Abstract: A method for providing a smooth transition to powered operation in a motor control system in which a variable voltage inverter regulates power to the motor on a volts per Hertz basis. The method is particularly applicable to systems for energizing and rapidly gaining control of a motor driving a load in which the motor armature is turning at the time that power is supplied from the variable voltage converter. The method is implemented by sweeping the frequency of the excitation applied to an alternating current motor while holding the magnitude of the excitation at a level sufficient to prevent over current excitation of the motor.

Abstract: A dynamic brake control system for an alternating current motor powered by a variable voltage, variable frequency inverter which regulates the speed of the motor. An AC to DC converter converts AC line power to DC power with the DC power being transferred to the inverter via a DC link. During electrical dynamic braking, the inverter functions to transfer power from the motor to the DC link. The torque available to the motor during braking is a function of the receptivity of the DC link. Link receptivity controlled by a resistance connected to the link in which the resistance is modulated at a frequency dependent upon the incoming AC line frequency at the converter. The modulation is binarily controlled so as to minimize ripple current on the DC link without the necessity of providing high frequency control of the modulating electronics.