US2334568A - Apparatus for starting and controlling electrical discharge devices - Google Patents

Description

Nov. 16, 1943. Y H. w. LORD 2,334,568

APPARATUS FOR STARTING AND CONTROLLING ELECTRICAL DISCHARGE DEVICES Filed Jan. 22, 1942 Figl.

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Invent o1:

Haroki W. Lord,

Patented Nov. 16, 1943 APPARATUS FOR STARTING AND CONTROL- LING ELECTRICAL DISCHARGE DEVICES Harold W. Lord, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application January 22 1942, Serial No. 427,789

Claims. (01. 1'l6124) and having the inner surface of its side walls coated with a suitablephosphor 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 emitting material. Such a lamp requires for its starting the application of a voltage impulse considerably highenthan the voltage necessary to keep the lamp in operation after it has been started. Inasmuch as the voltage required to startsuch a lamp is materially less if the lamp electrodes are heated prior to the application 01 the starting voltage and since less injury is done to the lampif its electrodes are preheated it has become common practice to f heat the electrodes to the point of electron emission prior to the application of the starting voltage. A

To avoid the delay incident to the preheating of the electrodes instant starting of such lamps has been eifected by applying thereto a voltage sumcient to make them break down immediately even with cold electrodes. For that purpose use has been made 01' a high reactance step-up transformer designed to give the necessary high start-' ing voltage but such apparatus has had the ob-. -.iection of being electrically inemcient and of beheating. This apparatus, in part, functions as ballast impedance for the device.

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

Referring to the'drawing, Fig. 1 is a circuit diagram illustrating one embodimentof my invention; Fig. 2 is a diagram showing the volt-ampere characteristic of a special form of reactor which I employ; Fig. 3 is a diagram of the voltage wave or impulse which I obtain; and Fig. 4 is a circuit diagram showing a modification.

In Fig. l the electric disharge device i is represented as a fluorescent lamp which, for example, may be a 40 watt lamp having a length of 48 inches and a diameter of 1 V. inches such lamps being in common use at the present time. Ithas a tubular glass envelope containing mercury vapor at low pressure and a small quantity of neon or argon gas. The electrodes 2 are filamentary in form being wound in close coils and constructed of a refractory metal wire such as tungsten coated with a suitable electron emitting material such as barium'oxide or strontium oxide. Since the electrodes are not provided with means for raising their temperature to the point of electron emission prlor to the application of the starting voltage to the device as is commonly done, they are preferably constructed to have a very small mass whereby when a voltage impulse of sufficient intensity is applied to the deing cumbersome, since it has poor material utitially' preheated.

In accordance with my invention, briefly, I have provided apparatus which when connected between a discharge'device and a source of alternating current supply will produce. a voltage peak and will superpose it on the voltage wave supplied to the device, the maximum value of the voltage impulse thus produced being suflicient to cause the device to start without electrode previce to make, it break down without prior heating of the-electrodes, the electrodes or portions thereof at least have their temperatures raised so quickly that little loss of the electron emitting material and only a very slight blackening of the adjacent ends of the envelope may occur. The

two ends of each electrode are shown connected together in order that the operating current may be supplied to the electrode at both ends thereof. However, if desired the current may be supplied to the electrode from one end only.

The device which may have a voltage drop thereacros of volts when running is connected to be energized from the source of alternating current supply I which may be a 60 cycle, .230 volt lighting circuit through the connections 4 and l and controlled by the switch 0. Arranged in one of the connections, for example 4, is the non-linear reactor 1 shown as comprising the three-legged laminated core 8 on the middle leg of which is the winding 9. The core may be built up of E-shaped laminations and bar laminations,

adjacent E laminations being reversely arranged in order to break the joints with the bar laminations in the usual and well known manner. The middle leg of each E lamination has a narrow transverse rectangular opening I punched therein, the openings in the several laminations forming the stack being in alignment and constituting an air gap, while the neck II at each end of the opening saturates through the major part of each half cycle of the applied voltage. Such an air gap is commonly termed a "bridged gap. A reactor such as is shown in Fig. 1 and described above has a volt-ampere characteristic like that represented at I2 in Fig. 2, the bend l3 in the curve marking the point at which saturation occurs in the necks l I.

Connected in shunt with the device I is reactive means comprising the reactor H and the capacitor IS in series therewith. The reactance of the capacitor predominates; hence the net reactance of the reactive means is capacitive. The reactor I4 is shown as comprising a core having its middle leg provided with the air gap 16 and with the winding I'I thereon. The core may be built up of E-shapedlaminations l8 and T-shaped laminations l9, adjacent laminations being reversely arranged to break the joints therebetween in the usual manner and being stacked to cause the air gap faces of the laminations to aline with each other.

It is stated above that the net reactance of the reactor H and the capacitor I is capacitive. The amount of capacitance provided by the capacitor is such that the reactors I and I4 and the capacitor l5 form a resonant circuit during those parts of each cycle of the applied voltage when the necks II or the reactor 1 are desaturated. By the saturation of the necks, the circuit is detuned until desaturation again occurs later in the cycle. Thus, twice in each cycle at approximately those times of maximum applied voltage a condition of resonance exists. Ateach of those times, therefore, the voltage across the shunt circuit, which is that applied to the device I, is very materially increased and constitutes a peak. Actually the peaks occur slightly after the crest of the voltage wave of the source, the delay probably being due to the inductive effect of the reactor [4 and the iron losses therein.

In Fig. 3, I have shown at 22 the voltage wave of the source and at 23 the voltage waveapplied to the device having the peaks 24 whose maximum value is ample to cause the device to break down without any preheatin of its electrodes. The device having broken down continues to operate ballasted by the reactor 1 in the well known manner. The resonance condition no longer obtains and since the discharge in the device shunts the reactor 14 and the capacitor the ener y loss in those members is relatively small.

Instead of employing the reactor 1 of the construction shown and described, one may, if desired, obtain the same result by the use of two separate reactors as shown at 21 and 28 in the modification comprising Fig. 4. The former is a high reactance reactor whose core forms a closed magnetic circuit which is adapted to saturate. Its winding 29 is connected in series with the winding 30 on the'reactor 28 whose core has the air gap 3| therein. The core of the reactor 21 may be built of E-shaped laminations and bar lamination and the core of the reactor 28 may be built up of E-shaped laminations and T-shaped laminations. In this modification the reactor 21, since it saturates, functions like that part of the reactor I which includes the necks II; the reactor 28, since it has an air gap, functions like that part of the reactor 1 which includes the air gap Hi. In the circuit shunting the device I are the reactor I4 like the corresponding reactor of Fi l and the capacitor I5 also like the corresponding capacitor in that figure. The three reactors and the capacitor in thi modification function in cooperation to produce a voltage peak such as that and in the manner already described above.

Although the voltage peaks produced with my invention are sufilcient to make the device break down with cold electrodes one may, if desired, connect the shunt circuit to the device in such a manner that the current of that circuit passes through the electrodes thereby producing a certain amount of heating thereof. Such an arrangement is shown in the modification comprising Fig. 4 where the electrodes are included in series with the several reactors and the capacitor.

I have chosen the particular embodiments described above as illustrative of my invention and it will be apparent that various other modifications may be made without departing from the spirit and scope of my invention which modifications I aim to cover by the appended claims.

What I claim as new and desire to secure by Letters Patent 0f the United States is:

1. In combination, a source of alternating current supply, an electric discharge device, a first reactive means connected in series with said device across said source, and a second reactive means comprising an inductive and a capacitive member, the net reactance of which members is capacitive, connectedin shunt with said device, said first reactive means comprising a part constructed to saturate during parts of both half cycles of said current and said first and second reactive means being constructed to form together a circuit which resonates when said part is desaturated.

2. In combination, a source of alternating current supply, an electric discharge device, reactive means connected in series with said device across said source and reactive means connected in shunt with said device, said first mentioned reactive means having a core part constructed to saturate during parts of both half cycles of said current and a core part having an air gap, all of said reactive means together comprising a resonant circuit when said saturable core part is desaturated.

3. In combination, a source of alternating current supply, an electric discharge device, a reactor connected in series with said device across said source and reactive means connected in shunt with said device, said reactor having a core, one part of which is constructed to saturate and another part of which has an air gap therein, and said reactor and said reactive means comprising a resonant circuit when the first mentioned part is desaturated.-

4. In combination, a source of alternating current supply, an electric discharge devic a reactor connected in series with said device across said source and reactive means connected in shunt with said device, said reactor having a core including a part provided with a bridged gap at which saturation occurs and a winding on said part, the reactance of said reactive means being such that resonance occurs during those parts of the applied voltage wave at which said bridged gap is desaturated.

5. In combination, a source of alternating currestricted parts constructed all to saturateduring parts of each half cycle of said current, said first and second reactive means forming together a circuit which resonates when said parts are 5 desaturated.

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