Patent ID: 7816801

Claim:
An over speed control circuit for a wind turbine generator system having a generator for generating an output voltage as a function of the speed of the generator, said generator having at least one pair of output terminals, a brake relay coupled across said output terminals and a brake relay control circuit for causing said brake relay to lockout for a predetermined time period any time the output voltage of said generator exceeds a first threshold and short out said generator output terminals until said predetermined time period has elapsed, the over speed control circuit comprising: a sensor for sensing the generator output voltage at the output terminals of said generator; a switch coupled across the output terminals of said generator which closes in response to a control signal; and a control circuit, responsive to said sensor, for generating a control signal to close said switch when said generator output voltage is greater than a second threshold and generating a control signal to open said switch when said generator output voltage drops below said second threshold defining a pulse width modulated (PWM) control signal, said second threshold being less than said first threshold.