Neutral Point Voltage Model of Stator Windings of Permanent Magnet Synchronous Motors with Magnetic Asymmetry

A mathematical model is described for predicting fluctuation in the neutral point voltage from stator windings to drive a permanent magnet synchronous motor (PMSM) in the zero speed-region. The model is derived under the assumption of small motor current and low motor rotation speed. It can be presumed from the model that the fluctuation represents the self-inductance DC, self-inductance AC, mutual inductance DC and mutual inductance AC components and the power supply voltage. It can also be presumed that the neutral point voltage offset for each voltage pulse pattern is generated from the magnetic asymmetry of the PMSM. This model will make it possible to design a PMSM with high sensitivity suitable for sensorless drives.