Impact of Maximum Back-EMF Limits on the Performance Characteristics of Interior Permanent Magnet Synchronous Machines

Interior permanent magnet (IPM) synchronous machines are vulnerable to uncontrolled generator (UCG) faults at high speed that can damage the inverter. One approach to reducing this risk is to impose limits on the maximum machine back-EMF voltage at top speed. This paper presents the results of a comparative design study that clarifies the nature and extent of the penalties imposed on the IPM machine metrics and performance characteristics as a result of imposing progressively tighter values of back-EMF voltage limits. As an alternative to limiting back-EMF and penalizing machine designs, this paper also investigates the effectiveness of the system-side protection approach to the same UCG fault problem