Rotational Test of Flexible Rotor Supported by Active Magnetic Bearings (1st Report, Passing the 2nd Bending Critical Speed)

Abstract

In recent years, Active Magnetic Bearings (AMBs) characterized by non-contact support without mechanical loss have been applied in industrial turbo rotors. In relation to growth of AMB market, corresponding ISO standards are developed for public users. The purpose of this research is to demonstrate a usage of high speed rotation up to the 3rd bending critical speed in the flexible rotor supported by AMBs. In this paper, we explain about the following three topics : (1) an improvement of motor driving unit from direct drive to non-contact drive using a flat motor ; (2) a modification of the AMB controller from analog to digital types; (3) a flexible rotor balancing method, called modal balancing, is experimentally demonstrated using 5 planes totally. The feature of this balancing is effective only to a target mode with no influence to other modes. Finally, we tested successfully the pass of the second bending critical speed and the smooth rotation around the third bending mode at rated speed (250 rps).