Protection of variable frequency power systems from excessive peak electrical potentials

Abstract

A method of protecting an electromechanical power transfer system from excessive peak electrical potentials, the power transfer system comprising a prime mover, a dynamoelectric machine coupled to the prime mover for generating multiphase alternating current (AC) power, and at least one multiphase AC electrical load coupled to the dynamoelectric machine by way of a multiphase AC power bus, the dynamoelectric machine having a control coil responsive to control current for varying power supplied to the electrical load, comprises the steps of: analysing electrical potentials on the power bus to generate analysed power bus characteristics; comparing the analysed power bus characteristics to predetermined power bus characteristics; simultaneously shunting power across the power bus and reducing control current to the control coil for the dynamoelectric machine when the analysed power bus characteristics approximate the predetermined power bus characteristics to reduce the measured electrical potentials; and simultaneously terminating the shunt of power across the power bus and restoring the level of control current to the control coil for the dynamoelectric machine after a selected delay period to automatically restore power to the electrical load.