DR-05: Study on the Reduction of Eddy Current Loss of Permanent Magnet Synchronous Motor considering PWM

Recently, permanent magnet synchronous motors to which PWM (Pulse Width Modulation) control is applied are mainly used. PWM control is a technique that can modulate not only the frequency of the output voltage but also the magnitude, and is a control method that generates pulses for turning on and off each phase switch. In addition, it is a technology that uses switching to control analog circuits with digital output, which is effective for motor control. In general, when designing a motor using FEM, a sinusoidal current waveform is used. When the motor is driven through PWM control, current contains harmonic components compared to sinusoidal current, and these harmonic components have a great influence on eddy current loss generated in permanent magnets. When designing a motor, it is possible to obtain more accurate analysis results by using a current waveform considering PWM control instead of using a conventional sinusoidal waveform. In this paper, the eddy current loss of the permanent magnet, which has a great effect on the performance of the motor, is compared using the division of the permanent magnet, and the eddy current loss of the permanent magnet is derived and compared using the sinusoidal current waveform and the current waveform considering PWM control. In a synchronous motor, since the rotating speed of the rotor and the speed of the stator rotating magnetic field are the same, eddy current loss for the fundamental wave does not occur. However, when harmonics exist, eddy current loss of permanent magnets occurs due to harmonics. Due to the harmonic components of the PWM current, the Total Harmonic Distortion(THD) of the line-to-line voltage under load increased by about 167% compared to the simulation result through the sinusoidal current waveform in comparison to the existing sinusoidal current waveform, and the torque ripple also increased by about 33%. When the magnet was not divided, the model using a sinusoidal current waveform measured 5.79W, and the model using a current waveform considering PWM measured 7.26W. When the magnet was divided, the model using a sinusoidal current waveform measured 0.416W and PWM The model using the considered current waveform measured 0.604W.