US1891114A - Electric translating circuit - Google Patents

Description

Dec. 13, 1932. A 1,891,114

ELECTRIC TRANSLATING CIRCUIT Filed March 30, 1951 In ventor':

Camil ASabbah,

His Attorney.

Patented Dec. 13, 1932 UNITED STATES PATENT OFFICE A GAME A. SAIBBAI-I, or scHENEc'rAnY, NEW YORK, ASSIGNOR To GENERAL ELECTRIC COMPANY, A oonroRArroN on NEW YORK ELECTRIC rnANsLATING oinourr Application filed March 30, 1931. Serial No. 526,336.

My invention relates to electric translating circuits and more particularly to such circuits utilizing electric valves of the mercury pool cathode type.

5 In many electric translating circuits, and more particularly in such circuits adapted to transmit energy from a direct current sup ply circuit to an alternating current load circuit the use of electric valves of the mercury pool cathode type has beenfoundparticular ly advantageous because of the relatively large amounts of power which may be handled at ordinary operating voltages. It is wellknown that the voltage required to 1 initiate an arc in such a valve is considerably higher than the normal voltage drop in the valve when conductive. It has become common practice to provide such valves with auxiliary keep-alive electrodes to maintain the cathode in an ionized condition in cases where the valve carries current intermittent ly. In certain cases it becomes necessary to provide means for initiating an arc in the electric valve, used in such a translating circuit, upon energization of the direct current circuit, the auxiliary keep-alive electrodes being energized thereafter from some portion of the translating circuit.

It is an object of my invention therefore to provide an improved electric translating circuit including an electric valve of the mercury pool cathode type in which means is provided for automatically initiating an arc in the valve upon energization of the direct current circuit.

It is a further object of my invention to provide an improved electric translating circuit energized from a direct current supply circuit and including an electric valve of the mercury pool cathode type provided with auxiliary are maintaining electrodes in which means is provided for impressing a high transient voltage upon the auxiliaryelectrodes, upon energization of the direct current circuit, for initiating an arc in the electric valve. p In accordance withone embodiment of my invention an electric translating circuit comprising anapparatus for transmitting energy i from a direct current supply circuit to an al l current load circuit, and including a pair of electric valves of the mercury pool cathode type is provided with means for initiating an arc in the valves upon energization of the direct current circuit. The electric valves are provided with auxiliary arc maintaining electrodes which are normally energized through a transformer from the alternating circuit of the apparatus to maintain the cathodes of the valves in an ionized state. A circuit including a reactance, such, for example, as an oscillating circuit, is connected across the direct currentcircuit of the apparatus and includes circuit interrupting means, which may be a contaotor operated by a solenoid, the coil of which comprises the reactance. The circuit including the auxiliary electrodes and the cathodes of the electric valves is connected in parallel with the reactance so that the discharge of the'reactance causes a transient voltage to be impressed upon the auxiliary electrodes. 7 I

For a betterunderstanding of my invention, together with other and further objects thereof, reference is had to the follow- 7 ing description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims. The single figure of the accompanying drawing illustrates my invention as applied to an 8 ternatir apparatus for transmitting energy from a direct current supply circuit to an alternating current load circuit. I

Referring now to the drawing, I have illustrated an arrangement for transmitting 8 energy from a direct current supply circuit 10 to an alternating current load circuit 11. This apparatus may be any of the several types well known in the art but I have illustrated by way of example, an apparatus of the type known in the art as a parallel inverter such as is disclosed and broadly claimed in United States Letters Patent No. 1,800,002, granted April 7, 1931, upon the application of E. F. V. Alexanderson. This apparatus comprises a transformer l2 havinga secondary winding, connected to the alternating current circuit 11 and a primary [winding provided with an electrical midpoint connected to the positive side of the direct current circuit and with two end terminals connected to the negative side of the direct current circuit through electric valves 13 and 14. Each of electric valves 13 and 14 is provided with an anode, a control grid, a mercury pool cathode, and auxiliary are maintaining electrodes 15, which may be of any of the several types well known in the art, although I have illustrated by way of example auxiliary mercury pools contained in side chambers of the envelopes of the electric valves. A commutat-ing capacitor 16 is connected between the anodes of electric valves 13 and 14. The auxiliary electrodes 15 of electric valves 13 and 14 are connected to their respective cathodes through opposite halves of the secondary windings of exciting transformers 17 and 18, respectively, and a reactance 19 which comprises the onerating coil of an electromagnetic switch 20. The switch 20 is preferably of a quick opening type and as illustrated may be of the mercury type. The control grids of electric valves 13 and 14 are connected to their common cathode circuit through opposite halves of the secondary winding of grid transformer 21 and a current limiting resistor 22. The primary windings of the transformers 17. 18 and 21 are energized from the alternating current circuit, the connections to the winding of the transformer 21 including a capaci tor 23 for determining the frequency of the alternating current delivered to the c rcuit 11 in case that circuit is not independently energized. In certain instances it may be desirable to connect a reactance 24 and a capacitor 25 in series with the reactance 19 and switch 20 in order to produce a transient with the desired characteristics to excite the auxiliary electrodes 15. A high resistance 26 is preferably connected across the capaci tor 25 to allow any residual charge to leak off. I have shown a conventional switch member 27 by means of which the direct current circuit of the apparatus may be energized.

The general principles of operation of the power converting apparatus described above will be well understood by those skilled in the art, or may be found explained in detail in the above mentioned Alexanderson patent. In brief, when one of the electric valves 13 or 14 is made conducting, for example, valve 13, current will flow through the left-hand portion of the primary winding of transformer 12 producing a potential in the primary winding connected in circuit 11 and in the right hand portion of the primary winding and charging the commutating capacitor 16 to substantially twice the direct current po tential of the direct current circuit. This induced potential impresses a transient upon the grid circuit comprising the primary winding of transformer 21 and capacitor 23 and, after a predetermined interval, the grid of the electric valve 14 is made conductive. Commutating capacitor 16 now discharges through the valves 13 and 14 instantly 1nterrupting the current in the valve 13. In this manner current is periodically transferred between the valves 13 and 14, producing and alternating current in the secondary winding of the transformer 12 connected to the load circuit 11. In many cases the potential of the direct current circuit will not be sufficient to initiate an are through the valves 13 and 14 unless their cathodes are ionized, and, since the alternating current circuit is not energized until after the valves become conductive, additional means must be provided for ionizing the cathodes of the valves 13 and 14. For example, assume that switch member 27 has just been closed. A transient of current will flow through the circuit including capacitor 25, reactor 24,

switch 20 and reactance 19. This transient current flowing through reactance 19, which comprises the operating coil of the electromagnetic switch 20, will operate the switch 20 to open its contacts at the same time interrupting the transient current. Because of the high reactance of the winding 19, any tendency to interrupt the current flowin therein suddenly will produce a high translent voltage. This voltage is impressed upon auxiliary electrodes 15 of the valves 13 and 14 through the secondary windings of exciting transformers 17 and 18 and initiates an arc from the auxiliary electrodes 15 to the main cathodes of the valves. This ionization of the cathodes of valves 13 and 14 enables the apparatus to function as described above. The alternating current supplied by the circuit 11 to the transformers 17 and 18 maintains the keep-alive are between the cathodes and the auxiliary electrodes 15 of the electric valves. It will be noted that this keepalive current flows through the reactance 19 and thus maintains the contacts of the switch member 20 open. Any residual charge which may have been upon the capacitor 25 at the interruption of the current transient in the oscillating circuit will slowly leak off through the resistor 26.

While I have illustrated and described what I at present consider the preferred embodiment of my invention, it will be obvious to those skilled in the art that various chan es and modifications may be made without eparting from my invention and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

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

1. In combination, a direct current supply circuit, a normally deenergized alternating current load circuit, means for transmitting energy therebetween including an electric valve of the mercury pool cathode type pro- Vided with auxiliary arc-maintaining electrodes, means for initiating operation of the apparatus upon energization of the direct current circuit comprising reactance means connected to be energized momentarily and simultaneously therewith and means for exciting the auxiliary electrodes with the discharge of said reactance, and means for normally exciting said auxiliary electrodes from said alternating current circuit.

2. In combination, a direct current supply.

circuit, a normally deenergized alternating current load circuit, means for transmitting energy therebetween including an electric valve of the mercury pool cathode type provided with auxiliary are maintaining electrodes, means for initiating operation of the apparatus upon energization of said direct current circuit comprising anoscillatory circuit connected across said direct current circuit and including an electromagnet and normally closed contacts operatedthereby, and a circuit including said auxiliary electrodes connected in parallel to said electromagnet, and means for normally exciting said auxiliary electrodes from the alternating current circuit of the apparatus.

In witness whereof, I have hereto set my hand.

CAMIL A. SABBAH.

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