Abstract-This paper describes a high-power brushless interior permanent-magnet (PM) automotive alternator which does not use an inverter. The "inverterless" alternator is designed with a high back electromotive force voltage and high reactance, and acts as a constant current source over much of its wide constant power operating speed range. In this configuration, a switched-mode rectifier can be used to regulate the dc output voltage and current, which avoids the complexity and high cost of an inverter. An analysis of the modeling and performance of interior PM machines in this inverterless topology is described. Experimental results showing an outstanding constant power speed range are presented for a 6-kW concept demonstrator machine tested using a three-phase resistive load to simulate inverterless operation.

Abstract-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.Index Terms-Interior permanent magnet (IPM), uncontrolled generation (UCG), voltage-current loci.