Abstract: A load dump circuit for a wye connected electric generating machine includes a silicon controlled rectifier connected between the common terminal of the wye and one of the output terminals of the machine. A Zener diode sensing circuit is connected to the common wye terminal and to the control terminal of the controlled rectifier for rendering the controlled rectifier conductive to shunt the output windings in the event of an excessive voltage being developed thereacross as a result of a rapid load reduction or similar condition. Means are also provided to terminate field excitation during the shunting condition.

Abstract: An over-voltage protection circuit for an electric generating machine having a controlled rectifier for shunting the output winding of the machine in the event of an over-voltage condition includes impedance means connected in series with the controlled rectifier and regulation circuitry responsive to current flowing through the impedance means for preventing the excitation of the field when the controlled rectifier is conductive. An improved triggering circuit including a Zener diode and a transistor switch is employed to assure proper triggering of the controlled rectifier.