DC Reluctance Machine — A Doubly-Salient Reluctance Machine with Controlled Electrical and Mechanical Power Ripple

Abstract

Doubly-Salient Reluctance Machines (DSRMs) sidestep many of the issues with permanent magnet and induction machines and embody the lowest cost and simplest manufacturing of the motor technologies. Major drawbacks to RMs have been (1) the need for failure-prone electrolytic capacitors, (2) large torque ripple, and (3) acoustic noise. Conventionally, these drawbacks have been addressed independently either through (1) excitation control or (2) machine design, but not as a holistic system or solution. This disseratation presents a design for high-efficiency low-cost RM while producing smooth output torque and avoiding pulsating inverter input current and the associated electrolytic capacitor. We propose a method for shaping the machine reluctance profile to reduce machine torque ripple to a desired level (here, <5%) without compromising on machine efficiency or power density, a Shaped Reluctance Machine (ShRM). Furthermore, a comprehensive approach which combines both phase excitation control and machine design to cooperatively address the excursions of input and output powers from their average values which results in less than 5% ripple for both electrical and mechanical net power — essentially a DC Reluctance Machine (DCRM). Compared to conventional practice in DSRMs, electrical power ripple is reduced by 85 times and torque ripple is reduced by almost 20 times, while overall efficiency, torque density, and power density are maintained.