A Back-EMF Based Sensorless Speed Control of Four Switch BLDC Motor Drive

The objective of this work is to create an economical drive system for a BLDC motor with lesser number of switches. In this paper, a new technique is introduced to control the speed of a Four switch Brushless DC (FSBLDC) Motor drive, by sensing the back-emf developed across the stator windings. Conventionally, the speed can be monitored by using speed encoders and are very expensive, also create noises while placing on the motor shaft. So a sensorless speed detection algorithm is developed by sensing the back-emf and the speed is calculated. Here the switching losses of the machine are abated by exciting the motor with a Four Switch Inverter with lesser number of switches. The system simulation and its results are included in this paper.