Position Sensorless Estimation for Surface Permanent Magnet Synchronous Motor Using Eddy Current

The rotor position sensorless control of Surface Permanent Magnet Synchronous Motor (SPMSM) at a standstill and in the low-speed region is challenging because the motor has no magnetic saliency. Thus, the paper presents the development of a new rotor position-sensorless estimation method for SPMSM.In the proposed method, thin conductive non-magnetic materials are placed on the rotor surface. When the high-frequency voltage is applied, the eddy current flows through the materials, and the inductance is slightly changed depending on the rotor position. The position estimation from 0 to 360 angles (electrical degrees) where the field-oriented control (FOC) is required for SPMSM is realized using this inductance changes. The experiments show that the initial rotor position estimation error is less than 20 degrees ; thus, the proposed method is very useful.