Rotor Position Detection Method for Permanent Magnet Synchronous Motors Based on Search Coil Mutual Inductance

This paper addresses the problem of traditional search coils being unable to detect the rotor position of permanent magnet synchronous motors (PMSMs) in low-speed regions. A rotor position detection method based on the mutual inductance effect of search coils is proposed. By designing the structure of the search coils, the mutual inductance effect of the armature winding on the search coils and the influence of the coil's back electromotive force on rotor position detection is eliminated. An ultrahigh-frequency sinusoidal voltage signal with a frequency of 100 kHz is injected into the search coils. The rotor position is calculated by extracting the effective value of the mutual inductance voltage, achieving rotor position detection across the full speed range of the motor. An experimental prototype containing search coils was fabricated, and the experimental results verified the correctness of the theoretical analysis and the effectiveness of the proposed method.