Soft magnetic composites in active magnetic bearings

Active magnetic bearings are being considered increasingly for high-speed electrical machines, since they eliminate frictional losses and are virtually maintenance-free. However, in addition to the copper loss in the coils, there may be a significant eddy current and hysteresis loss in the soft magnetic rotor. These can be minimised by an appropriate choice of rotor material and bearing topology, whilst the use of nonlinear control can also assist in reducing the total loss. The example of an energy storage flywheel using a PM motor/generator is discussed