Design and control of ultra-high speed switched reluctance machines over 1 million rpm

Abstract

The objective of this dissertation is to design, manufacture and control an ultra-high speed switched reluctance machine (UHSSRM) for applications requiring speeds of over 1 million rpm. First, a novel high-strength, high-power-density and high-efficiency rotor design for UHSSRM is proposed. The optimal length of the rotor stack is determined based on the cohesive zone model (CZM), using high-strength adhesives to increase the mechanical bonding and reliability between the rotor and the shaft. A rotor dynamics analysis of the proposed rotor structure is also conducted. Then, a detailed electromagnetic design of the whole 4/2 UHSSRM for applications over 1 million rpm is proposed, which includes pole pair number selection, air gap design, dimension calculation, material selection, winding selection and windage torque calculation. Next, a constant volts per hertz (V/f) control and an optical-based direct position control for UHSSRMs are proposed. The method optimizes the switching on and off angles to generate the maximum output torque, which is verified on a larger 4/2 SRM at 100,000 rpm. After that, a multi-physics acoustic analysis of UHSSRMs is proposed based on finite element analysis (FEA). The model is proven to be very accurate in predicting the noise level of UHSSRMs at 100,000 rpm by experiment. Finally, for the first time in the literature, the proposed design is integrated with aerostatic bearings. The machine is built but has not achieved its target speed due to the manufacture of the bearings. A detailed analysis is conducted according to the test results.