Ultra-high Speed Switched Reluctance Machines Research Articles

Design and Experimental Analysis of an Ultra-High Speed Switched Reluctance Machine With Aerostatic Bearings

High-speed electric machines have become a hot research topic in recent years. Switched reluctance machines (SRMs) are good candidates for high speed applications due to their simple rotor structure without magnets. However, the double-salient structure of conventional SRM rotors are not suitable for ultra-high speed applications due to the high windage friction. In this paper, a novel ultra-high speed SRM is proposed using a solid cylindrical rotor. A detailed electromagnetic design of dimension calculation, air-gap calculation, material selection, winding selection, windage torque calculation, drive system and control strategy are presented. A closed loop control model is built using Maxwell/Simplorer co-simulation to estimate the performance of the machine. Then, in order to explore the feasibility of using other types of bearings for SRMs than ball bearings at ultra-high speeds, the machine is prototyped and integrated with aerostatic bearings. Detailed experimental results are presented. The measured inductance and current profiles match the design value well. However, the unexpected large windage friction beyond 40,000 rpm prevents the motor from reaching even higher speeds beyond 90,000 rpm. Some possible reasons are suggested to explain this interesting phenomena.

High-Strength Rotor Design for Ultra-High Speed Switched Reluctance Machines

High speed machines are gaining popularity in more and more applications. Besides permanent magnet (PM) machines, switched reluctance machines (SRMs) are very competitive candidates for high-speed applications in high-temperature environments due to their single material rotor without PMs. However, the conventional rotor geometries of SRMs are not suitable for the ultra-high speed applications. In this article, a novel high-strength, high-torque-density, high-efficiency rotor design for the ultra-high speed SRMs is proposed. First, a three-dimensional finite-element analysis is conducted to calculate the von-Mises stress distribution of the proposed rotor and shaft. Then, in order to improve the bonding and robustness of the design, proper high-strength adhesives are used and modeled based on the cohesive zone model. A parametric study is conducted to find the optimal length of the rotor stack. A thermal stress case study is also conducted. Finally, several prototypes are built to validate the manufacturing feasibility of the proposed design.