Low speed position sensorless method for permanent magnet synchronous motors with closed-slot stator structure

A block commutation based position sensorless method for low speed regions has some advantages [6]-[11]. This method introduces "Induced Voltage caused by Magnetic Saturation (IVMS)". The IVMS based method can be applied to most permanent magnet synchronous motors (PMSM) with or without a saliency rotor structure. However, some motors that have a closed-slot stator structure cannot easily be driven by using this method, because of the complicated characteristics of the magnetic circuit. The detected IVMS is significantly affected by these characteristics. A new technique for closed-slot stator structure motors is proposed in this paper. A high frequency voltage injection is introduced in order to keep the magnetic saturation characteristics constant. The principle for it and our experimental results are also presented.