Analysis and Suppressing Speed Fluctuations in Brushless DC Motors

The fluctuations in both speed and torque magnitudes during operation are among the major disadvantages of brushless DC motors. These fluctuations occur due to both the commutation of the inverter switches and the phase winding inductances. This case can lead to major problems, especially in applications which are required constant speed and constant torque. In this work, it was aimed to reduce speed fluctuations that occur in brushless DC motors. Firstly, the simulation model was created by using the dynamic equations of the brushless DC motor. Secondly, a region selective circuit was designed for use in commutation regions. Finally, the commutation signals were generated from the magnitude of the torque produced by the motor. Consequently, the proposed technique was controlled under different speed conditions and was shown that the speed fluctuations can be reduced without the difficult calculations of the commutation time. According to the results obtained, it was observed that the speed fluctuations were significantly reduced.