US2358810A - Apparatus for starting and controlling discharge devices - Google Patents

Description

P 1944- w. J. KARASH 2,358,810

APPARATUS FOR STARTING AND CONTROLLING DISCHARGE DEVICES Filed April 21, 1942 Inventor": Walter J. Karash 8 His Attorn gq.

Patented Sept. 26, 1944 APPARATUS FOR STARTING AND CONTROL- LING DISCHARGE DEVICES Walter J. Karash, Annapolis, Md.. assignor to General Electric Company, a corporation of New York Application April 21, 1942, Serial No. 439,820

9 Claims. (01. 315-188) My invention relates to apparatus for starting and controlling electric discharge devices such as discharge lamps of the fluorescent type which are now coming into common use. It relates par ticularly to apparatus for starting a plurality of similar electric discharge devices connected to be operated in series from a source of current supply. As at present constructed a lamp of that type comprises a long transparent tubular envelope containing mercury vapor at a low pressure and having its side walls coated with a suitable phosphor which under the influence of an electric discharge through the mercury vapor produces fluorescence. The lamp electrodes which are mounted in the ends of the envelope are filamentary in form and are coated with a suitable electron emissive material. Such a lamp requires for its starting the a pplication of a voltage or electric impulse considerably higher than the voltage necessary to keep the lamp in operation after it has been started. A preheating of the electrodes of such lamps as they have been constructed heretofore has been essential in order to avoid excessive damage to the electrodes by the starting voltage and the attendant blackening of the lamp walls in the vicinity of the electrodes by the material knocked ofi them. By reason of recent developments made in such lamps particularly in the construction of their electrodes prior heating of the electrodes is not as essential to the prevention of injury to the lamp as heretofore; Because of the desire to avoid the time delay occasioned by electrode preheating, notwithstanding the fact that lamps as heretofore constructed were known to be seriously injured by being continually started without electrode preheating, apparatus has been used which would produce a voltage peak or impulse sufficiently high to make the lamp break down immediately upon its application thereto.

It is an object of my invention to provide improved apparatus for starting a plurality of similar electric discharge devices connected to be operated in series from a source of current supply whose voltage not only is less than the sum of the starting voltages of the devices but is less than the starting voltages of the individual devices.

My invention will be better understood from the following description taken in connectionwith the accompanying drawing and its scope will be pointed out in the appended claims.

Referring to the drawing, Figs. 1 to inclusive are circuit diagrams illustrating various embodiments of my invention.

In Fig. 1 two long tubular similar discharge devices which, for example, may be 40 watt fluorescent lamps are shown diagrammatically at I and 2 each provided with filamentary electrodes 3 5 ;which may or may not be short-circuited as shown by the drawing. The lamps I and 2 when started without any preheating of their electrodes may each require from 400 to 450 volts to start depending upon various conditions such as the geometry of the envelope and the temperature of the ambient. The envelopes of the lamps contain mercury vapor at low pressure and the side walls thereof have a phosphor thereon which when excited by a discharge through the mercury vapor produces fluorescence. The two lamps are connected to be operated in series from the secondary of the auto-transformer 5, the voltage of which secondary may, for example, be 360 volts, and the connection includes the ballast reactor 6 whose reactance may be 560 ohms. The transformer has its primary connected through the control switch 8 with the source 9 of alternating current supply which, for example, may be a 115 volt, cycle lighting circuit.

Inasmuch as the combined starting voltage of the two lamps in series is considerably higher than the secondary voltage of the transformer 5 it will be seen that the lamps when connected in series with the transformer, as shown, will not start without aid of other apparatus but after having been started they will continue to operate in series. Moreover, the voltage of the transformer is less than the starting voltage of either lamp. To effect the starting of the lamps, I have provided the circuit l2 shunting the lamp 2 and comprising the capacitor l3 and the winding 14 whose reactive impedances may be 5300 and 2860 ohms, respectively. The net reactance of the shunt circuit therefore is capacitive and the net reactive voltage of that circuit is opposite in character to the reactive voltage of the ballast 6. The winding I4 is the secondary winding of the transformer I5 whose primary winding I6 is loosely coupled with the winding I4 and may, for example, have a 1:1 turn ratio therewith. The primary Winding I6 is shown connected across the primary of the auto transformer 5,

hence is connected, through the switch 8 with the source of current supply 9. The winding l6 may, however, be connected across the secondary of the transformer 5 or across any desired portion thereof. By reason of the shunt circuit l2 substantially the full voltage of the transformer 5 to which is added the voltage of the secondary H of the transformer I5 is applied to the lamp I and that combined voltage, which may be approximately 4'75 volts, is sufficient to cause a discharge to start therein. After that lamp has started the current taken by it flows through the mediately starts and the current taken thereby traverses the ballast reactor I5 and the shunt circuit comprising the capacitor I3 and the winding I4. The resulting voltage then applied to the lamp 2 by the shunt circuit causes that lamp also to start. After it has started it provides a relatively low impedance path in shunt with the circuit I2. The two lamps I and 2 thereafter continue to operate connected in series across the secondary of the transformer 5 and since the ballast 6 is inductive the lamp current will be lagging. If it is desired that the energy taken from the source 9 shall be at approximately unity power factor one may connect a suitable capacitor represented at 4 across the secondary of the transformer.

In Fig. 2 the lamps I and 2, the transformer 5, and the transformer I5 are similar to the abovedescribed corresponding parts of Fig. 1. However, in this case the lamps operate with a leading current. The lamp ballast in Fig. 2 comprises the reactor I1 and the capacitor I8, the reactive impedances of which may for example be 630 and 1330 ohms respectively, and since the impedance of the capacitor is greater than that of the reactor the lamp circuit is capacitive. To effect the starting of the lamps I have provided the circuit I2 which shunts the lamp 2 and which comprises the reactor I9 and the secondary winding I4 of the transformer I5. This transformer unlike the transformer I5 of Fig. 1 has its primary and secondary windings closely coupled. The combined reactive impedances of the reactor I9 and the winding I4 may, for example, be 3000 ohms. The reactance of the shunt circuit in this case therefore is inductive and the reactive voltage of that circuit is opposite in character to the net reactive voltage of the reactor I1 and the capacitor I8 which comprise the ballast. The lamps I and 2 are started in a manner similar to that described above in connection with Fig. 1, lamp I first being started by reason of the combined voltage of the transformers 5 and I5 applied across it and after it has started, the lamp 2 being started by reason of the voltage of the shunt circuit I2 being applied to it. The two lamps I and 2 thereafter continue to operate connected in series across the secondary of the transformer 5 and since the ballast is capacitive the lamp current will be leading. If, in this form of my invention,, it is desired that the energy taken from source 9 shall be at approximately unity power factor one may connect a suitable reactor, as illustrated at 20, across the primary of the transformer 5 or, if preferred, he may con struct the core of the transformer with an air gap therein thereby to increase the exciting current of the transformer.

In hat form of my invention illustrated by Fig. 3 the transformers 5 and I5 or I5 of the forms illustrated by Figs. 1 and 2 are combined in the single transformer 22 having two secondary parts one shown at 23, above the-tap 24 and one shown at 25 below the tap 24. That part 23 of the transformer by which voltage, for example 360 volts, is applied to the two lamps in series corresponds to and is connected with the source of supply in a manner similar to that of the transformer 5 in Fig. l. The additional voltage which in the case of Fi 1 was obtained from the secondary winding I4 is in the case of Fig. 3 obtained from the secondary part 25, the voltage of which may, for example, be 240 volts. The circuit which shunts the lamp 2 in this case includes the capacitor 26, the reactor 21 and the secondary part 25, the reactances of which capacitor and reactor may,.; for example, be 5300 and 2400 ohms respectively. Inasmuch as the lamps in that form of my invention illustrated by Fig. 3 start in a manner similargtothat described above in connection with Fig. 1, it is thought to be unnecessary to include a description of how they start.

In that form of my invention as shown by Fig. 4 a single transformer is employed as in Fig. 3 but the transformer has a special form. It comprises the core 29 having the primary winding 30 which connects through the switch 8 with the source 9 and the secondary winding 3| provided with the tap 32 which divides tl.e winding into the two secondary parts 33 and 34. The core of the transformer has the magnetic shunt 35 and that leg thereof carrying the secondary winding 3I has the bridge gap 36 therein. The voltage which is applied to the two lamps in series is the voltage of the secondary part 33, which may be 240 volts, plus the voltage of the source 9 which if volts will be approximately 355 volts which is insufficient to start the lamps in series or to start either lamp alone. The lamp I connects across the source of supply 9 through the entire secondary winging 3|, the voltage of which may 475, and the reactor 31 and the ballast capacitor 38. By reason of these connections the lamp I may have applied to it approximately 590 volts and hence will be started.

After the lamp I starts the part 34 of the secondary 3| and the reactor 31 forms a shunt circuit about the lamp 2, and the reactive voltage of this shunt circuit being inductive is opposite to the reactive voltage of the ballast capacitor 38. The combined voltage due to the inductive reactance of this shunt circuit together with the voltage induced in the part 34 is sufficient to cause the lamp 2 to start. After the two lamps have been thus started they operate in series wih a -leading current.

That form of my invention illustrated by Fig. 5 employs the transformer 22' which is similar in construction and in the manner in which it is connected with the source to the transformer 22 in Fig. 3. The circuit includes two pairs of series connected lamps I, 2 and I, 2 which are supplied by the same transformer 22', the circuits of the two pairs of lamps being in effect a combination of the circuits shown in Figs. 2 and 3, the one circuit, namely that of the lamps I and 2, having a leading current and the other circuit, namely that of lamps I and 2 having a lagging current. Ballast for the leading circuit comprises the reactor I1 and the capacitor I8 which members may be similar to the members having the same numbers in Fig. 2 and ballast for the lagging circuit comprises the reactor 6 which may be similar to the member having the same number in Fig. 3. The circuit shunting the lamp 2 includes the reactor I 9 and the secondary part 25 which may be similar respectively to the reactor l9 and the winding I4 in Fig. 2 and the circuit shunting the lamp 2' includes the capacitor 26, the reactor 21 and the secondary part 25 which members may be similar to the members having the same numbers in Fig. 3. Inasmuch as the circuits shown in Fig. function in substantially the same manner to start the lamps, as has already been described in connectionwith Figs. 2 and 3, it is thought to be unnecsssary to again describe the operation of these circuits In any of the above described forms of my invention if it is desired that the currents taken by the two lamps be more nearly equal during their operation and also if greater stability of the lamps be desired one may build into the reactor.

or other winding included in the circuit shunting the lamp 2 or both lamps 2 and 2 in the case of the form shown in Fig. 5 somewhat more resistance than would otherwise be employed or, if preferred, he may insert a separate small resistor in that circuit.

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

1. In combination, a plurality of electric discharge devices, means having reactive impedance for connecting said devices to be operated in series from a source of alternating current whose voltage is less than the sum of the starting voltages of said devices, and a reactive circuit connected across one of said devices, the reactive voltage of said circuit being opposite in character to the reactive voltage of said impedance, and means in said circuit arranged to be energized from said source for increasing the voltage across said circuit to cause another of said devices to start.

2. In combination, a plurality of electric discharge devices, means having reactive impedance for connecting said devices to be operated in series from a source of alternating current whose voltage is less than the sum of the starting voltages of said devices, and a reactive circuit connected across one of said devices, the reactive voltage of said circuit being opposite in character to the reactive voltage of said impedance, said circuit including a winding, and means arranged to be energized from said source for inducing a voltage in said winding to increase the voltage applied by'said source to another of said devices.

3. In combination, a plurality of electric discharge devices, a step-up transformer, means having reactive impedance connecting said devices to be operated in series and energized from the secondary of said transformer, the voltage of which secondary is less than the sum of the starting voltages of said devices, a second transformer, and a reactive circuit including the secondary of said second transformer connected across one of said devicw, the reactive voltage of said circuit being opposite in character to that of said impedance.

4. In combination, a plurality of electric discharge devices, a step-up transformer the primary of which is adapted to be connected with a source of alternating current supply, reactive means whose net reactance is capacitive connecting said devices to be operated in series from the secondary of said transformer, a separate transformer having its primary and secondary windings closely coupled with each other and its primary connected with the primary of said stepup transformer, and an inductive reactive circuit including the secondary of said separate transformer connected across one of said devices.

5. In combination, a plurality of electric discharge devices, a step-up transformer, means having reactive impedance connecting said devices to be operated in series and energized from the secondary of said transformer the voltage of which secondary is less than the sum of the starting voltages of said devices, said transformer having an additional secondary, and a reactive circuit including said additional secondary connected across one of said devices, the reactive voltage of said circuit being opposite in character to that of said impedance.

6. In combination, a plurality of electric discharge devices, a step-up transformer having a plurality of secondary parts, inductive reactive means connecting said devices in series across one of said secondary parts, the voltage of said one part being less than the sum of the starting voltages of said devices, and a capacitive reactive circuit including another of said secondary parts connected across one of said devices.

7. In combination, a plurality of electric discharge devices, a step-up transformer having a plurality of secondary parts, capacitive reactive means connecting said devices in series across one of said secondary parts, the voltage of said one part being less than the sum of the starting voltages of said devices, and an inductive reactive circuit including another of said secondary parts connected across one of said devices.

8. In combination, a plurality of similar electric discharge devices, means having reactive impedance for connecting said devices to be operated in series from a source of alternating current whose voltage is less than the starting voltage of each of said devices, and a circuit connected across one of said devices including means for increasing the voltage applied by said source to another of said devices to cause it to start and including reactive means, the reactive voltage of which is opposite in character to that of said first mentioned means, for causing said one device subsequently to start.

9. In combination, a plurality of similar electric discharge devices, means having reactive impedance for connecting said devices to be operated in series from a source of alternating current whose voltage is less than the starting voltage of each of said devices, and a circuit connected across one of said devices including other reactive means together with means arranged to be energized from said source for raising the voltage applied to the other of said devices from said source, to cause it to start, the reactive voltone device is caused to start.

WALTER J.

Images