Magnetising flux saturation in variable-speed inverter-fed induction motor drives

Saturation in induction machines is important in a number of applications and it has to be accounted for in the model of induction machines. The paper considers operation of saturated power converter-fed variable speed induction machines. It is shown that in simple drives, such as current-source inverter fed induction machines and resonant parallel inverter fed induction machines, it is sufficient to apply an appropriate saturated induction machine model in the simulation. In these cases, there is no need to analyse and understand the mechanism of saturation influence on the drive behaviour. However in vector controlled drives, where instantaneous flux value is controlled, it is important to realise how and when saturation will affect performance of the drive. Finally, due to very fast rate of change of saturation level in the machine, the only adequate method of saturation compensation seems to be application of an open-loop saturation adaptive rotor flux estimator