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 ultrahigh speed applications due to the high windage friction. In this article, a novel ultrahigh 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 ultrahigh 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 r/min prevents the motor from reaching even higher speeds beyond 90 000 r/min. Some possible reasons are suggested to explain this interesting phenomena.