Analysis of Freewheeling on the Starting Method Based on Inductance Variation for Brushless DC Motor Drives

Abstract

In recently years, the starting becomes the bottleneck problem of development for brushless DC motors without position sensors. One method, ‘Initial Rotor Position Estimation’, based on inductance variation can be used to start the motor with position feedback, but the performance is affected by the process of freewheeling. Therefore, this paper studies on the two freewheeling modes, which are the freewheeling mode through power and the mode not through power, in the universal three-phase bridge in the system of brushless DC motors. Besides, the paper analyzes the influence caused by different freewheeling modes. The analysis results show that the freewheeling mode through power is more suitable for the starting technique than the other one. On the basis above, the simulation carried out in MATLAB/Simulink verifies the validity of the theoretical analysis.