Trapezoidal Speed Control of BLDC Motor

In the past few years, the brushed direct current motors are being replaced by brushless direct current (BLDC) motors. This is mainly because BLDC motors have higher efficiency, speed and torque. In order to drive a BLDC motor a control circuit is required. Frequently used control circuit is an inverter. There are two types of speed control techniques using control circuit for BLDC motor namely 120° square-wave commutation and 180° sinusoidal commutation. The 120° square-wave commutation also known as trapezoidal commutation, is easy to implement and has less cost as compared to 180° sinusoidal commutation. In trapezoidal commutation, the current is controlled through two terminals of the motor and the third terminal is disconnected from the power source. This paper presents the 120° square-wave commutation for speed control of BLDC motor using SEMIKRON inverter, TI's Launchpad F28069M and Altair embed (VisSim) software. The results of the speed control are evaluated and verified using experimental results. Simplicity and low-cost operation are the advantages of this control strategy.