Abstract: In a control system for a step motor having a rotor and stator, small velocity coils are placed in the stator in quadrature to the main power phase windings. The velocity coils provide velocity feedback signals which are summed with current command signals to gradually damp the step motor. The damped step motor is effective in minimizing its rotor from oscillating about a desired stopping point.

Abstract: In a base drive circuit for a high power transistor, an external signal is applied to the circuit by an optical coupler. In response to the external signal, the circuit provides a positive current to the high power transistor in order turn it on. The positive constant current is characterized by an initial spike that prevents any localized hot spots from developing in the high power transistor and thereafter the positive current becomes constant. The circuit also provides a constant negative current when the external signal is removed, thereby quickly turning off the high power transistor. The optical coupler and a time delay device provide the circuit with high noise immunity.

Abstract: In a system having a plurality of electric motors which are rated at different voltages, a voltage control circuit enables the electric motors to be connected to a common power supply. The voltage control circuit determines a first voltage appearing between the positive bus of the power supply and the motor and a second voltage appearing between the negative bus and the motor. One voltage is inverted and then summed with the non-inverted voltage to provide an average voltage. The average voltage is compared to a reference voltage and when the average voltage exceeds the reference voltage, a limit signal is generated. The limit signal is used to prevent higher voltages from being applied across the motor.