Position Sensorless Estimation for Surface Permanent Magnet Synchronous Motor Using Eddy Current at Low-speed

This paper proposes a new method for rotor position sensorless estimation of surface permanent magnet synchronous motor (SPMSM), wherein the sensorless position control is very difficult when the motor is at a standstill and in low-speed regions as the motor has no magnetic saliency. In this method, conductive non-magnetic materials are pasted on the rotor. When a high-frequency voltage is applied, eddy current flows in these materials, and the inductance slightly changes depending on the rotor position. The position estimation of $0\sim 360^{\circ}$ at the electrical angle necessary for sinusoidal vector control commutation is realized using these inductance changes. Experiments show that the position estimation error is less than 50°, even though the rotor velocity is 10 rad/s.