Variable-frequency electric drive with a function of compensation for induction motor asymmetry

Operation of a variable-frequency electric drive with damages in power electric circuit of the motor stator results in asymmetry of the motor phase current charge, increase of heating losses in certain phases, occurrence of variable components of electromagnetic torque and consumed power. Such operation modes significantly influence both motor operation and frequency converter operation, as long operation of a semiconductor energy converter under such conditions results in considerable overheat of certain switches, and later - in complete breakdown. The paper presents results of research of two devised vector-control systems with a function of compensation for motor broken windings influence on the characteristics of the variable-frequency electric drive. The first case deals with a possibility of compensation for electromagnetic torque variable component that causes additional vibrations of the motor. In the second case a possibility of compensation for consumed active power variable component is demonstrated; it results in reduction of heat overload of both separate phases of the motor and semiconductor switches of the frequency converter.