Advantages of Inset PM Machines for Zero-Speed Sensorless Position Detection

The aim of this paper is to analyze the behavior of a sensorless control system based on a high-frequency signal injection combined with an inset permanent-magnet (PM) motor. The rotor position of a synchronous PM motor with anisotropic rotor can be detected by the control system which superimposes a high-frequency signal to the fundamental stator voltage. The corresponding high-frequency current is modulated by the rotor anisotropy and used to determine the rotor position. These techniques are effective at zero and at low motor speed. Both saturation and cross-coupling have a heavy influence on the correct rotor position detection. In order to highlight the effectiveness of the sensorless technique, the tests are carried out at various operating conditions.