US2677075A - Apparatus for operating electric discharge devices - Google Patents

Description

P 27, 1954 J. H. CAMPBELIL ETAL 2,577,075

APPARATUS FOR OPERATING ELECTRIC DISCHARGE DEVICES Filed Dec. 8, 1951 3 Sheets-Sheet l OPEN CIRCUIT LAMP 1 STARTED NORMAL OPERATION Inventors: John H. Campbell Delmar- D. Kershaw Their Attorney April 1954 J. H. CAMPBEL ETAL 2,

APPARATUS FOR OPERATING mzc'mxc DISCHARGE msvxcss Filed D60. 8 1951 3 Sheets-Sheet 2 16 I6 N Fig. 26.

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a. 24 P 23 I2 5 P a s OPEN CIRCUIT Fig. 2c

LAMP 1 STAR TED 17. 2d I 9 NORMAL ORERATION 1 nve nt 0 r s:

John H. Campbell Delmar" D. Ke-rshaw b wc: 44%.

Their Attorney April 27, 1954 J. H. CAMPBELL ETAL 2,677,075

APPARATUS FOR OPERATING ELECTRIC DISCHARGE DEVICES Filed Dec. 8, 1951 3 Sheets-Sheet 3 A\ fiif e 26 e 30 6 2 T l I' I I 29 2 0,; 2 a n, 2 a! Fig 3b e a. s OPEN CIRCUIT LAMP 1 STARTED NORMAL OPERATION Inventors: ca John H CampbeH Del ar D. Kershaw Their" Attorn'ey Patented Apr. 27, 1954 UlTED STAT rem-1r o-FFicE.

APPARATUS FOR OPERATING ELECTRIC DISCHARGE DEVICES York Application December 8, 1951, Serial No. 260,694

'7 Claims.

This invention relates to apparatus for starting and controlling gaseous electric discharge devices such as fluorescent lamps, and more particularly to circuits suitable for instant start lamps, that is, lamps wherein the discharge is initiated by the application of an instantaneous high voltage and wherein the electrodes are not preheated at starting.

The invention is concerned with a starting and operating apparatus of the type commonly known as a sequence-start series ballast wherein two lamps are operated in series after starting in sequence. Such apparatus generally comprises a transformer or auto-transformer having a primary winding and a high leakage reactance secondary winding, both windings having a current carrying capacity at least sufficient for the normal operating current of the lamps. In addition, there is provided some means, such as an auxiliary winding of relatively low current carrying capacity, which is connected to assist in starting the lamps. After one lamp has been started, the reduced voltage drop across it permits starting of' the second lamp without difficulty.

With the present sequence-start series type of ballast, the difficulty has been encountered that the auxiliary winding, when it is designed to have a current carrying capacity suflicient for its starting function only, often burns out when one of the lamps approaches the end of its life. Such burning out appears to be due to the fact rat one of the cathodes in a lamp generally becomes deactivated before the other. When this condition prevails, the lamp tends to operate as a half-wave rectifier, resulting in a flow of unidirectional current through the auxiliary winding with consequent saturation of its core, reduction of its reactance, and increase in current. In order to avoid overheating under these conditions, it has been found necessary to construct the auxiliary winding with a much higher current carrying capacity than is necessary for its normal function. I

An object or the present invention is to provide a new and improved sequence-start series type ballast for discharge devices which avoids the above-described difficulties.

Another object of the invention is to provide improved sequence-start series circuits for discharge lamps which lend themselves particularly well to disconnecting the primary winding from thesupply circuit by the removal of either lamp from its connectors or lampholders.

In accordance with our invention, the operat' ing circuit comprises a high leakage reactance transformer whose main function is to provide operating voltage and at the same time to regulate the current in a pair of series connected lamp-s. transformer an auxiliary or extended winding of relatively low current carrying capacity. The current capacity of this winding need be merely equal to the current required to establish hot spots on the electrodes of-the lamps in order to reduce the voltage drop across the arc discharge to a value close to the operating value. In view or its extremely low current capacity, the auxilary winding adds comparatively little to the cost of manufacture of the transformer, and, when connected in accordance-with our improved circuit, it permits a very considerable reduction in the open circuit voltage required of the secondary winding. The secondary winding naturally must have a comparatively large current carrying capacity, at least suilicient to provide the rated current to the lamps, so that it is economically advantageous to add the auxiliary winding in view of the reduction insiz of the main winding which it permits.

For further objects and advantages and for a better understanding of our invention, attention is now directed to the following description and to the accompanying drawings. The features of our invention believed to be novel will be more particularly pointed out in the appended claims.

In the drawings, wherein like reference numerals denote corresponding elements:

Fig. La. is a schematic. diagram of the basic circuit of our invention and Figs. 1b to 1d. are vector diagrams relatingthereto.

Figs. 2a and 3a are schematic diagrams of modified circuits embodying our invention wherein provision is made for disconnecting. the primary winding when either lamp is removed from its socket. Figs. 2b-to 2d and Figs. 3b to Bdare the corresponding vector diagrams.

Referring to Fig. 1a, there is shown a pair of long tubular electric. discharge devices DI and D2, which may for example be '75 watt fiuorese cent lamps 8 feetin length and 1%? inches in diameter. Each lamp is provided with a pair of activated filamentary electrodes l, l enclosed in elongated envelopes. containing mercury vapor at a low pressure and a suitable starting gas such as argon. The lead-in wires of each electrode are short. circuited together. and brought out to respective single contact pins 2, 2, as is the case with the commercial watt fluorescent lamps In addition, there is provided in the- 3 known as 96-T-12. These lamps require approximately 565 volts between their electrodes for starting, and during normal operation may draw 425 milliamperes with a voltage drop of approximately 190 volts between the electrodes.

The lamps DI and DZ'are started and operated by means of an auto-transformer 3 comprising a primary winding P, a secondary winding S, and an auxiliary winding A. The primary winding P is adapted to be energized at terminals 4, 5 from a source of alternating current supply, which may for example be the usual 118 volt 60 cycle lighting circuit.

The main operating circuit for lamps DI and D2 comprises primary winding P, secondary winding S, a ballasting capacitor CI, and the lamps DI and D2 all connected in series. The secondary winding S has a high leakage reactance, which characteristic may be achieved by the use of the usual magnetic shunt in the core structure as indicated diagrammatically at 6. The primary and secondary windings are connected in aiding voltage relationship, as indicated by the arrows e and 65, and the sum of their open circuit voltages generated between terminal 4 and junction point I may be slightly in excess of the voltage required to start a single one of the lamps, for instance 580 volts. It will be understood that the voltage required to start a single one of the lamps is more than suificient for the operation and regulation of the two lamps in series after the discharges have been initiated. Due to the presence of capacitor CI, the lamps draw leading current from the operating circuit. However, by reason of the additional lag- I ging current drawn by the primary winding for magnetizing the core structure, the transformer as a whole draws substantially unity power factor current from the lighting circuit at terminals 4, 5.

The low current capacity auxiliary winding A is connected between terminal 4 of primary winding P and a junction point 8, which point is connected through a coupling capacitor C2 with the junction point 9 between lamps DI and D2.

The auxiliary winding may be either tightly or loosely coupled to the primary winding: if it is tightly coupled, capacitor C2 may be of lower voltage rating but must have a slightly higher capacitanc value than need be the case if the auxiliary winding is loosely coupled. In this particular example of the invention, the auxiliary winding is loosely coupled, the magnetic shunt being indicated diagrammatically at I I]. The auxiliary winding is connected in aiding voltage relationship with the primary and the secondary within the starting loop for lamp DI, as indicated by the arrow es. The starting loop comprises all three windings in series and is completed through capacitor CI, lamp DI, and capacitor C2. By reason of the presence of the two capacitors CI and C2, and especially by reason of capacitor 02 which is of small value and has a high reactance, the starting loop draws leading current to start lamp DI. A small value is purposely chosen for capacitor C2, since it need pass only the current necessary to initiate the formation of hot spots on the electrodes I ,I' of lamp DI. For commercial fluorescent lamps provided with filamentary activated electrodes, a minimum current of 100 milliamperes is generally regarded as satisfactory for initiating hot spots on the electrodes.

In operation, assuming that the normal supply voltage is applied to the input terminals 4, 5

of primary winding P, th sum of the primary and secondary open circuit voltages 6p and e.- is not, of itself, sufficient to cause the striking of an are within the two lamps in series. However, the voltage 6a developed in the auxiliary winding, when added to the primar and secondary voltages, results in a voltage which is more than suincient to strike an are within lamp DI. The open circuit voltage across lamp DI is represented by the broken line Vm in the vector diagram of Fig. 1b.

Hot spots are formed practically instantaneously on the electrodes of lamp DI, so that the voltage drop across it decreases nearly to its normal operating value, as indicated by vector Vm in Fig. 10. By reason of the inclusion of capacitor C2 in the starting loop including the three windings in series, the current flowing at this time is substantially of leading power factor, as indicated by the vector I. As is well known, the circulation of a leading current through a high leakage reactance winding produces a voltage drop which is in phase to add to the voltage induced in the winding by transformer action. Thus, after lamp D! had started but before lamp D2 has struck, the voltage between terminal points 4 and I is actually greater than the sum of the open circuit voltages of the primary and secondary windings. These conditions are indicated by the lengthening of the vectors es and es in Fig. 1c, and also by their slight retardation in phase occasioned by the fact that the current drawn by lamp Di leads the induced voltage by slightly less than a full The increase in the voltage vector Gs compensates to a certain extent for the voltage drop V01 across capacitor CI. Moreover the voltage drop across lamp DI, by reason of the fact that it is almost at right angles to the induced voltages e and es, causes at the worst but a very slight reduction and may even cause an increase in the voltage appearing between junction points 9 and i. This voltage, indicated by the dotted vector Vnz in Fig. 1c, is that which is effective in starting lamp D2. A5 a result, lamp D2 strikes and the discharge current increases to its normal value, generally in the neighborhood of 460 milliamperes for the commercial fluorescent lamps described. The conditions then are indicated by the vector diagram of Fig. 1d and the regulation of the discharge current is established by the excess in capacitive reactance of capacitor C I over the inductive leakag reactance of secondary winding S.

The successive operations which have been described, all take place within a very short interval of time amounting to a fraction of a second only. Thus, although the lamps start in sequence, the delay between them in starting is so brief that, to a casual observer, they appear to start simultaneously. The vector relations during normal operation of the lamps is indicated in Fig. 1d and it will be observed that the voltage produced by the auxiliary winding and indicated by vector a is largely cancelled by the voltage drop V62 across the high impedance of capacitor C2. Moreover these voltages are in such phase that they have but a very slight tendency to unbalance the currents circulating in the two lamps, in consequence of which the lamps light up with substantially equal brillance.

It will be observed that the inclusion of capacitor CI in the main operating circuit prevents any possibility of circulation of direct current through the primary and secondary windings. Thus even though one of the electrodes of either lamp D1 or D2 should become deactivated before. the other, so that the lamp in question might tend; to operate as a current rectifier, such an eventuality could only result in charging capacitor Cl, and the flow of direct current could not continue. Likewise, the inclusion or capacitor C2 in the ng loop ncluding the auxiliary winding, prevents of direct current in that winding. For iistanc-e, should one of the electrodes of lamp D2 become deactivated before the other, the most adverse result would be to char e up capacitor C2 and the iiow of direct current in the path cornprising winding A, capacitor C2, and lamp D2 could not continue. Accordingly, winding A need b designed to have a current carrying capacity merely suhioient to initiate the formation of hot spots on the electrodes of lamp DI. This is a distinct advantage over present sequence-start circuits in which provision must be made for the ice, but, by a rearrangement of parts, reconnecting the primary winding of the tansiormer from the supply lines whenever one of the lamps is removed from its socket or lamp-holder. This feature is generally referred to as a pri iary disconnect, and it is required by regula ing authorities to eliminate shock hazard for the resent type of circuit in view of the high voltages encountered.

Referring to 2a, transformer corresponds in general to transformer t of Fig. l and comprises primary winding P, loosely coupled secondary winding 3, and low current capacity auxiliary winding A. The auxiliary winding is tightly coupled to the primary in this example of the invention. The operating circuit for the two lamps comprises the secondary winding S between junction points l2 l3, balls-sting capacitor Cl, and lamps Di and D2 connected in series. The starting loop for lamp Di, beginning at junction poi t i t, includes primary winding P; auxiliary win ing A, coupling capacitor C2, secondary winding S and ballasting capacitor Cl. The windings are all connected in aiding voltage relationship, as may be seen by observing the direction oi" the voltage arrows 8p, es and s around the circuit.

The primary winding i adapted to be energized from the usual lighting circuit at terminals and Id. In order to disconnect the primary winding from the line whenever either lamp is removed from its socket, terminal Hi is connected to a contact ll, which in cooperation with a second contact it constitutes a short-circuiting connector for contact pin 2' of lamp Di. Corresponding contacts is and 2: form a short-circuiting connector for contact pin 2 of lamp D2. Contact iii of lamp Di is directly connected to contact 2! of lamp D2, and contact 28 oflamp D2 i connected to the primary winding P at junction point It will be understood that the contacts l'a', l8 and 2t, 2! have been diagrammaticaly represented and that their physical construction may correspond to either thesingle pin or the double pin short-circuiting'lampholders or la. This circuit follows the same more, a connection exists from the common junction point it of the lamps to terminal 23 of the primary winding. nected in additive polarity so that their respective voltages 65, and ea add up to produce a resultant voltage across lamp D! sufficient to start it. This voltage is indicated by the broken line vector V191 in Fig. 227.

After lamp D! has started, the secondary voltage 65, the voltage drop across capacitor C2 indi cated by V02 and the voltage drop across lamp DI- indicated by Vm, produce a resultant voltageindicated by Voz in Fig. 20, which starts lamp D2; It will be understood that the leading phase condition of the current vector 1, is caused, as in the circuit of Fig. 1, by the high reactance of the coupling capacitor C2. The operatin condition after the second lamp has started is shown by the vector-diagram of Fig. 2d, and it is similar to that of the circuit of Fig. la with the difference that the operating current for the two lamps does not circulate through the primary winding.

It will be observed that the circuit connections of Fig. 2a allow for disconnecting the primary of the transformer whenever either lamp is removed from its socket. Moreover the circuit connections permit the utilization of the primary voltage to aid the auxiliary windin voltage in starting the first lamp. Thus the voltage rating of the auxiliary winding may be reduced in proportion to the additional voltage injected into the starting loop by the primary winding and some economy in copper may thereby be achieved.

An example of specific apparatus embodying our invention and constructed described above in connection with Fig. 2c, successfully operated a pair of Watt 96-T-l2 fluorescent lamps requiring approximately 555 volts to start. The primary winding I? operated on a supply voltage of 118 volts at 60 cycles, the secondary winding S had an open circuit voltage of 589 volts, and the auxiliary winding A had an open circuit volt age of 340 volts. Capacitors Cl and C2 had ratings of 1.7 and 0.3 microiarads respectively. The

circuit started the lamps reliably even with the line voltage reduced to volts. At the rated line voltage of 118 volts, the voltage drop and current for lamp Di were 204 volts and 405 milliamperes respectively, and for lamp 2, 208 volts and 462 milliamperes respectively. Lamp Di consumed 76.5 watts, and lamp D2155 watts. any (lif ference in brilliance between the two lamps was practically unnoticeable to the eye.

Another embodiment of niy'invention is illustrated in 3a. The circuit is basically similar to that of Fig. l, and, by a rearrangement of parts, permits disconnecting the primary winding from the line whenever one of the lamps i removed from its socket. comprises primary winding P, a high reactance secondary winding S and an auxiliary winding A which is tightly coupled to the primary; The operating circuit for the two lamps comprises If either lamp is removed from its All three windings are con-- The transformer 25.

7 secondary winding S, lamp Di, primary Winding P, lamp D2 and ballasting capacitor CI. The primary winding is adapted to be energized from the usual lighting circuit at terminals 26 and 27, the former being connected to junction 28 of the primary winding through short circuiting connector 29 for contact pin 2 of lamp D2, and the latter being connected to terminal 39 through short circuiting connector 3| for contact pin 2 of lamp DI. Thus, if either lamp is removed from its connectors or lampholders, the primary circuit is opened and the shock hazard is eliminated. It will be appreciated that the main operating circuit comprises essentally the same ele ments as in the circuit of Fig. 1, but that the sequence has been varied by interchanging the positions of lamp DI and secondary winding S in order to achieve the desired disconnect feature.

The starting loop for lamp DI comprises all three windings connected in series and in aiding voltage relationship, and includes coupling capacitor C2. The starting loop may be traced, starting with electrode i of lamp Di, through secondary winding S, ballasting capacitor Cl, coupling capacitor C2, auxiliary winding A, primary winding 1?, and thence to electrode l of the same lamp.

The vector relations for the initial starting condition of the circuit are shown in Fig. 3b. The open circuit voltages of all three windings add up to produce a resultant VDl which starts lamp Dl without difficulty. After the first lamp has started, the vector relationships are as illustrated in Fig. 3c wherein the voltages es and 6p, together with the voltage drops Vm across lamp DI and VCl across capacitor Cl, produce the resultant V132 which starts lamp D2. The vector relationships after both lamps have started and normal operation has been achieved are illustrated in Fig. 3d.

While certain specific embodiments have been shown and described, it will of course be understood that various modiiications may be made without departing irom our invention. The appended claims are intended to cover any such modification coming within the true spirit and scope of the invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. Apparatus for starting and operating a pair of gaseous discharge devices from an alternating voltage source, comprising a transformer structure having a primary winding, a high leakage reactance secondary winding, and an auxiliary winding of low current capacity, connections for energizing said winding from said source, a ballasting capacitor, a leading current operating circuit comprising at least said secondary winding and said ballasting capacitor and connections for including both said devices in series, a second capacitor, and a leading current starting loop comprising connections for including one only of said devices, both said capacitors, and all of said windings in series, all of said windings being connected in aiding voltage relationship within said loop.

2. Apparatus for starting and operating a pair of gaseous discharge devices from an alternating voltage source, comprising a transformer structure having a primary winding, a high leakage reactance secondary winding, and an auxiliary winding of low current capacity, connections for energizing said primary winding from said source, a ballasting capacitor, a leading current operating circuit comprising said primary, and secondary windings, said ballasting capacitor and connections for including both said devices in series, said primary and secondary windings being connected in aiding voltage relationship, a second capacitor, and a leading current starting p comprising connections for including one only of said devices, both said capacitors, and all of said windings in series, said auxiliary winding being connected in aiding voltage relationship to the other windings within said loop.

3. Apparatus for starting and operating a pair of gaseous discharge devices from an alternating voltage source, comprising a transformer structure having a primary winding, a high leakage reactance secondary winding, and an auxiliary winding of low current capacity, connections for energizing said primary winding from said source, a ballasting capacitor, a leading current operating circuit comprising said secondary winding, said ballasting capacitor and connections for including both said devices in series, a second capacitor, and a leading current starting loop comprising connections for including one only of said devices, both said capacitors, and all of said windings in series, said primary and auxiliary windings being connected in aiding voltage relationship to said secondary winding within said loop.

4. Apparatus for starting and operating a pair of gaseous discharge devices from an alternating voltage source, comprising a transformer structure having a primary winding, a high leakage reactance secondary winding and an auxiliary winding of low current capacity, connections for energizing said primary winding from said source including in series a pair of short-circuiting connectors for contacting one side of each device at a common junction point, a leading current operating circuit comprising in series said secondary winding, a ballasting capacitor and connectors for contacting the other side oi each device, and a leading current starting 100p comprising said primary and auxiliary windings and a coupling capacitor connected in series between one side of one device at said common point and completed through said secondary winding and said ballasting capacitor to the other side of said one device, all three windings being connected in aiding voltage relationship within said loop.

5. Apparatus for starting and operating a pair of gaseous discharge devices from an alternating voltage source comprising a transformer structure having a primary winding, a high leakage reactance secondary winding and an auxiliary winding of low current capacity, connections for energizing said primary winding from said source including in series a pair of short circuiting connectors for contacting one side of each device, a leading current operating circuit comprising in series said primary winding, one device, said. secondary winding, a ballasting capacitor and the other device, and a leading current starting loop comprising said auxiliary winding and a coupling capacitor connected in series with said primary and secondary windings and said ballasting capacitor across said one device, all three windings being connected in aiding voltage relationship within said loop.

6. In combination, a pair of gaseous discharge devices, a transformer structure having aprimary Winding, a high leakage reactance secondary winding and an auxiliary winding of low current capacity, connections for energizing said primary winding from said source, a leading current operating circuit comprising at least said secondary winding, a ballasting capacitor, and said devices connected in series, and a leading current starting loop comprising one only of said devices, said ballasting capacitor, a coupling capacitor, and all of said windings in series and connected in aiding voltage relationship within said loop.

7. In combination, a pair of gaseous discharge devices, a transformer structure having a primary winding, a high leakage reactance secondary winding, and an auxiliary winding of low current capacity, connections for energizing said primary winding from an alternating voltage source, a leading current operating circuit comprising said primary and secondary windings, a ballasting capacitor, and both said devices connected in series, said primary and secondary windings being connected in aiding voltage relationship, and a leading current starting loop comprising one only of said devices, said ballasting capacitor, a coupling capacitor, and all of said windings connected in series, said auxiliary winding being connected in aiding voltage relationship to the other windings within said loop.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,950,396 Boucher Mar. 13, 1934 2,025,471 Osborne Dec. 24, 1935 2,295,757 Russel Sept. 15, 1942 2,298,935 Freeman Oct. 13, 1942 2,427,225 Mueller Sept. 9, 1947 2,436,400 Nathanson Feb. 24, 1948 2,509,188 Feinberg May 23, 1950 2,552,111 Peterson May 8, 1951 2,558,293 Feinberg June 26, 1951

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