Brushless DC motor has been widely used in industrial applications because of its low inertia, fast response, high power density, high reliability and maintenance free. It is usually supplied by a mechanical sensor on the rotor shaft to detect the position and speed. But it has drawbacks such as a) it increases the rotary inertia of the rotor shaft as well as dimension of the motor, b) it is easily affected by temperature, humidity and shape, c) it increases the cost of entire setup. This paper provides a review of the literature based sensorless operation of brushless dc motor. Methods explained are 1) using measured currents, voltages, fundamental machine equation and algebraic manipulations, 2) using observers, 3) using back-emf methods, 4) sensorless starting techniques and 5) with novel techniques.
Brushless DC Motor (BLDCM), Sensorless techniques, Trapezoidal back emf
