US2814016A - Electric metering devices - Google Patents

Description

NOV. 19, D. J. WARD v ELECTRIC METERING DEVICES Original Filed Nov. 13, 1945 f 2 Sheets-Sheet 1 INVENTOR! Delberf J. Ward v AGENT Nov. 19, 1957 D. J. WARD 2,814,016

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INVENTOR. De/ber? Wqfc/ AGE/VT United States Patent ELECTRIC METERING DEVICES Delbert J. Ward, Los Angeles, Calif.

Original application November 13, 1945, Serial No. 628,194, now Patent No. 2,600,088, dated June 10, 1952. Divided and this application June 9, 1952, Serial No. 292,431

Claims. (Cl. 323-75) This invention pertains to galvanometers and galvanometer circuits, and the instant application is a division of my earlier application Serial Number 628,194, filed November 13, 1945, now Patent No. 2,600,088, covering certain instrumentation networks.

One object of my invention is to provide an electronic polarized alternating current galvanometer.

A further object is to make the responses of such a galvanometer independent of the frequency of the current.

Another object is to provide means whereby equal increments near a zero center galvanometer scale will indicate relatively small current variations and equal increments more remote from the zero center will indicate relatively large current variations.

In the drawings:

Fig. 1 is a diagram of an instrumentation network comprising my galvanometer and circuit arrangements.

Fig. 2 shows a modification of a portion of the circuits shown in Fig. 1.

Fig. 3 is a diagram of another instrumentation network embodying my invention.

Fig. 4 is a diagram of an alternative circuit arrangement.

My invention will be best understood if it is explained in connection with an instrumentation network of a type in which it has been successfully used. Fig. 1 shows such a network, this figure being the same as Fig. 7 of my earlier application Serial Number 628,194, of which the present application is a division. work is useful for comparing impedances and for diagnosing winding defects in the armatures of motors and generators. I obtain the voltages to operate the system from a 4000 cycle oscillator and power amplifier having a conventional power supply. This alternating current source 83 is indicated in the left portion of the figure. Conductors 81 and 82 are connected to this current source. Resistors R2, R3 and R4 are connected in series across these conductors in the manner shown, R3 being a variable resistor or potentiometer having a slider 84 which may be adjusted for zero potential in a manner later to be described. These three resistors form one arm of an alternating current bridge. The three pole, double-throw switch S2 is used for connecting into the circuit the impedances that are to form the second arm of the bridge. Blades 86 and 88 are respectively connected to conductors $1 and 82 by wires 85 and 87 respectively. When these blades are on the upper contacts 89 and 90, connection is made to wires 92 and 93 which are shown leading to power brushes 34 and 35, or a motor analyzing device, which may be of the type described in my application Serial Number 292,430, now Patent No. 2,704,824, filed herewith. The coils on the This particular net- 2,814,016 Ce Patented Nov. 19, 1957 two sides of the armature 91 (that is, on opposite sides of the power brushes) are in parallel. Otherwise stated, inductance Z1 and Z2 are in parallel with inductance Z4. These impedances, connected across conductors 81 and 82 by switch S2, form the second arm of the bridge.

When the three-pole double-throw switch S2 is in the position described, the center blade 94 will be on pole 95, thus connecting brush 47 and wire 96 to conductor 97. When switch S1 is closed, the balance arm of the bridge then consists of brush 47, conductor 96, blade 94, conductor 97, switch S1, conductor 99, the primary of transformer T1, and conductors 100, 101 and 102, the latter connecting to the wiper 84 of the variable resistor R3. When the impedances Z1 and Z2 are equal respectively to the impedance offered by the resistances in the first arm on opposite sides of the wiper 84, there will of course be no current in the balance arm of the bridge and transformer T1 will not be energized. If the impedances in the second arm of the bridge do not balance the corresponding impedances in the first arm, current will flow in one direction or other through the balance arm. The resulting current in the primary of transformer T1 will produce a voltage in the secondary, thus placing opposite potentials on the control elements of electronic amplifying devices V1 and V2. These two devices rectify the current in two circuits connected in parallel across the main conductors 81 and 82. The first circuit includes the electronic amplifying device V1, a filter which comprises choke T3 and condenser C3, and the resistors R7 and R8; and the second circuit includes electronic amplifying device V2, the filter consisting of choke T4 and condenser C4, and the resistors R10 and R11. These circuits might be considered the first and second arms of a second bridge.

Because of the high inductance of the chokes T3 and T4, very little current flows through them. I therefore connect diode V4 from conductor 82 to a point between choke T3 and the electronic amplifying device V1, these valves being arranged so that their directions of conductivity are opposed. As a result, the energy stored in choke T3 passes through diode V4 during the halfcycle when electronic amplifying device V1 is non-conductive. This current reaches point 103 through resistor R8. In the second arm of the second bridge, diode V6 is connected across choke T4 and condenser C4, the connection on one side being made direct to the main conductor 82. This diode is conductive on the half cycle when the electronic amplifying device V2 is non-conductive, and, like diode V4, it permits the energy in its associated choke to be discharged around the choke and through resistor R11 and part of resistor R10 to slider 123. Diodes, rather than condensers, are employed to bypass these chokes, because we are dealing with an integration of the entire half cycle wave instead of merely with the peak, as would be the case if condensers were used instead of valves.

Resistor R9, the zero-center D. C. galvanometer M, and resistor R12 form the balance arm of this second bridge, and slider 123 is adjusted so that there is no current in either direction through the meter when transformer T1 is not energized that is, when there is no current through the balance arm of the first bridge. Resistor R12 is variable to provide a compensation adjustment for the A. C. voltage applied to the network, and permits the meter M to function properly irrespective of the applied voltage. Resistor R12 is shunted by condenser 124 to eliminate spurious A. C. pickup in the wiring of the various components. The use of diodes V4 and V6, rather than condensers, enables the galvanometer M to respond to a condition more nearly approaching the average voltage of the half cycle than would be the case if condensers were employed.

The remainder of the network will be better understood if we first explain the functioning of the circuits and components already mentioned. Let us suppose that we throw the three-pole, double-throw switch so that blades 36, 94 and 88 respectively engage contacts 125, 126 and 127, and that these contacts have been connected to impedances Z1 and Z2 whose values are to be con pared. These impedances now form the second arm of the first bridge previously described, and the balance arm consists of conductor 128, contact 126, blade conductors 97 and 98, switch S1, conductor 99, the primary or" transformer T1, and conductors ltltl, llll and 1&2. if the voltage drop across each of the impedances Z1 and Z2 is equal respectively to the voltage drop across resis tors R2 and R4, there will of course be no current through transformer T1 and the control elements of the electronic amplifying devices V1 and V2 will have the same potential; but if impedance Z1 and Z2 are not of equal value, the phase of the current flowing through the primary of transformer T1 will depend upon which impedance is the greater. The control elements of the electronic amplifying devices will thus have opposite potentials whose differences will vary with the extent of variation in the values of the impedances Z1 and Z2. This will result in the presence of unequal D. C. voltages on condensers C3 and C4 and at point 103 and wiper 123, the relative polarity of which will be indicated on meter M in the balance arm of the second bridge.

If either impedance Z1 and Z2 is very much greater than the other, or if a short occurs across one of the two elements in this second arm of the first bridge, the resulting difference of potential on the control elements of the electronic amplifying devices might be great enough to produce a sufiiciently excessive current through the meter M to injure the meter movement. Biased diodes V5 and V7, connected in reverse parallel across the meter and resistor 9, provide a means for preventing such injur, and also afford a means whereby a given angular movement of the galvanometer needle near the zero center of the galvanometer scale will represent a smaller current variation than the same angular movement near the outer ends of the scale. Diodes V5 and V7 are biased respectively by batteries 129 and 13%, either or both of which could equally well be placed on the opposite side of the associated diode. When the IR drop through the resistor R9 and the meter M exceeds the algebraic sum of the bias voltage and the cathode emission voltage of the diode V5 or V7, whichever is of correct polarity, a portion of the current flowing through resistor R12 is bypassed around the meter, thereby changing its sensitivity as an indicator of the total current flowing through this resistor. The bias voltages may be adjusted so that the sensitivity changes at any desired point. In the first model built, this was adjusted so that 50% of the scale on either side of zero represented a 15% unbalance in the impedances under test, while the remaining 85% of a 100% unbalance was represented by the remainder of the two sides of the scale. The biased diodes thus conduct a small amount of a weak current but carry the greater portion of a strong current.

Diodes V4 and V7 are encased in the same en elope and diodes V5 and V5 in another. The reason for this will be apparent if we examine the situation that would prevail if the filament for diode V4 or V6 should burn out. Should the filament for diode V4, for example, burn out, the current through the circuit of which it is a part would be very materially reduced, because the action of choke T3 would permit very little current to pass through. This would unbalance the bridge, resulting in sufficient current through resistor R12 to injure the movement of galvanometer M if the biased valve V5 were not there to protect it. Since both the diodes that are in the same envelope have a common filament, serious injury to the galvanorneter would thus occur if diode V5 had the same filament as diode V4. If diodes V4 and V7, however, are in the same envelope, no harmful situation can arise, because the loss of their common filament makes diode V4 non-conductive, thus making the potential so low at point 103 that no current would flow through the galvanorneter system in the direction in which diode V7 is conductive. if the diodes were in individual envelopes, the loss of either diodes V5 or V7 would leave the galvanometer with out protection from excessive currents in one direction, but when each of these diodes is paired in a common envelope with the diode through which such excessive current would have to pass, the simultaneous loss of both diodes avoids the excessive currents to which the biased diode of the pair would ordinarily respond.

A calibrating network, shown at the extreme ight of Fig. l, is provided to facilitate the determination of the alternating current midpotential at point res and at the slider 123. A plus and minus 10% unbalance top is also provided to check the calibration of the special scale associated with galvanometer M. This calibrating network is controlled by a three-pole, five-way switch S3. When the blades of this switch are on the taps located furthest to the left, the calibrating network is entirely out of the circuit.

The center blade or wiper 133 of switch S3 is con nected to conductor 134 which makes connection with one end of the balance arm of the alternating current bridge through conductors 97 and 98 and switch S1. When switch S3 is turned to its second position from the left, blade 133 engages contact 135, thus making electrical connection with conductor 136 which connects with the opposite end of the balance arm, thus shorting the primary of transformer T1. This removes the possibility of there being any unequal currents through the triodes and permits the galvanometer M to be adjusted to zero position with respect to the D. C. bridge network in the full assurance that no current is passing through it.

When switch S3 is in its central position while the blades of switch S2 are out of engagement with their respective contacts, it will be clear that resistors R16, R17, R18 and R19 are connected to form the second arm of the alternating current bridge across conductors 81 and 82. The resistors R16 and R17 of course form one element of the arm and resistors R18 and R19 the other. The connection that switch S3 thus makes, enables the adjustment of wiper 84 to be checked for the A. C. midpotential.

When the switch S3 is in its fourth position from the left, resistor R16 will be alone on one side of the balance arm, and the impedance of resistor R17 will he added to the other side. The value of resistor R17 is such that this shift creates a 10% unbalance in one direction, thus enabling the operator to check the calibration of the dial of galvanometer M. When switch S4 is in its fifth position from the left, which is also the extreme position to the right, resistor R19 will be alone on one side of the balance arm and the impedance of resistor R18 wil he added to the side opposite that on which it normally belongs. This creates a 10% unbalance in the dir ction opposite from that created when the switch is in its rth position, and the calibration of the galvanorneter dial may thus be checked on the side opposite the one previously checked.

An explanation of Fig. 2, which shows modifications applicable to the network of Fig. 1, requires that we examine certain phases of the operation of the said network. When the potentials on the control elements of electronic amplifying devices V1 and V2 (Fig. 1) are equal, due to an absence of current through transformer T1, it will readily be understood that an increase of voltage across conductors 81 and 82 will result in an equal increase of current through the two said devices. In such a situation, the increase in supply voltage will therefore not unbalance the direct current bridge that includes the galvanometer M. But if there is an imbalance in the coils being tested, the resulting current through transformer T1 will place unequal potentials on the control elements of devices V1 and V2, and although these unequal control potentials will of course not change in relative values when the supply voltage is increased, they will produce a greater variation in the current flowing through the two said devices at the increased voltage than at the lower. For a given percentage imbalance through the balance arm that includes the primary of transformer T1, there will thus be a greater current through the galvanometer M with a high supply voltage than with a low supply voltage. In the network as shown in Fig. 1, resistor R12 is made variable to compensate for the eifects of such changes in the supply voltage. Fig. 2 shows an arrangement whereby these changes are automatically compensated for. This diagram shows the metering or balance arm of the second bridge-that is, the direct current bridgeand points 103 and slider 123 are those having the corresponding numbers in Fig. 1. In following the explanation of this circuit, is it to be remembered that all parts of the network may be identical to those shown in Fig. 1 excepting for the changes shown in Fig. 2. The primary of transformer T5 is connected across the conductors 81 and 82 carrying the A. C. voltage supply. An increase in this voltage increases the voltages in the secondaries of this transformer, producing a correspondingly increased negative potential on the control elements of electronic amplifying devices V8 and V9. This in turn increases the resistance through these devices to compensate for the increase in supply voltage. When the current in the balance arm between point 103 and slider 123 is in one direction, it is conducted through one of the said devices, and when it is in the opposite direction, it is conducted through the other. The four condensers shown assist in filtering.

Fig. 3 shows a modified network for accomplishing the same over-all polarized indication achieved by the network of Fig. 1. In this system, the ground insulation is indicated directly on the ohmmeter M2a. balance arm is substantially the same as in the circuit of Fig. l, the primary of transformer T1 being connected from the balance brush 42 to the A. C. midpoint 84, which is at the same potential as the cathode and plate respectively of the rectifying diodes Vla and V2a. When there is no imbalance current in the transformer T1, any current that may be flowing through diodes V4a and V541 and their associated resistors will be equal; but when the primary of T1 impresses an imbalance current on the secondary, then the potentials on the plates of valves V4a and V5a will change in accordance with the direction of the imbalance current, and the current through these valves will also change accordingly. The cathodes of these tubes will have potentials that vary according to the respective voltages applied to the plates of these tubes and the direction and amount of deflection of the indicator of galvanometer Mla will correspond to the relative values of these potentials, thus giving an indication ofthe imbalance of the two impedances under test.

Fig. 4 shows another modified network embodying my invention and achieving the same over-all result as the networks of Figs. 1 and 3. In this circuit, the primary of transformer T1 that carries the imbalance current is coupled inductively to two secondaries 141 and 142, to which the control elements of the electronic amplifying devices V3a and Ma are connected. When there is no current in either direction through the primary of transformer T1, there is no difference of potential on these control elements, but when transformer T1 is energized by an imbalance current, the control potentials The A. C. 4

change according to the direction and degree of imbal: ance. The resulting change in resistance through electronic amplifying devices V3a and V4a changes the D. C. mid potential at point 143, and current flows through the galvanometer Mlb in accordance with the direction and strength of the imbalance current, thus giving a visual indication on the scale of the imbalance of the impedances under test.

It will readily be understood that various substitutions, omissions, additions and rearrangements of the elements of my invention may be made without departing from its broad spirit and fundamental concept as set forth in the appended claims.

My claims are:

l. A device for producing a direct current voltage the polarity and magnitude of which is controlled by the relative polarity and relative magnitude of the voltages in two alternating current systems, said device comprising: first and second conductors connected to a first alternating current source; first and second branches of a Wheatstone type bridge connected across said conductors, each of said branches of said bridge comprising a first arm including an electronic amplifying device having at least three elements and :a filtering system connected to one of the output elements of said amplifying device, and a second arm comprising an impedance; means responsive to a voltage from a second alternating current source for impressing opposite voltages upon the control elements of said electronic amplifying devices to render the first :arms of the two branches of said bridge unequally oonductive, thereby producing a direct current voltage differential between a point intermediate the arms of one branch of said bridge and the conjugate point of the other branch of said bridge, to indicate the magnitude and direction of said voltage from said second alternating current source.

2. A device for producing a direct current voltage the polarity and magnitude of which is controlled by the relative polarity and relative magnitude of the voltages in two alternating current systems, said device comprising: first .and second conductor-s connected to a first alternating current source; first and second branches of a Wheatst'one type bridge connected across said conductors, each of said branches of said bridge comprising a first arm including an electronic amplifying device having at least three elements and a filtering :system connected to tone of the output elements of said amplifying device, and a second arm comprising a resistor; means responsive to a voltage from a second alternating current source for impressing opposite voltages upon the control members of said electronic amplifying devices to render the first arms of the two branches :of said bridge unequally conductive, thereby producing a direct current voltage differential between a point intermediate the arms of one branch of said bridge and the conjugate point of the other branch of said bridge, to indicate the magnitude and direction of said voltage from said second alternating current source.

3. A device for producing a direct current voltage the polarity and magnitude of which is controlled by the relative polarity and relative magnitude of the voltages in two alternating current systems, said device comprising: first and second conductors connected to a first alternating current source; first and second branches of a Wheatstone type bridge connected across said conductors, each of said branches of said bridge comprising 1) a first arm including (a) an electronic amplifying device having at least three elements and (b) a filtering system that comprises an impedance and a rectifier that is so arranged with respect to the associated electronic amplifying device that the energy stored in the impedance will pass through the rectifier during the half cycle when the electronic amplifying device is non-conductive, and (2) a second arm comprising a resistor; means responsive to a voltage from a second alternating current source for impressing opposite voltages upon the control elem'ents of said electronic amplifying devices to render the first arms of the two branches of said bridge unequally conductive, thereby producing a direct current voltage differential between a point intermediate the arms of one branch of said bridge and the conjugate point of the other branch of said bridge, to indicate the magnitude and direction of said voltage from said second alternating current source.

4. A device for producing a direct current voltage the polarity and magnitude of which is controlled by the relative polarity and relative magnitude of the voltages in two alternating current systems, said device comprising: first and second conductors connected to a first alternating current source; first and second branches of a Wheatstone type bridge connected across said conductors, each of said branches of said bridge comprising a first arm, including an electronic amplifying device having at least three element, and a second arm comprising an impedance connected to one of the output elements of said amplifying device; means responsive to a voltage from a second alternating current source for impressing opposite voltages upon the control elements of said electronic amplifying devices to render the first arms of the two branches of said bridge unequally conductive, thereby producing a direct current voltage differential between a point intermediate the arms of one branch of said bridge and the conjugate point of the other branch of said bridge, to indicate the magnitude and direction of said voltage from said second alternating current source.

5. A device for producing a direct current voltage the polarity and magnitude of which is controlled by the relative polarity and relative magnitude of the voltages in two alternating current systems, said device comprising: first and second conductors connected to a first alternating current source; first and second branches of a Wheatstone type bridge connected across said conductors, each of said branches of said bridge comprising a first arm including an electronic amplifying device having at least three elements and a second arm comprising an impedance connected to one of the output elements of said amplifying device; means responsive to a voltage from a second alternating current source for impressing opposite voltages upon the control members of said electronic amplifying devices to render the first arms of the two branches of said bridge unequally conductive, thereby producing a direct current voltage differential between a point intermediate the arms of one branch of said bridge and the conjugate point of the other branch of said bridge, to indicate the magnitude and direction of said voltage from said second alternating current source.

6. A device for producing a direct current voltage the polarity and magnitude of which is controlled by the relative polarity and relative magnitude of the voltages in two alternating current systems, said device comprising: first and second conductors connected to a first alternating current source; first and second branches of a Wheatstone type bridge connected across said conductors, each of said branches of said bridge comprising: a first arm including an electronic amplifying device having at least three elements and a filtering system connected to one of the output elements of said amplifying device, and a second arm comprising a resistor; a transformer having its primary connected to a second alternating current source and each end of its secondary connected to the control element of a different one of said electronic amplifying devices for impressing opposite voltages upon the control elements of said electronic amplifying devices to render the first arms of the two branches of said bridge unequally conductive, thereby producing a direct current voltage differential between a point intermediate the arms of one branch of said bridge and the conjugate point of the other branch of said bridge, to indicate the magnitude and direction of said voltage from said second alternating current source.

7. A device for producing a direct current voltage the polarity and magnitude of which is controlled by the relative polarity and relative magnitude of the voltages in two alternating current systems, said device comprising: first and second conductors connected to a first alternating current source; first and second branches of a Wheatstone type bridge connected across said conductors, each of said branches of said bridge comprising a first arm including an electronic amplifying device having at least three elements, and a second arm comprising an impedance connected to one of the output elements of said amplifying device; means responsive to a voltage from a second alternating current source for impressing opposite voltages upon the control elements of said electronic amplifying devices to render the first arms of the two branches of said bridge unequally conductive, thereby producing a direct current voltage differential between a point intermediate the arms of one branch of said bridge and the conjugate point of the other branch of said bridge to indicate the magnitude and direction of said voltage from said second alternating current source.

8. A device for producing a direct current voltage the polarity and magnitude of which is controlled by the relative polarity and relative magnitude of the voltages in two alternating current systems, said device comprising: first and second conductors connected to a first alternating current source; first and second branches of a Wheatstone type bridge connected across said conductors, each of said branches of said bridge comprising a first arm inclucling an electronic amplifying device having at least three elements, and a second arm comprising a resistor connected to one of the output elements of said amplifying device; means responsive to a voltage from a second alternating current source for impressing opposite voltages upon the control members of said electronic amplifying devices to render the first arms of the two branches of said bridge unequally conductive, thereby producing a direct current voltage differential between a point intermediate the arms of one branch of said bridge and the conjugate point of the other branch of said bridge to indicate the magnitude and direction of said voltage from said second alternating current source.

9. A device for producing a direct current voltage the polarity and magnitude of which is controlled by the relative polarity and relative magnitude of the voltages in two alternating current systems, said device comprising: first and second conductors connected to a first alternating current source; first and second branches of 21 Wheatstone type bridge connected across said conductors, each of said branches of said bridge comprising (1) a first arm including an electronic amplifying device having at least three elements, and (2) a second arm comprising a resistor connected to one of the output elements of said amplifying device; means responsive to a voltage from a second alternating current source for impressing opposite voltages upon the control elements of said electronic amplifying devices to render the first arms of the two branches of said bridge unequally conductive, thereby producing a direct current voltage differential between a point intermediate the arms of one branch of said bridge and the conjugate point of the other branch of said bridge to indicate the magnitude and direction of said voltage from said second alternating current source.

10. A device for producing a direct current voltage the polarity and magnitude of which is controlled by the relative polarity and relative magnitude of the Voltage in two alternating current systems, said device comprising: first and second conductors connected to a first alternating current source; first and second branches of a Wheatstone type bridge connected across said conductors, each of said branches of said bridge comprising a first arm including an electronic amplifying device having at least three elements, and a second arm comprising a resistor connected to one of the output elements of said amplifying device; a transformer having its primary connected to a second alternating current source and each end of 2,814,016 A 9 10 c its secondary connected to the control element of a dif- References Cited in the file of this patent ferent one of said electronic amplifying devices for impressing opposite voltages upon the control elements of UNITED STATES PATENTS said electronic amplifying devices to render the first arms 1,822,996 Mirick Sept. 15, 1931 of the two branches of said bridge unequally conductive, 5 1,893,780 Lyman Jan. 10, 1933 thereby producing a direct current voltage differential be- 2,318,140 Clark May 4, 1943 tween a point intermediate the arms of one branch of said 2,450,930 Baclawski Oct. 12, 1948 bridge and the conjugate point of the other branch of said 2,490,167 Storm Dec. 6, 1949 bridge to indicate the magnitude and direction of said 2,569,949 Prescott Oct. 2, 1951 voltage from said second alternating current source. 10 2,588,292 Rittner et a1 Mar. 4, 1952

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