A Sensorless Commutation Strategy for a Brushless DC Motor Drive System Based on Detection of Back Electromagnetic Force

In this paper a sensorless commutation strategy for a brushless de motor without using any analog filters or integrators is proposed. This technique is based on the estimation of the hack-EMF of the non-conducting phase using the three terminal voltages of the machine with respect to the half of the DC voltage. A constant phase shift of 30 is achieved, independently front the operating point of the motor. The performance of the system using this strategy is assessed by simulation in MATLAB/SIMULINK software. Two operating scenarios are investigated at different rotor speeds in order to prove wide operation range of the proposed strategy.