Use of canned rotors in high-field permanent magnet machines

The design of high speed permanent magnet machines needs to address conflicting requirements arising from the requirements of high electromechanical efficiency and mechanical strength and smoothness of running. The authors investigate the use of canning material surrounding the rotor, to give it mechanical strength, and investigate its consequences with regard to the electromagnetic performance of the motor at high speeds. Two designs are investigated in detail. The performance of a high-field magnet configuration is assessed experimentally, and compares well with the results predicted from finite-element computations