Position Sensorless Estimation for Surface Permanent Magnet Synchronous Motors Using Eddy Currents with Loads at a Low speed

Position sensorless control of surface permanent magnet synchronous motors (SPMSMs) in low-speed regions is challenging because the motor has no magnetic saliency. Several methods using the block commutation drive technique to overcome this problem have been proposed; however, the rotor position is estimated only every 60° owing to the features of the block commutation drive method. Therefore, in this study, we proposed a novel sensorless rotor position estimation method by pasting the conductive nonmagnetic materials on the rotor. When high-frequency voltage is applied, eddy currents flow through the materials and the inductance slightly changes depending on the rotor position. In this study, estimating the continual rotor position from 0° to 360°, in which the sinusoidal vector control commutation is necessary rather than the block commutation drive method, was realized using these inductance changes. Based on the experimental results, we found that the rotor position could be continually estimated from 0 to 360°, which is necessary for sinusoidal vector commutation for an SPMSM with a position estimation error of approximately 6°, although the rotor velocity was low at 1.59 % of the rated velocity and 12 % of the rated load was applied.