A Modified Method for Initial Rotor Position Detection of Brushless DC Motor Based on Voltage Vector Injection

In order to realize the rapid detection of initial rotor position of permanent magnet brushless DC motor (BLDCM) and reduce the application cost, an improved method of initial position of the motor rotor detection is proposed by combining the salient polarity and magnetic saturation of the motor itself. By successively injecting three voltage vectors into the motor winding and collecting the DC side current $i_{\text{dc}}$ at the specified time, the terminal voltage comparison circuit is also designed to compare the magnitude relationship between the inactive phase terminal voltage of c or b and $U_{\text{dc}}/2$ under the action of effective vector, which can quickly and accurately judge that the motor rotor position is actually in a 30 degree sector. The feasibility and correctness of the proposed method are verified by the experiments.