US2535698A - Electric valve excitation circuit - Google Patents

Description

Dec. 26, 1950 A. SCHMIDT, JR 2,535,698

ELECTRIC VALVE EXCITATION CIRCUIT Filed Dec. 28, 1949 inventor": August Schmidt, Jr?

His At torn ey Patented Dec. 26. 1950 ELECTRIC VALVE EXCITAT ION CIRCUIT August Schmidt, Jr., Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application December 28, 1949, Serial No. 135,352

1 Claim.

This invention relates to electric valve excitation circuits and more particularly to an excitation circuit for continuously exciting electronic devices utilizing an ionizable medium.

For certain purposes, it is desirable to excite continuously the ionizable medium used in electronic devices such as ignitron tubes. In order to maintain the cathode spot, it has been necessary to supply a relatively large current to the holding anode element such as is utilized in devices of the mercury pool cathode type. Ordinarily this large current would be larger than would be necessary under normal conditions to maintain the cathode spot in order that the spot would be maintained during abnormal conditions. Such large currents either require an excitation circuit made up of relatively large component parts or are characterized by high energy losses in the circuit.

An object of this invention is to provide static means for controlling in a precise fashion the excitation of a continuously energized electronic device having an enclosing envelope containing an ionizable medium.

Another object of the invention is to provide automatically operable means for limiting the energy required to maintain continuously the cathode spot in an electronic device of the type which utilizes an ionizable medium such as mercury.

Still another object of the invention is the provision of an arrangement for automatically reestablishing the excitation of an electronic device of the continuously excited ionizable medium type should the device momentarily become deenergized.

In accordance with my invention, the flow of current from the holding anode of the cathode spot is utilized to control a variable impedance connected in series with the ignitor element and the components are arranged so that the impedance in series with the ignitor is promptly de creased by a substantial amount should current cease to flow from the holding anode to the cathode. In this way, the ignitor is promptly reenergized and the cathode spot reestablished.

While I have shown my invention as applied to an electronic device of the well known ignitron type, it will be understood that it is not limited thereto and that the invention can be used in conjunction with any electronic device having an enclosing envelope with an ionizable medium and a holding anode disposed therein.

My invention will best be understood by reference to the accompanying drawing in which the numeral I represents the enclosing envelope of an electron device of the ignitron type. A metallic closure 2 is joined to the envelope I] through insulating ring 3. Closure 2 forms a part of the cathode. Also disposed within the envelope are a main anode 4, a control grid 5, a holding anode 6 and an ignitor 'I.

As is well known, flow of current through the ignitor circuit vaporizes the mercury pool contained in metallic closure 2 and the spot so established on the mercury pool is maintained by the holding anode 5 which is of such a potential with respect to the cathode that a flow of electrons is maintained from the cathode to the anode 8.

For energizing ignitor 'I, a transformer 8 energized from a source of alternating current potential 9 is used. The secondary winding of transformer 8 is arranged in series with the ignitor I, and a unidirectional conducting device ID prevents the flow of current from ignitor I to transformer 8 through device Ill. Also included in the excitation circuit for ignitor I is a winding II forming a part of a variable reactor I2 having a magnetizing winding l3 and a control winding I4. Direct current potential for the holding anode 6 is supplied by rectifier I5 and transformer I6 from the alternating current supply 9. A suitable current limiting resistor I1 is connected in series with the holding anode 6.

The magnetizing winding I3 and the holding winding I4 are oppositely wound and are constructed of a proper number of turns so that the magnetomotive force produced by winding I3 is partially or completely ofiset by the magnetomotive force of winding I4 if holding anole 6 and its associated circuit is conducting a current, i. e. when a cathode spot is being maintained on the surface of the mercury pool. Magnetizing winding I3 is constructed so that the reactor I2 will become saturated should a current cease to flow in winding I4. In this way, the reactance of winding II is substantially reduced upon failure of current to flow from holding anode 6 to the mercury pool. This substantial reduction in the overall impedance of winding I I results in a relatively large current through ignitor I and its associated circuit from the secondary oi transformer 8. This large current is of sufficient magnitude to reestablish the cathode spot should the holding anode fail momentarily to maintain this spot.

Since the arrangement shown in the drawing and described thus far is capable of automatically reestablishing the cathode spot, it is not necessary to supply a large current through the holding anode 6 and its associated circuit. Thus a minimum of current is required through this circuit and the component parts thereof can be of a relatively small size without incurring substantial energy losses in the holding anode circuit.

While I have shown and described a particular embodiment of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from my invention in its broader aspects, and I, therefore, intend in the appended claim 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:

In combination, an electric discharge device of the type employing an enclosing envelope and comprising therein an ionizable medium, a cathode, an ignitor, and a holding anode, an energizing circuit connected to said ignitor for causing the emission of electrons by said cathode, saturable impedance means connected in said circuit, means including a source of direct current for energizing said holding anode, a magnetizing Winding energized with direct current and effective to saturate said impedance means, and a control winding the energization of which is dependent upon the flow of current from said holding anode to said cathode for opposing the magnetizing efifect of said magnetizing Winding.

AUGUST SCHMIDT, J R.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 20 2,426,046 *Pakala Aug. 19, 1947 2,441,987 Boyer et a1 May 25, 1948

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