All-speed-range drive for surface permanent magnet synchronous motors by combined use of two position sensorless methods

A new position sensorless method is proposed for surface permanent magnet synchronous motors in all speed regions. In this method, two sensorless methods are switched in accordance with the rotating speed. In low speed regions, an Induced Voltage caused by a Magnetic Saturation (IVMS) based method is used. This method is switched to a back EMF based sinusoidal current method at a medium or high speed. Some control blocks are commonly used for both methods. Therefore, the methods can be switched smoothly and rapidly. The basic idea and the experimental results are described.