Uncontrolled generation in interior permanent magnet machines

The movement towards higher power automotive electrical systems has spurred research into low-cost alternators capable of operating over a wide constant power speed range. A promising candidate for this application is a specially designed interior PM machine operating in uncontrolled generation. This paper investigates the modelling and performance of interior PM machines in uncontrolled generation. The hysteresis effect in the machine stator current is experimentally demonstrated and the concept of the voltage-current locus is introduced to explain this. The effect of non-idealities such as magnetic saturation and stator resistance are also examined, to achieve a more accurate steady-state and dynamic modelling of the machine behaviour. The predictions of these models are tested against experimental results.