a motor control circuit for submersible pumps has features to prevent restarting while the electric motor is backspinning . the circuit includes a sensor for sensing the voltage produced by the residual magnetism in the rotor of the motor while it backspins . the voltage sensed is amplified , then rectified and compared with a reference voltage that is preset . the reference voltage corresponds to a voltage produced during backspinning at a selected maximum amount tolerable when restarting . the dc pulses are filtered to provide a corresponding voltage , then compared to the reference voltage . the control circuit is disabled from allowing a restart , either manual or automatic , when the corresponding voltage is greater than the reference voltage .