US2182633A - Ignitron starter circuits - Google Patents

Description

. Dec. 5, 1939. KLEMPERER 2,182,633

IGNITRON STARTER CIRCUITS Filed Jan. 13,-1938 2 Sheets-Sheet l INVENTOR Hans Mempgre:

WITNESSES:

y/ w x TM ATTORN EY Dec. 5, 1939. H. KLEMPERER 2,182,633

mm'raon STARTER cmcurws Filed Jan. 1:5, 1938 2 Sheets-Sheet 2 time WITNESSES: I FP/zgya-A INVENTOR 0%. 6M I Hans ff/gmperen ATTORNEY Patented Dec. 5, 1939 UNITED STA IGNITRON STARTER CIRCUITS Pennsylvania Application January 13, 1938, Serial No. 184,833

2 Claims.

My invention relates to vapor-electric converters and it has particular relation to an excitation system for such converters.

In the operation of make-alive type converters,

'5 considerable difiiculties arise in keeping ionization low especially at the beginning of each reverse half cycle of alternating current. As a result of the presence of quantities of ionized vapor, backfire becomes frequent. According to the teachings of prior art, suitable electric valves, preferably ofv the grid-controlled hot-cathode type, are utilized to supply the make-alive current to the make-alive electrode of such converters. High average starting ciu'rents were 1 required. to excite the starter of the main tube. Moreover, the moment of starting was somewhat uncertain due to the nature of the front of the starting current. Uncertainty in starting results in self-starting and the restriking of delayed main arcs and fluctuations in the over voltage.

In the construction according to my invention, the above-mentioned difliculties are eliminated. The exciting circuit comprises a charging circuit and a discharging circuit. The charging circuit consists of a condenser, reactor and a unidirectional conductor in series with the make-alive electrode. During the inverse half cycle of the anode voltage, the condenser is charged to a voltage which is modified by the changing magnetic field of the reactor. The charging current can be kept low by extending the charging time over the full half cycle.

The discharging circuit consists of an electric valve such as a grid-controlled valve, a resistor for controlling the time constant of the discharge and the aforesaid condenser. determined moment during the forward half cycle, the condenser discharges across the starting electrode and the resistor. It will be preferred to discharge the condenser in a relatively short period of time, thereby obtaining a high peak current.

It is, therefore, an object of my invention to provide a starting circuit requiring a relatively low charging current during the inverse half cycle of the alternating current and a relatively high exciting current during the forward half cycle.

It is another object of my invention to provide an excitation system which makes the momentof starting very accurate.

Another object of my invention is to provide for a control system adapted to make the discharging circuit obstructive while the charging circuit is conductive.

Still further, it is an object of my invention At a pre- Other objects and advantages of my invention will be apparent from the detailed description,

when taken in conjunction with the accompanying drawings, in which Figure 1 is a schematic illustration embodying the excitation system according to my invention;

Fig; 2 is a graphical illustration showing the relationship between charging current, discharge current and condenser voltage with respect to time;

Fig. 3 is a view similar to Fig. 1 showing a modified means for controlling the time of discharge;

Fig. 4 is a graphical illustration showing the relationship between charging current, discharge current and condenser voltage with respect to time according to the modification of my invention; and

Fig. 5 shows another modification of a starting circuit according to my invention.

Apparatus according to Figure let my inven tion comprises a suitable evacuated envelope 3 containing a mercury pool forming the cathode 5, having dipping into it a small rod of resistant material forming the make-alive electrode 1. Opposite to the cathode 5 and in close proximity with it is the other mainelectrode or the anode 9. I

Alternating current is supplied from a suitable source, such as a transformer H, the direct current consuming device l3 being located between the transformer II and one of the main electrodes 5. The make-alive electrode I is in serted in the rectifying chamber 3 and is in permanent contact with the vaporizable cathode 5. In series with the make-alive electrode 1 is a suitable condenser l5, a reactor IT and a unidirectional conductor l9, such as an arc-discharge tube, or a copper oxide rectifier.

The discharge circuit 2! comprises a suitable grid-controlled discharge device 23 in series with a suitable resistor 25. The condenser l5 forms part of the discharge circuit 2| during alternate half waves of the alternating current. A suitable phase shifting device 2'! may be connected to the grid-controlled discharge device 23 for varying the timing of the impulse relative to the anode voltage.

In the operation of my converter 29, alternating current is applied to the main electrode 5 and 9 of the converter and when the potential applied to the anode 9 is negative, the potential will flow through the uni-directional conductor I9 charging the condenser i5 up to the supply voltage. The alternating current in passing through the reactor ll induces a voltage due to the changing magnetic field and the condenser I5 may be further charged to a potential considerably above the supply potential. The charging time and the voltage of the condenser I5 may be adjusted by varying the amount of inductance in the reactor I! and a resistor l8 may be used to further modify the charging time within fairly wide limits by changing or cancelling the additional resistor. By providing a gridcontrol for the rectifier IS, a still further modification of charging time may be obtained. I prefer to keep the charging current low by extending it over the full half cycle, making where L is the inductance of the coil IT, C is the capacitance of condenser l5 and w is 2 "Ir f, f denoting the frequency of the supply voltage. At the termination of the inverse half cycle, the uni-directional conductor i9 blocks further passage of the charging current. During positive half cycle, the grid-controlled discharge device 23 is positive with respect to the cathode 5 so that the charged condenser 15 discharges through the starting electrode 1 and a suitable resistor 25, which I provide, thereby starting the arc to the main anode 9. The point on the cycle at which the breakdown occurs can be selected by aphase shift control 2'! (Figure 3) of the gridcontrolled discharge tube 23. A resistor 25 is inserted in the discharging circuit 2| to control the duration of the discharge current.

Fig. 3 of my invention illustrates one modification of a starting circuit. In this modification, the starting electrode 1 does not come in contact with the cathode 5. An auxiliary source of supply potential, which is in. phase with the anode potential, is applied to the converter 29. It is believed that separate excitation has an advantage over the load current ignition, for the operation 'of the converter 29 is then independent of load conditions. A suitable phase shifter 28 is connected between the alternating-current supply 4 and the rectifier I9 whereby the phase of the supply voltage maybe effectively changed. Likewise, a suitable phase-shifter 2'! is connected between the alternating current supply 4 and the grid-39 of the grid-controlled discharge tube 23 to change the phase relation of the grid voltage of tube 23 relative to the anode voltage.

A suitable transformer 33 having a high ratio of transformation is connected between the dischargingcircuit 2| and the starting electrode I so that with a relatively small voltage impressed produce a spark between the starting electrode 1 and the cathode 5 and consequently start the main anode current in that valve.

It is apparent from inspection of Figs. 2 and 4 that the exciting current is maintained low during the entire inverse half cycle. One may select, at random, any point on the forward half cycle to start the discharge. It is also apparent that a starting current of steep-wave front may be obtained at a predetermined moment, which makes starting accurate and also prevents restriking of improperly started main arcs.

It is to be understood that direct current may be used, utilizing this same circuit in case the converter 29 runs as an inverter. The rectifier l9 must be provided with a grid to block the supply current While the condenser 15 is being discharged.

While, for purposes of illustration, I have described certain specific embodiments of my invention, it will be apparent that many changes and modifications can be made without departing from the true spirit of my invention and the scope of the appended claims.

I claim as my invention:

1. An arc discharge device comprising a main valve having a plurality of main electrodes, a starting electrode in permanent contact with one of said main electrodes for initiating a cathode spot therein, a capacitor, a reactor and a uni-directional conductor in series relation with said starting electrode, a source of alternating current for energizing said capacitor through said unidirectional conductor said unidirectional conductor permitting current to flow to said capacitor during the inverse half cycle of alternating potential, and a discharging circuit including a valve for blocking the flow of current while said capacitor is being charged.

2. An arc discharge device comprising a main valve having a plurality of main electrodes, a starting electrode in permanent contact with one of said main electrodes for initiating a cathode spot therein, a capacitor, a reactor and a uni-directional conductor in series relation with said starting electrode, a supply of alternating current for energizing said capacitor through said unidirectional conductor said uni-directional conductor blocking the current flow to said capacitor during, the positive half cycle, and a discharging circuit including a valve for permitting said capacitor to discharge through said starting electrode while said unidirectional con ductor is non-conducting.

HANS KLEMPERER.

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