Experimental Measurement of Rotational Losses in Magnetic Bearings

Rotational losses in magnetic bearings are studied experimentally. The experimental setup was a totally active magnetic bearing system of vertical type. It had an axial bearing and two radial bearings. The radial magnetic bearing had eight poles. The arrangement of the magnetic poles was alternating pole arrangement (NSNSNSNS) or paired pole arrangement (NNSSNNSS). The rotor was also one of the two types: laminated and solid (non-laminated). Rotational losses were estimated from run- down tests. Measurements were performed in a vacuum chamber. The experiments showed that (i)effects of pole arrangement for the laminated rotor were small, (ii)the rotational loss of the solid rotor wa'> five to sixteen times larger than that of the laminated rotor, and (iii)the rotational loss in the paired pole arrangement was about 1.2 times larger than that in the alternating pole arrangement when the solid rotor was used.