Analysis on iron loss of switched reluctance motor under PWM mode

This paper aims to establish a modified variable coefficient calculation model to analyse the control parameter effect on the iron loss of switched reluctance motor under pulse width modulation (PWM) mode.

The finite element model is solved to get the flux density by python language. Due to non-sinusoidal flux density feature and the effect of PWM excitation, the Fourier transform is applied in consideration of harmonic components. To improve the accuracy of iron loss computation, the effect of minor loops is considered by using the rain-flow counting method.

When the speed fluctuates around the set speed and the fluctuations are relatively small, it is useful to reduce the iron loss with smaller duty ratio and turn-on angle or greater duty ratio and smaller turn-off angle. The iron loss is less affected by chopping frequency, while the iron loss increases obviously with higher conduction angles. The iron loss under non-energy-returnable-voltage-chop mode is greater than energy-returnable-voltage-chop mode.

The modified variable coefficient MIEM5 iron loss model is proposed to improve the accuracy of iron loss calculation. Then the control parameters such as duty ratio, chopping frequency, turn on angle and turn off angle are analysed under PWM mode.