Effect of open stator slots on the performance of an interior permanent magnet automotive alternator

This work describes a study of the effect of using open stator slots in an interior permanent magnet automotive alternator to increase its effective air gap and thus reduce its iron losses under field-weakening conditions. Analytical, finite-element and experimental results are compared for the back-electromotive waveforms, inductance saturation/torque curves, iron loss and field-weakening performance characteristics for the alternator with both semi-closed and with open slots. It is shown for the highly saturated machine considered, that using open stator slots can reduce the field-weakening iron loss without significantly affecting the machine performance.