Uncontrolled generation in interior permanent-magnet Machines

The movement toward 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 permanent-magnet (IPM) machine operating in uncontrolled generation (UCG). This paper investigates the modeling and performance of IPM machines in UCG. The concept of the voltage-current locus is introduced to explain the presence of hysteresis in the machine stator current and this effect is experimentally demonstrated. The effect of nonidealities such as magnetic saturation and stator resistance are also examined, to achieve a more accurate steady-state and dynamic modeling of the machine behavior. The predictions of these models are tested against experimental results.