10w rate and the value of the constant kl. In the case o~ a continuously variable ai~ flow control, microproces-sor 24 is provided with the preselected air flow rate signal in the form of a puls~ width modulated series of pulses hav-ing a duty cycle representative of the desired air flow rate.
In the case of continuously variable air Flow control, the presets define the minimum and maximum air flow rates. The duty o~ the air flow rate si~nals determines the desired air flow le~l between the minimum and maximum air flow rate~ In the ca~e o~ three speed control, the presets de~ine the high (HI), low (LO) and heat (~iEAT) air flow levels. Essentially, thes~ pr~sets are resistors R27-R36 which are connected to the HEAT, ~0 AND HI inputs to microprocessor 24 by field selectable jumpers.
The microprocessor determines the value of the rasistors connected to the HEAT, LO AND HI inputs in the following manner. Oscillator 80 generates an oscillating signal at pin 14. Oscillator 80 comprises comparator 82 biased by the ~5 volts applied through resistor R22 to its noninv~rting input 9 and the +5 volts applied through resis-~5 tor R~4 to its output. Capacitor C15 in parallel withresistor R26 form an RC circuit between ground and the invent-ing input ~ and output 14 of comparator 82. Resistor R2S
adjusts this feedback loop to provide an oscillating output.
The noninverting input 3 oscillates due to feedback provided by resistor R23 as adjusted by resistor R2~ and the res s-tance on line 84. Therefore, the frequency of the oscillating signal on pin 14 depends, in part, upon the re~i~tance tied to input g via line 84. Microprocessor 24 selectively ,: ' . ' , l9bjw 03--LO 6262 GEN 9~:25 2 ~ 5 ~ 9 PATE~1T
grounds output~ B7-83 in order to measure at the timer input the oscillating frequency corresponding to the HEAT, LO, HI, k~ and calibrating resistor. This ~requency measurement is usually accompllshed during periods that the fan is not S operating.
Tha value oE kl is assigned by the value of resis-tor R37. Resistor R38 provicles a calibrating reference for comparison.
In Vi2W of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.
~ As various changes could be made in the above con-structions without departing from the scope of tbe invention, it is intended that all matter contained in the above d~scription or shown in the accompanying drawings shall be intarpreted as illustrative and not in a limiting sense.
The microprocessor may also provide protection against a locked rotatable assembly by functi~ning as means for disabling operation of the motor in the ~VBnt that a speed slg~al is not provided to the microprocessor. In general, if an RPM signal is not provid~d to the microproces-sor within a preset period of time, say lZ seconds, after a desired current (torque) signal is generated, the micropro-cessor can shut down to prevent motor damage. In one pre-~erred embodiment wherein the microprocessor provides a soft start, i.e., a slowly increasing desired torque signal, the .-microproces~or resets if an RPM signal is not detected after 12 saconds. After 8 re~et cycles, the microprocessor shuts down motor oparation.
Considering now th~ graph of Figure 2, there is shown a ~quen~e of solid ~ines illustrated in a relationship betwe~n the speed and torque for a typical air conditioning system blower operated by motor 12 connected ~or driving sguirral ca~e blower 20 in system 22 built in accordance with the preferr~d embodiment of the invention~ Each of the solid lines on the graph r~present~ a constant CFM line. Each line illu~tratee the near linear relationship between spe~d and torque and the variation in speed and torque as static pres-sure increases for any given CFM. At low speeds, each solid line takes the form of a vertical line essentially defining a constant torque (current). For safety, the torgue above the m~ op~rating speed ~Smax) at ~he torque limit ~T~na~) is reduced to a minimum torque level (Tmin) which maintains air .. , , -, . - . :. .
- ' - : ' - :
- : , lgbjw 2 01 5 5 ~ 9 03-L0-6262 flow. This defines the operating speed limit illustrated in Fi~ure 2. This reduction above th~ maximum operating speed is accomplished by the microproce~sor and is de~ined by the algorithm. The setting o~ the torque limit depends on the system and safety factors and will be explained below in greater det~il.
Re~erring to Figure 3, one preferred embodiment o~
compari~on circuit 32 according to the inventio~ is illus-trated. The preselected air ~10w signal, as a PWM signal, is provided to the noninverting input 11 of comparator 60 which functions as a buffer. Comparator 60 is an open collector comparator well known in th~ prior art providing a grounded output when the dc voltage applied to the noninverting input is greater than the dc voltage applied to the inverting input.
A re~eren~e voltags is applied to tha inverting input 10 of comparator 60 generated by t~Q voltage divider formed by rcsistors R103 and ~10~. Output 13 of comparator 60 e~sen-tially ~ollows input 11. A dc voltage is applied to capaci-tor C22 as diuided by resistors R102 and R56. Output 13 essentially p2rmi~s capacitor C22 to charge whenever the PWM
signal applied to input 11 is high so that the charge on capacitor C22 represents the duty cy~le of the PWM slg~al.
In other words, capacitor C22 functions as an averager to produc~ a voltage repre~entative of the duty cycle o~ the PWM
signal applied tv input 11. This is beeause tha duty cycle : of the PWM signal determine~ the amount of char~ing of capac-itor C22. The ~ m voltage level on capacitor C22 is adjusted by resistor RS7. Terminal Sl- repre~ents the nega-tive sid~ of the shunt resistor. The vo~tage o~ the Sl-terminal as adjusted by resistor R62 constitu~es a bias point or re~erence for comparison of the motor current. This volt-age is summed with the adiusted voltage provided a~ter resis-tor R57 and applied to th~ noninv~rting input 7 of comparator , ~ 13 ~ .
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lgbjw 2 01~ 5 ~ ~ 03-L0-6262 62. This voltage is further ad~usted by applying a 5 volt bias signal thsough resistor R94.
The inverting input 6 of comparator 62 is then pro-vided ~ith a signal r~presenting the motor curren~. In par-ticular~ termillal Sl+ is connected to the positive side of~he 3hunt resistor measuring the motor current and is applied to ~he inver~ing input 6 of comparator 62 as ad~usted by the 5 volt bias s~g~al appliad through resistor R58. Capacitors C23, C24 and C25 provide noise filtering.
As a result, comparator 62 receives a reference adjust~d signal at its noninverting input 7 which represents the duty cycle o~ the PWM signal, i.e., the d~sired current, and the inverting input 6 receives a signal representative of the motor curr~nt signal, i.e., the motor current. Compara-tor 62 compares these signals and provides a comparison si~nal at its output 9 representative of the dif~erence. When the signal at input 7 is higher than the signal at input 6, indi-cating that the motor curren} is less than desired, output 9 goes high to apply voltage VD~ through resis~or R60 and resis-tor R61 to the Ir~g input o~ IC 26. This indicates to the IC26 to apply motor voltage to the winding stages. In the event that signal applied to input 6 is greater than the signal applied to input 7, indicating that th~ motor current is greater than the desired current, output 9 ~oes low and is grounded to indicate to IC 26 that th~ voltage should not be applied to th~ motor windings. Capacitor CZ7 provides fur-~ ther noise filtering. --'~ Resistors R56 and R57 determiQe the ~ voltage to which capacitor C22 can be charged. This ma~ir~ voltage ess~ntially defines the torqu~ limit of the system as il1us-trated in Figure 2. In other words, selecting values of resistors Rg6 and ~57 selects the dc voltage to which capaci~
tor C22 g~ts charged at a 100% duty cycle. This m~
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l9bjw 2 015 5 ~ 9 03-LO-626Z
voltage corr~sponds to the ma~imum torque. To some e~tent, resistors R62 and R94 adjust this ma~imum torque limit.
Re~erring to figure 4, circuitry is illustratad for indicating to microprocesso.r 24 one or more pr~set valu~s o~
S the air ~10w rate and the value of the constant kl. In the case o~ a continuously variable ai~ flow control, microproces-sor 24 is provided with the preselected air flow rate signal in the form of a puls~ width modulated series of pulses hav-ing a duty cycle representative of the desired air flow rate.
In the case of continuously variable air Flow control, the presets define the minimum and maximum air flow rates. The duty o~ the air flow rate si~nals determines the desired air flow le~l between the minimum and maximum air flow rate~ In the ca~e o~ three speed control, the presets de~ine the high (HI), low (LO) and heat (~iEAT) air flow levels. Essentially, thes~ pr~sets are resistors R27-R36 which are connected to the HEAT, ~0 AND HI inputs to microprocessor 24 by field selectable jumpers.
The microprocessor determines the value of the rasistors connected to the HEAT, LO AND HI inputs in the following manner. Oscillator 80 generates an oscillating signal at pin 14. Oscillator 80 comprises comparator 82 biased by the ~5 volts applied through resistor R22 to its noninv~rting input 9 and the +5 volts applied through resis-~5 tor R~4 to its output. Capacitor C15 in parallel withresistor R26 form an RC circuit between ground and the invent-ing input ~ and output 14 of comparator 82. Resistor R2S
adjusts this feedback loop to provide an oscillating output.
The noninverting input 3 oscillates due to feedback provided by resistor R23 as adjusted by resistor R2~ and the res s-tance on line 84. Therefore, the frequency of the oscillating signal on pin 14 depends, in part, upon the re~i~tance tied to input g via line 84. Microprocessor 24 selectively ,: ' . ' , l9bjw 03--LO 6262 GEN 9~:25 2 ~ 5 ~ 9 PATE~1T
grounds output~ B7-83 in order to measure at the timer input the oscillating frequency corresponding to the HEAT, LO, HI, k~ and calibrating resistor. This ~requency measurement is usually accompllshed during periods that the fan is not S operating.
Tha value oE kl is assigned by the value of resis-tor R37. Resistor R38 provicles a calibrating reference for comparison.
In Vi2W of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.
~ As various changes could be made in the above con-structions without departing from the scope of tbe invention, it is intended that all matter contained in the above d~scription or shown in the accompanying drawings shall be intarpreted as illustrative and not in a limiting sense.
Claims (28)
1. Apparatus for controlling an air handling system including a motor having a stationary assembly with a plurality of winding stage for carrying motor current and further having a rotatable assembly in driving relation with a blower in the air handling system the system further including means for generating a desired air flow rate signal which varies as a function of a desired rate of air flow, the apparatus providing control of the blower speed over a range of static pressure variations to maintain the rate of air flow in the system at substantially the desired air flow rate, the apparatus comprising:
means for providing a motor torque signal representative of the torque of the motor;
means for providing a speed signal representative of the speed of the motor;
a microprocessor, responsive to both the desired air flow rate signal and the speed signal for generating a desired torque signal which is a function of both the desired air flow rate signal and the speed signal;
means for comparing the desired torque signal to the motor torque signal and for supplying a comparison signal in response to the comparison; and means for applying a motor voltage to one or more of the winding stages at a time in accordance with the comparison signal and for commutating the winding stages in a preselected sequence to rotate the rotatable assembly whereby the blower is driven by varying the motor torque according to motor speed to maintain air flow in the system at substantially the desired rate of air flow substantially independent of variations in the static pressure.
means for providing a motor torque signal representative of the torque of the motor;
means for providing a speed signal representative of the speed of the motor;
a microprocessor, responsive to both the desired air flow rate signal and the speed signal for generating a desired torque signal which is a function of both the desired air flow rate signal and the speed signal;
means for comparing the desired torque signal to the motor torque signal and for supplying a comparison signal in response to the comparison; and means for applying a motor voltage to one or more of the winding stages at a time in accordance with the comparison signal and for commutating the winding stages in a preselected sequence to rotate the rotatable assembly whereby the blower is driven by varying the motor torque according to motor speed to maintain air flow in the system at substantially the desired rate of air flow substantially independent of variations in the static pressure.
2. The apparatus of claim 1, wherein the desired torque signs generated by said microprocessor comprises a pulse width modulated (PWM) series of pulses having a duty cycle which is a function of both the desired air flow rate signal and the speed signals.
3. The apparatus of claim 2 wherein the duty cycle of the PWM series of pulses is defined by an algorithm in which the duty cycle is a linear function of the speed signal and the desired air flow rate signals and wherein the linear function passes through the origin.
4. The apparatus of claim 3, wherein said microprocessor operates in accordance with the following algorithm;
T = k1AS, wherein T equals the duty cycle of the series of pulps A equals the desired rate of air flow S equals the motor speed and k1 equals a constant representing the characteristics of the blower in the air handling systems.
T = k1AS, wherein T equals the duty cycle of the series of pulps A equals the desired rate of air flow S equals the motor speed and k1 equals a constant representing the characteristics of the blower in the air handling systems.
5. The apparatus of claim 3 wherein said microprocessor operates in accordance with the following algorithm;
T = k1,AS for S2~(k2/k1) A, and T = k2A2 for S2~(k2/k1) A, wherein T equals the duty cycle of the series of pulses, A equals the desired rate of air flow, S equals the motor speed and k1 and k2 are constants representing the characteristics of the blower in the air handling system.
T = k1,AS for S2~(k2/k1) A, and T = k2A2 for S2~(k2/k1) A, wherein T equals the duty cycle of the series of pulses, A equals the desired rate of air flow, S equals the motor speed and k1 and k2 are constants representing the characteristics of the blower in the air handling system.
6. The apparatus of claim 5, wherein k2 is proportional to k1
7. The apparatus of claim 6, further comprising means for indicating the value of k1 said microprocessor including an oscillator and means for varying the frequency of the oscillator as a function of the value of k1-
8. The apparatus of claim 3 wherein said microprocessor operates in accordance with the following algorithm:
T = -k3AS + C for S~ Smax and T = k,AS for Smax~ S~(k2/k1)A, and T = k2A2 for S~(k2/k1)A
wherein T equals the duty cycle of the series and pulses A equals the desired rate of air flow S equals the motor speed Smax equals the maximum operating speed at maximum torque k1 and k2 are constants representing the characterics a of the blower in the air handling system and k3 and C are constants relating to the torque reduction rate above Sm~ with k3 = C/ASm~ - k1.
T = -k3AS + C for S~ Smax and T = k,AS for Smax~ S~(k2/k1)A, and T = k2A2 for S~(k2/k1)A
wherein T equals the duty cycle of the series and pulses A equals the desired rate of air flow S equals the motor speed Smax equals the maximum operating speed at maximum torque k1 and k2 are constants representing the characterics a of the blower in the air handling system and k3 and C are constants relating to the torque reduction rate above Sm~ with k3 = C/ASm~ - k1.
9. The apparatus of claim 3 wherein said microprocessor operates in accordance with the following algorithms:
T = Tmin for S~ Slim T = k3 AS + C for Slim~ S~max T = k1 AS for Smax ~ S~ (k2/k1) A, and T = k2A2forS~(k2/k1)A~
wherein T equals the duty cycle of the series of pulses A equals the desired rate of air flow S equals the motor speed Smax equals the maximum operating speed at maximum torque k1 and k2 are constants representing the characteristics of the blower in the air handling system k3 and C are constants relating to the torque reduction rate above Smax with k3 = C/ASmax - k1, Slim is the speed limit, and Tmin is the minimum torque above the speed limit and is equal to - k3 ASlim + C.
T = Tmin for S~ Slim T = k3 AS + C for Slim~ S~max T = k1 AS for Smax ~ S~ (k2/k1) A, and T = k2A2forS~(k2/k1)A~
wherein T equals the duty cycle of the series of pulses A equals the desired rate of air flow S equals the motor speed Smax equals the maximum operating speed at maximum torque k1 and k2 are constants representing the characteristics of the blower in the air handling system k3 and C are constants relating to the torque reduction rate above Smax with k3 = C/ASmax - k1, Slim is the speed limit, and Tmin is the minimum torque above the speed limit and is equal to - k3 ASlim + C.
10. The apparatus of claim 1, wherein the desired torque is defined by an algorithm which is a linear function of the speed and the desired rate of air flow, and wherein the linear function passes through the origin.
11. The apparatus of claim 10, wherein at least part of the algorithm defines the linear function as having a slope proportional to the desired air rate of air flow.
12. The apparatus of claim 1, wherein said microprocessor further comprises means for disabling operation of the motor in the event that the speed signal is not provided to the microprocessor.
13. The apparatus of claim 1, wherein said microprocessor comprises means for varying the torque of the motor in proportion to variations in motor speed, and in proportion to variations in the desired air flow rate signal.
14. The apparatus of claim 1, wherein said microprocessor operates in accordance with the following algorithm:
T=k1,AS, wherein T equals the desired torque of the motor A equals the desired rate of air flow S equal the motor speed and k, equals a constant representing the characteristics of the blower in the air handling system.
T=k1,AS, wherein T equals the desired torque of the motor A equals the desired rate of air flow S equal the motor speed and k, equals a constant representing the characteristics of the blower in the air handling system.
15. The apparatus of claim 1 wherein said microprocessor operates in accordance with the following algorithm:
T- TminforS~ Slim T = -k3 AS + C for Slim ~ S~ Smax T = k1, AS for Smax~ S~ (k2/k,) A and T=k2A2forS~(k2/k1)A, wherein T equals the desired torque of a motor, A equals the desired rate or air flow, S equals the motor speed, Smax equals the maximum operating speed at maximum torque, k1, and k2 are constants representing the characteristics of the blower in the air handling system, k3 and C are constants relating to the torque reduction rate above Smax with K3 = C/ASmax k1, Slim is the speed limit, and Tmin is the minimum torque above the speed limit and is equal to -k3ASlim + C.
T- TminforS~ Slim T = -k3 AS + C for Slim ~ S~ Smax T = k1, AS for Smax~ S~ (k2/k,) A and T=k2A2forS~(k2/k1)A, wherein T equals the desired torque of a motor, A equals the desired rate or air flow, S equals the motor speed, Smax equals the maximum operating speed at maximum torque, k1, and k2 are constants representing the characteristics of the blower in the air handling system, k3 and C are constants relating to the torque reduction rate above Smax with K3 = C/ASmax k1, Slim is the speed limit, and Tmin is the minimum torque above the speed limit and is equal to -k3ASlim + C.
16. The apparatus of claim 15, further comprising means for indicating the value of one or more of the constants to said microprocessor including an oscillator and means for varying the frequency of the oscillator as a function of the value of the constants.
17. The apparatus of claim 1, wherein the desired torque signal generated by said microprocessor is defined by a table specifying various values for the desired torque signal, each said value corresponding to a particular desired rate of air flow and a particular motor speed.
18. The apparatus of claim 1, further comprising means for indicating one or more preset desired rates of air flow to said microprocessor.
19. The apparatus of claim 18, wherein said means for indicating comprises an oscillator and means for varying the frequency of the oscillator as a function of the desired rate of air flow.
20. System for conditioning air and for maintaining a desired rate of air flow of the conditioned air through a contained space with respect to static pressure therein, the system comprising:
21 a motor having a stationary assembly with a plurality of winding stages for carrying motor current and further having a rotatable assembly in driving relation with a blower in the contained space;
means for generating a desired air flow rate signal which varies as a function of the desired rate of air flow;
means for providing a motor torque signal representative of the torque of the motor;
means for providing a speed signal representative of the speed of the motor;
a microprocessor, responsive to both the desired air flow rate signal and the speed signal, for generating a desired torque signal which is a function of both the desired air flow rate signal and the speed signal;
means for comparing the desired torque signal to the motor torque signal thereby to supply a comparison signal; and means for applying a motor voltage to one or more of the winding stages at a time in accordance with the comparison signal and for commutating the winding stages in a preselected sequence to rotate the rotatable assembly whereby the blower is driven by varying the motor torque according to motor speed to maintain air flow in the contained space at substantially the desired rate of air flow substantially independent of variations in the static pressure.
21. Method for controlling an air handling system including a motor having a stationary assembly with a plurality of winding stages for carrying motor current and further having a rotatable assembly in driving relation with a blower in the air handling system, the system further including means for generating a desired air flow rate signal which varies as a function of a desired rate of air flow, the method providing control of the blower speed over a range of static pressure variations to maintain
means for generating a desired air flow rate signal which varies as a function of the desired rate of air flow;
means for providing a motor torque signal representative of the torque of the motor;
means for providing a speed signal representative of the speed of the motor;
a microprocessor, responsive to both the desired air flow rate signal and the speed signal, for generating a desired torque signal which is a function of both the desired air flow rate signal and the speed signal;
means for comparing the desired torque signal to the motor torque signal thereby to supply a comparison signal; and means for applying a motor voltage to one or more of the winding stages at a time in accordance with the comparison signal and for commutating the winding stages in a preselected sequence to rotate the rotatable assembly whereby the blower is driven by varying the motor torque according to motor speed to maintain air flow in the contained space at substantially the desired rate of air flow substantially independent of variations in the static pressure.
21. Method for controlling an air handling system including a motor having a stationary assembly with a plurality of winding stages for carrying motor current and further having a rotatable assembly in driving relation with a blower in the air handling system, the system further including means for generating a desired air flow rate signal which varies as a function of a desired rate of air flow, the method providing control of the blower speed over a range of static pressure variations to maintain
22 the rate of air flow in the system at substantially the desired air flow rate, the method comprising the steps of:
sensing the torque of the motor;
sensing the speed of the motor;
determining, by use of a microprocessor which is responsive to both the desired air flow rate signal and the sensed motor speed, a desired torque which is a function of both the desired air flow rate and the sensed motor speed;
comparing the desired torque to the sensed motor torque;
applying a motor voltage to one or more of the winding stages at a time in accordance with the comparison; and commutating the winding stages in a preselected sequence to rotate the rotatable assembly whereby the blower is driven by varying the motor torque according to motor speed to maintain air flow in the system at substantially the desired rate of air flow substantially independent of variations in the static pressure.
22. The method of claim 21, wherein the torque of the motor is varied in proportion to variations in motor speed and in proportion to variations in the desired air flow rate signal.
sensing the torque of the motor;
sensing the speed of the motor;
determining, by use of a microprocessor which is responsive to both the desired air flow rate signal and the sensed motor speed, a desired torque which is a function of both the desired air flow rate and the sensed motor speed;
comparing the desired torque to the sensed motor torque;
applying a motor voltage to one or more of the winding stages at a time in accordance with the comparison; and commutating the winding stages in a preselected sequence to rotate the rotatable assembly whereby the blower is driven by varying the motor torque according to motor speed to maintain air flow in the system at substantially the desired rate of air flow substantially independent of variations in the static pressure.
22. The method of claim 21, wherein the torque of the motor is varied in proportion to variations in motor speed and in proportion to variations in the desired air flow rate signal.
23. The method of claim 22, wherein the torque of the motor is varied according to the following algorithm:
T = k1 AS
wherein T equals the desired torque of the motor, A equals the desired rate of air flow, S equals the motor speed and k1, equals a constant representing the characteristics a of the blower in the air handling system.
T = k1 AS
wherein T equals the desired torque of the motor, A equals the desired rate of air flow, S equals the motor speed and k1, equals a constant representing the characteristics a of the blower in the air handling system.
24. Apparatus for controlling a fluid handling system including a motor having a stationary assembly with a plurality of winding stages for carrying motor current and further having a rotatable assembly in driving relation with a fluid pump in the fluid handling system, the system further including means for generating a desired system parameter signal which varies as a function of a desired value for the parameter, the apparatus providing control of the fluid pump over various operating conditions of the fluid handling system to maintain the parameter at substantially the desired value, the apparatus comprising:
means for providing a motor torque signal representative of the torque of the motor;
means for providing a speed signal representative of the speed of the motor;
a microprocessor, responsive to both the desired parameter signal and the speed signal, for generating a desired torque signal which is a function of both the desired parameter signal and the speed signal;
means for comparing the desired torque signal to the motor torque signal and for supplying a comparison signal in response to the comparison; and means for applying a motor voltage to one or more of the winding stages at a time in accordance with the comparison signal and for commutating the winding stages in a preselected sequence to rotate the rotatable assembly whereby the fluid pump is driven by varying the motor torque according to motor speed to maintain the value of the parameter at substantially the desired value substantially independent of variations in the operating conditions of the fluid handling system.
means for providing a motor torque signal representative of the torque of the motor;
means for providing a speed signal representative of the speed of the motor;
a microprocessor, responsive to both the desired parameter signal and the speed signal, for generating a desired torque signal which is a function of both the desired parameter signal and the speed signal;
means for comparing the desired torque signal to the motor torque signal and for supplying a comparison signal in response to the comparison; and means for applying a motor voltage to one or more of the winding stages at a time in accordance with the comparison signal and for commutating the winding stages in a preselected sequence to rotate the rotatable assembly whereby the fluid pump is driven by varying the motor torque according to motor speed to maintain the value of the parameter at substantially the desired value substantially independent of variations in the operating conditions of the fluid handling system.
25. Apparatus for controlling a fluid handling system including a motor having a stationary assembly with a plurality of winding stages for carrying motor current and further having a rotatable assembly in driving relation with a fluid pump in the fluid handling system, the system further including means for generating a desired system parameter signal which varies as a function of a desired value for the parameter, and means for generating a motor current signal representative of the motor current, the apparatus providing control of the fluid pump over a range of various operating conditions of the fluid handling system to maintain the parameter at substantially the desired value, the apparatus comprising:
means for providing a speed signal representative of the speed of the motor;
a microprocessor to both the desired parameter signal and the speed signal, for generating a desired current signal which is a function of both the desired parameter signal and the speed signal means for comparing the desired current signal to the motor current signal and for supplying a comparison signal in response to the comparison; and means for applying a motor voltage to one or more of the winding stages at a time in accordance with the comparison signal and for commutating the winding stages in a preselected sequence to rotate the rotatable assembly whereby the fluid pump is driven to maintain the value of the parameter at substantially the desired value substantially independent of variations in the operating conditions of the fluid handling system.
means for providing a speed signal representative of the speed of the motor;
a microprocessor to both the desired parameter signal and the speed signal, for generating a desired current signal which is a function of both the desired parameter signal and the speed signal means for comparing the desired current signal to the motor current signal and for supplying a comparison signal in response to the comparison; and means for applying a motor voltage to one or more of the winding stages at a time in accordance with the comparison signal and for commutating the winding stages in a preselected sequence to rotate the rotatable assembly whereby the fluid pump is driven to maintain the value of the parameter at substantially the desired value substantially independent of variations in the operating conditions of the fluid handling system.
26. System for conditioning fluid and for maintaining as substantially constant a desired parameter of the conditioned fluid through a contained space with respect to variations in operating conditions of the contained space the system comprising:
a motor having a stationary assembly with a plurality of winding stages for carrying motor current and further having a rotatable assembly in driving relation with a fluid pump in the contained space;
means for generating a desired system parameter signal which varies as a function of a desired value or the parameter;
means for providing a motor torque signal representative of the torque of the motor;
means for providing a speed signal representative of the speed of the motor;
a microprocessor, responsive to both a desired parameter signal and the speed signal, for generating a desired torque signal which is a function of both the desired parameter signal and the speed signal;
means for comparing the desired torque signal to the motor torque signal thereby to supply a comparison signal; and means for applying a motor voltage to one or more of the winding stages at a time in accordance with the comparison signal and for commutating the winding stages in a preselected sequence to rotate the rotatable assembly whereby the fluid pump is driven by varying the motor torque according to motor speed to maintain the value of the parameter at substantially the desired value substantially independent of variations in the operating conditions of the contained space.
a motor having a stationary assembly with a plurality of winding stages for carrying motor current and further having a rotatable assembly in driving relation with a fluid pump in the contained space;
means for generating a desired system parameter signal which varies as a function of a desired value or the parameter;
means for providing a motor torque signal representative of the torque of the motor;
means for providing a speed signal representative of the speed of the motor;
a microprocessor, responsive to both a desired parameter signal and the speed signal, for generating a desired torque signal which is a function of both the desired parameter signal and the speed signal;
means for comparing the desired torque signal to the motor torque signal thereby to supply a comparison signal; and means for applying a motor voltage to one or more of the winding stages at a time in accordance with the comparison signal and for commutating the winding stages in a preselected sequence to rotate the rotatable assembly whereby the fluid pump is driven by varying the motor torque according to motor speed to maintain the value of the parameter at substantially the desired value substantially independent of variations in the operating conditions of the contained space.
27. Method for controlling an air handling system including a motor having a stationary assembly with a plurality of winding stages for carrying motor current and further having a rotatable assembly in driving relation with a fluid pump in a fluid handling system, the system further including means for generating a desired system parameter signal which varies as a function of a desired value for the parameter, the method providing control of the fluid pump over variations in the operating conditions of the fluid handling system to maintain the parameter at substantially the desired value, the method comprising the steps of:
sensing the torque of the motor, sensing the speed of the motor;
determining, by use of a microprocessor which is responsive to both the desired system parameter signal and the sensed motor speed, a desired torque which is a function of both the desired system parameter signal and the sensed motor speed;
comparing the desired torque to the sensed motor torque, applying a motor voltage to one or more of the winding stages at a time in accordance with the comparison, and commutating the winding stages in a preselected sequence to rotate the rotatable assembly whereby the fluid pump is driven by varying the motor torque according to the motor speed to maintain the value of the parameter at substantially the desired value substantially independent of variations in the operating conditions of the fluid handling system.
sensing the torque of the motor, sensing the speed of the motor;
determining, by use of a microprocessor which is responsive to both the desired system parameter signal and the sensed motor speed, a desired torque which is a function of both the desired system parameter signal and the sensed motor speed;
comparing the desired torque to the sensed motor torque, applying a motor voltage to one or more of the winding stages at a time in accordance with the comparison, and commutating the winding stages in a preselected sequence to rotate the rotatable assembly whereby the fluid pump is driven by varying the motor torque according to the motor speed to maintain the value of the parameter at substantially the desired value substantially independent of variations in the operating conditions of the fluid handling system.
28. Apparatus for controlling an air handling system including a motor having a stationary assembly with a plurality of winding stages for carrying motor current and further having a rotatable assembly in driving relation with a blower in the air handling system, the system further including means for generating a desired air flow rate signal which varies as a function of a desired rate of air flow and means for generating a motor current signal representative of the motor current, the apparatus providing control of the blower speed over a range of static pressure variations to maintain the rate of air flow in the system at substantially the desired air flow rate, the apparatus comprising;
means for providing a speed signal representative of the speed of the motor;
a microprocessor, responsive to both the desired air flow rate signal and the speed signal, for generating a desired current signal which is a function of both the desired air flow rate signal and the speed signal;
means for comparing the desired current signal to the motor current signal for supplying a comparison signal in response to the comparison, and means for applying a motor voltage to one or more of the winding stages at a time in accordance with the comparison signal and for commutating the winding stages in a preselected sequence to rotate the rotatable assembly whereby the blower is driven to maintain air flow in the system at substantially the desired rate of air flow substantially independent of variations in the static pressure.
means for providing a speed signal representative of the speed of the motor;
a microprocessor, responsive to both the desired air flow rate signal and the speed signal, for generating a desired current signal which is a function of both the desired air flow rate signal and the speed signal;
means for comparing the desired current signal to the motor current signal for supplying a comparison signal in response to the comparison, and means for applying a motor voltage to one or more of the winding stages at a time in accordance with the comparison signal and for commutating the winding stages in a preselected sequence to rotate the rotatable assembly whereby the blower is driven to maintain air flow in the system at substantially the desired rate of air flow substantially independent of variations in the static pressure.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US385,664 | 1989-07-26 | ||
| US07/385,664 US4978896A (en) | 1989-07-26 | 1989-07-26 | Method and apparatus for controlling a blower motor in an air handling system |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2015509A1 CA2015509A1 (en) | 1991-01-26 |
| CA2015509C true CA2015509C (en) | 1998-06-23 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002015509A Expired - Lifetime CA2015509C (en) | 1989-07-26 | 1990-04-26 | Method and apparatus for controlling a blower motor in an air handling system |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US4978896A (en) |
| CA (1) | CA2015509C (en) |
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| JPS58107022A (en) * | 1981-12-21 | 1983-06-25 | 日本ビクター株式会社 | Circuit for protecting motor |
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| US4806833A (en) * | 1986-09-22 | 1989-02-21 | General Electric Company | System for conditioning air, method of operating such, and circuit |
| US4818924A (en) * | 1987-07-31 | 1989-04-04 | A.R.A. Manufacturing Co. | Electric actuator for automotive air conditioning systems |
| US4858676A (en) * | 1988-10-05 | 1989-08-22 | Ford Motor Company | Airconditioning system for a vehicle |
-
1989
- 1989-07-26 US US07/385,664 patent/US4978896A/en not_active Expired - Fee Related
-
1990
- 1990-04-26 CA CA002015509A patent/CA2015509C/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| US4978896A (en) | 1990-12-18 |
| CA2015509A1 (en) | 1991-01-26 |
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