Westinghouse Electric Corporation

Electric Power Research Institute Incorporated

Frank J Prines

Thomas C Matty

James H Franz, Jr

Ray S Kemerer

Martin I Norman

A current source gate drive circuit for simultaneous firing of a set of series or parallel thyristors is described. The circuit includes two current loops, each of which serves as a current transformer primary. Electrically insulating tubes enclose the current loops. Current transformer cores, around which are wound a certain number of secondary turns, surround the current loops, thus magnetically coupling the primary current of the current transformer to the secondary turns. Thyristor gate driver circuits are electrically coupled to the current transformer cores. Each of the thyristor gate driver circuits receives and rectifies ac current signals from the current loops and forms a current pulse train firing signal. Each thyristor gate driver circuit has a corresponding thyristor that is fired by the current pulse train firing signal. The thyristors operate at a high voltage, but are electrically isolated from the current loops by the insulating tubes. A current pulse shaping circuit is connected to the current loops and uses dual resonant LC circuits to generate ac current signals. The current pulse shaping circuit operates in a low voltage region and is electrically isolated from the high voltage region by the insulating tubes. The current pulse shaping circuit is activated by an edge-triggered signal. To prevent misfiring of the thyristors, thyristor firing command logic is used to generate a level-trigger signal. Level-triggered logic is responsive to the level-trigger signal, but not noise or transients, and produces a pulse train enable signal that allows the thyristors to be fired.

Current source gate drive circuit for simultaneous firing of thyristors

A direct current motor power controlling chopper apparatus is disclosed which determines the operational speed of one or more traction motors propelling a passenger vehicle along a track. The speed of the motor is established by changing the ON and OFF conduction ratio or duty cycle relationship of a thyristor switch device to determine the field current and the armature voltage of that motor. The present apparatus can provide a greater controlled range of motor speeds including a lower minimum OFF operation and a full ON capacity. In addition, the present apparatus provides greater reliability due to less thermal stress on the thyristor switch devices and fewer circuit elements required to provide an improved motor current control operation.

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Murrysville, PA, United States of America

Frank J Prines