Design of an active magnetic bearing system for a high-speed permanent magnet synchronous machine

Abstract

Currently, there are two high-speed permanent magnet synchronous machines (HS-PMSMs), nicknamed the TWINS, situated in the McTronX laboratory at the North-West University. However, excessive heat generated by the ball bearings of the motors causes the rotor to overheat. This could cause the permanent magnet on the rotor to demagnetize. The heat is generated by excessive friction caused by high-speed as well as improper alignment of the bearings. The main objective of this project is to develop an active magnetic bearing (AMB) system to replace the ball bearings of the TWINS with AMBs, in order to reduce the heat generated in the rotor. This is to allow the HS-PMSMs to be operated at a rated speed of 30,000 r/min. The secondary objective is to add knowledge and experience to the McTronX research group on AMBs. This project will focus on the design of the AMB system; including a feasibility study to replace the ball bearings with AMBs, the design of the electromagnets of the AMBs, as well as the retrofit that was done to the current HS-PMSMs to allow them to be operated on AMBs. Static tests will be done to confirm the design of the AMBs. However, the AMBs will only dynamically be tested in later projects as the rotor still need to be balanced, and the control of the HS-PMSM still need to be designed and implemented before the rotor can be operated at its rated speed.