Power contactor and control circuit

Power application control circuitry for an electric load comprising

• power relay means including contacts connected between a source of electrical current and the load for controlling the application of power to said load,
• arc suppression means associated with said contacts of said power relay means including
• auxiliary contacts on said power relay means,
• semiconductor means having power conducting terminals connected across said contactor and a gate terminal connected through said auxiliary contacts to a gate energizing signal, and
• actuator means for closing said auxiliary contacts just prior to either the closing or opening of said contactor and for opening said auxiliary contact just after either the closing or opening of said contactor, whereby the potential across said contactor is momentarily reduced to prevent arcing during opening or closing thereof and whereby said gate energizing signal is not maintained when said contactor is closed thereby protecting said semiconductor means against overload in the event said contactor should develop an appreciable contact resistance or fail to close,
• steering relay means including contacts connected between the source of power and the input terminals of the load for controlling the character of the current flow through said load for causing the current to said load to have a first characteristic when said steering relay means is deenergized and to have a second characteristic when said steering relay means is energized,
• control circuit means connected to said power relay means and said steering relay means for controlling the operation thereof, said control circuit means including a circuit interconnection through said steering relay means whereby when current of the second characteristic is desired, the contacts of said power relay means close only after said steering relay is energized, said control circuit means further including time delay means for delaying the deenergization of said steering relay means until after the contacts of said power relay have opened and current to the load is completely removed.

A circuit for applying power to a three phase electrical motor and for controlling the direction of rotation of the motor, comprising:

• first, second and third power relay contactor means connected between a source of electrical current and the motor,
• arc suppression means connected across each of said power relay contactor means,
• first, second and third motor power input terminals,
• means for connecting said first power relay contactor means to said first power input terminal,
• steering relay contactor means connecting said second and third power relay contactor means to said second and third power input terminals in a first combination, when not actuated, such that said motor will rotate in a forward direction, and for connecting said second and third power relay contactor means to said second and third power input terminals in a second combination, when actuated, such that said motor will rotate in a reverse direction,
• power relay actuator means for actuating said first, second, and third power relay contactor means such that power is applied to said first power input terminal and to said steering relay contactor means,
• steering relay actuator means for actuating said steering relay contactor means,
• means for energizing said power relay actuator means directly such that said first, second and third power relay contactor means are actuated for forward rotation of said motor, and
• means for energizing said steering relay actuator means and said power relay actuator means such that said first, second and third power relay contactor means are actuated after said steering relay contact means is actuated, and means for causing said steering relay contactor means to remain actuated until after deactuation of said first, second and third relay contactor means,
• whereby actuation and deactuation of said steering relay contactor means is not performed while power is applied thereto, thereby preventing arcing across said steering relay contactor means.

Power application control circuitry for an electronic load comprising

• power relay means including contacts connected between a source of electrical current and the load for controlling the application of power to said load,
• semiconductor means having power conducting terminals connected across the contacts of said power relay means, and a gate electrode,
• switching means for applying control current to said gate electrode,
• means for actuating said switching means for causing control current to be applied to said gate electrode just prior to either the opening or closing of the contacts of said power relay means and for thereafter removing said control current whereby the potential across said power relay contacts is momentarily reduced to prevent arcing during opening or closing thereof and whreby said control current is not maintained when said contacts are closed thereby protecting said semiconductor means against overload in the event the power relay contacts should develop an appreciable contact resistance or fail to close,
• steering relay means including contacts connected between the source of power and the input terminals of the load for controlling the character of the current flow through the load for causing the current to the load to have a first charactistic when said relay means is deenergized and to have a second characteristic when said relay means is energized,
• control circuit means connected to said power relay means and said steering relay means for controlling the operation thereof, said control circuit means including a circuit interconnection through said steering relay means whereby when current of the second characteristic is desired, the contacts of the power relay means close only after the steering relay means is energized, said control circuit further including time delay means for delaying the deenergization of the steering relay means until after the contacts of the power relay means have opened and current to the load is completely removed.