Experiment Study on a High Speed Motor Supported by Active Magnetic Bearings

In a high speed motor system suspended by active magnetic bearings, the bearing load capability is limited, the bias force from the motor rotor produced by permanent magnets is large compared with the bearing load capability and the influence of the residual unbalance in the rotor is obvious. So the active magnetic bearings have to work with nonlinearity conditions and high speed running is hard to be achieved. To deal with the marked nonlinearity of the active magnetic bearing system, a global linearization method is used to linearize the magnetic forces produced by active magnetic bearings. Meanwhile, controller designs are improved. A gain schedule method is used to make the rotor running stable across its rigid critical speed. Through using a zero-pole pair shaping method, the gain of the controller in the frequency domain near the running frequency of the rotor is effectively decreased and the rotor runs almost about its mass centre. The saturation of the magnetic forces of the active magnetic bearings is avoided and stable running of the motor system at high rotation speeds is achieved.