Electrical machines fitted with glacier magnetic bearings

Active magnetic bearings using the principal of controlled DC electromagnetic suspension have been available to machinery designers for over 20 years. The maturation of this technology has coincided with a trend towards higher speed and wider operating envelopes on many classes of machine. The combination of these two factors has resulted in the acceptance of their use within a wide range of high speed rotating machinery applications, in particular where conventional bearing solutions may be limited or no longer cost-effective. Magnetic bearings have found application and been designed for use within electrical machines ranging in size from a few kW to 23 MW and speeds up to 40,000 RPM. This paper discusses the range of electrical machines which have been fitted with magnetic bearings and the motivations for using magnetic bearings in such applications. An analysis of the losses in the the magnetic bearings is presented together with experimental results from the applications presented.