Fault tolerant magnetic bearings

A fault tolerant magnetic bearing system was developed and demonstrated on a large flexible-rotor test rig. The bearing system comprises a high speed, fault tolerant digital controller, three high capacity radial magnetic bea rings, one thrust bearing, conventional variable reluctance position sensor s, and an array of commercial switching amplifiers. Controller fault tolera nce is achieved through a very high speed voting mechanism which implements triple modular redundancy with a powered spare CPR, thereby permitting fai lure of up to three CPU modules without system failure. Amplifier/cabling/c oil fault tolerance is achieved by using a separate power amplifier for eac h bearing coil and permitting amplifier reconfiguration by the controller u pon detection of faults. This allows hot replacement of failed amplifiers w ithout any system degradation and without providing any excess amplifier kV A capacity over the nominal system requirement. Implemented on a large (244 0 mm in length) flexible rotor, the system shows excellent rejection of fau lts including the failure of three CPUs as well as failure of two adjacent amplifiers (or cabling) controlling an entire stator quadrant.