Design of a High Speed Switched Reluctance Machine for Automotive Turbo-Generator Applications

Abstract

The efficient generation of relatively large quantities of electrical energy in vehicles is becoming an increasingly important issue, as a result of increasing demands of ancillary equipment and the emergence of hybrid power-train vehicles. An attractive solution to meeting these demands is to extract the electrical energy by means of a generator driven by a high-speed exhaust mounted turbine, a technology that is beginning to emerge commercially. This thesis is concerned with the design of a system, which extends this concept to enable both electrical generation and highly flexible air-management. The heart of the system is a high-speed switched reluctance machine, the rotor of which is located on a common shaft with the turbine and compressor wheels of a standard commercial turbocharger. The design synthesis of a -switched reluctance machine capable of meeting the required performance specification is particularly onerous given the harsh environment in which it operates, specifically in terms of the restricted space envelope, the high ambient temperature and the very high rotational speeds. This thesis describes the design of a switched reluctance machine for a prototype system, a procedure that encompasses the detailed analysis of centrifugal stress in the rotor, aerodynamic losses, iron loss, rotordynainic performance and dynamic performance. The design and analysis of the system is supported by experimental evaluation at both component and system level.