PM-assisted reluctance synchronous motor/generator (PM-RSM) for mild hybrid vehicles: electromagnetic design

This paper introduces the conceptual design and finite-element method analysis of a permanent-magnet-assisted reluctance synchronous motor/generator for mild hybrid vehicles where a large constant power speed range (6:1) is required and machine volume, converter peak kVA, and battery size are the main constraints. Careful flux-barrier and permanent-magnet sizing, high magnetic saturation, and current density are the main requirements for maximum torque production with constraint volume. A specific tangential force density of 4.33 N/cm² is obtained. Rated (continuous) power-battery limited is 2.5 kW at 42 V dc, from 1000 to 6000 r/min. The peak torque of 140 N·m is obtained at 202 A (rms/phase) and can be secured up to 500 r/min. Peak power is still 7.85 kW at 6000 r/min at 42 V dc with an efficiency of 90%. Preliminary results on a prototype are also available.