New types of oil free Helium refrigerators, using centrifugal compressors are now under development to cool the superconducting electric power generators. Because of their low efficiency, not much attention has been paid to regenerative compressors up to now. But, their compression characteristics, for example, higher pressure ratio and no surging vibrations, are desirable for Helium refrigerators which require perfect reliability for cooling practical superconducting machines. This report describes the merits expected by adaption of regenerative compressors to new type Helium refrigerators, construction of the trial compressor equipped with 5-axis controlled magnetic bearings and results of the basic test operation of the magnetic bearings.
