Abstract: A prime mover which is equipped with an electric speed governor may produce adequate electrical power output through a shaft driven permanent magnet alternator to run the electric speed governor. However, initially an auxiliary power source must be connected to the electric governor until the permanent magnet alternator becomes self-sustaining. The present invention is an electrical circuit which will automatically provide start-up power from an auxiliary source and then switch to the permanent magnet alternator. Certain safety interlocks are provided in case of speed pick-up failure.