Iron Loss Measurement of Interior Permanent Magnet Synchronous Motor

The International Electrotechnical Commission (IEC) as well as the Japanese Industrial Standards (JIS) proposes standard methods for the measurement of soft magnetic material iron loss density. Under these measurements, the magnetic field applied to the material is strictly unidirectional and purely sinusoidal. However, in an electrical motor, the magnetic path is not straightforward, and the magnetic field can be largely rotating. Moreover, when the motor is driven by an inverter using power electronic devices switching at high frequency, the magnetic field can have large high order harmonic content thus harmonic distortion. Because of these effects, simply using the iron loss density data obtained by standard measurements, in order to predict the motor total iron losses, can be inaccurate. Accordingly, ways to measure and separate the effect of different parameters on the iron losses of an interior permanent magnet synchronous motor (IPMSM) are described in this chapter. In the following sections, experimental methodology and numerical calculation methods are first explained. Then, the effects of the inverter switching frequency, PWM modulation index, and dead-time, along with the effect of the motor load on the total iron losses, are investigated.