SiC Based Switch-Mode Power Amplifier for Active Magnetic Bearing

Active Magnetic Bearing (AMB) is an electromagnetic system that supports the rotor of high-speed rotating machinery in a contactless manner through magnetic forces. Excitation coils of an AMB are fed from current-controlled power electronic converters for high-bandwidth closed-loop control of the radial forces on the rotor. This paper presents the design, fabrication, and testing of an SiC-based switched-mode power amplifier for feeding the excitation coil of an AMB. The scope includes determination of converter ratings, device selection, other component selection, PCB layout and testing. The converter ratings are determined based on the design of AMB and an estimate of the residual mass unbalance in the high-speed rotor to be supported. Device losses are compared for the Si and SiC based devices considered. Converter design based on SiC devices is discussed. Experimental results pertaining to double-pulse test, load test and current reference tracking are presented.