Double stator switched reluctance machine with mutual coupled windings

Abstract

This thesis describes the development of a four-phase double-stator switched-reluctance motor (DSSRM) with mutually coupled windings. This machine, which has a topology that combines features of both the mutually coupled and double-stator switched-reluctance motor, will be shown to have the potential to offer improved torque productivity under the same ohmic loss limitation; though experimental mechanical and thermal confirmation remains to be completed. It is widely thought that the electrification of vehicle traction will be an essential element in the automotive industry in the next decade. An eventual sales ban on diesel and petrol vehicles has recently been reported to be planned by several industrial countries. Even disregarding these political declarations, which could only be considered as expectation rather than strict policy, the spread of hybrid powertrain technology and the continuous fall of Li-ion battery prices will effectively motivate an increasing number of automotive manufacturers to participate in this revolution. Since the cost of rare-earth materials is expected to continuously rise and the mining of these resources has left an enormous impact on the environment, the development of a high-performance SRM as an alternative to a permanent magnet synchronous machine (PMSM) is worthy and necessary. In addition to the enhancement of electromagnetic performance, this thesis discusses the mechanical properties and rotor structure of the DSSRM. The rotor support, which holds the rotor segments together, should be strictly of non-conducting material to prevent significant eddy current loss. Since most materials struggle to offer a compatible stiffness to steel, methods have been investigated to meet the challenge of designing a rotor support able to endure the centrifugal force of rotor segments during high-speed spinning. Thermal issues pose another challenge for this prototype but simulations indicate that the DSSRM could have better cooling capability than the conventional SRM configuration. A prototype was built and compared with a 12/16 segmental-rotor SRM, previously developed at Newcastle University. The results indicated that the prototype machine gave a promising torque performance with a relatively low copper loss.