Sine-wave drive for PM motor controlling phase difference between voltage and current by detecting inverter bus current

Permanent magnet synchronous motors (PMSMs) with sinusoidal waveform back electromotive force (EMF) are widely applied to home appliances to reduce acoustic noises and energy consumption. PMSMs are generally controlled with a sine waveform current, sine-wave drive for PM motor controlling the phase difference between the voltage and the current has been proposed to control PMSMs efficiently. That method detects the motor current, accurately calculates the phase difference between the motor voltage and the motor current, appropriately controls it to an optimum point [1]-[2]. This paper proposes a new method which doesn´t need to detect the motor current directly but estimates the phase difference between the voltage and the current by sampling the voltage of shunt register which is placed to detect an over current to inverter devices. We have achieved a lower cost and reliability for an inverter circuit of home appliances.