SPEED CONTROL METHODS OF BLDC MOTOR DRIVES

Abstract

The Permanent Magnet Brushless Direct Current Motor (BLDC) uses a simple structure with high efficiency, high reliability, and maintenance-free, a solid competitor for the induction motor (IMs), conventional DC Motor, and PMSM. The PM Synchronous Motor (PMSM) has a sinusoidal back emf and requires sinusoidal currents to produce constant torque. In contrast, the PMBLDC has a trapezoidal back emf and requires square/rectangular currents to produce constant torque. A complex electronic switch circuitry is required for commutation, which requires a gating signal as an appropriate timing pulse for proper utilization of the interaction of stator and rotor magnetic field to generate the torque. There are plenty of methods available for speed control, direct, indirect, and modern complex methods. The application of any method depends upon the type of requirement, with every method having its own merits and demerits. A rare-earth magnet effectively reduced the size and weight. Sensorless speed control further reduced the volume and maintenance due to poor performance of position sensor subjected to abnormal atmospheric conditions (High Temp, Humidity, altitude, etc.) and poor workmanship.