(The) brushless DC motor driven by 12-step voltage source inverter

Abstract

The speed control of a brushless dc motor driven by a new 12-step VSI(Voltage Source Inverter) is presented in this paper. The circuitry of the static converter consists of a line commutated controlled rectifier, a transistor inverter employing a new 150(deg) firing method and a regenerative inverter to return the residual airgap energy to the three phase power source. A three phase wound rotor induction motor, where the rotor is energized by a dc source, is employed so that it can be considered as a cylindrical synchronous motor. The firing moment and sequences of the VSI switching devices are controlled by the absolute rotor position sensor only. The motor can be self-started and a transistor inverter eliminates any commutation difficulty at low speed. The motor speed is controlled by PI controller implemented by Z-80 microprocessor.