An Uncoupled Search Coil for IPMSM Rotor Position Detection in Low-Speed Range

When the position sensor or the sensorless method fails, the search coil (SC) is often used as a backup option to provide a backup rotor position for the interior permanent magnet synchronous motor (IPMSM). Aiming at the problem that the conventional SC cannot detect the position of the backup rotor in the low-speed region of IPMSM, a design method of uncoupled SC (USC) is proposed in this article. The coupling relationship between the main winding and the SC is eliminated, and the rotor position is detected only by the inductance change of the USC itself. By actively injecting ultrahigh-frequency (UHF) sinusoidal voltage signal into the USC, the voltage feedback signal of USC itself is obtained, and the backup rotor position detection of IPMSM in the low-speed region is realized. The correctness of the theoretical analysis and the feasibility of the proposed method are verified by the experimental results.