Optimum Compensator Design for the Flexible Rotor in Magnetically Suspended Motor to Pass the First Bending Critical Speed

This paper proposes a phase compensator design for the flexible rotor in the high-energy-density magnetically suspended motor (HEDMSM), whose rated rotational speed is above the first bending critical speed. The optimum phase and magnitude of the control system nearby the critical speed are analyzed. Additionally, the coil inductance of the large-power HEDMSM is always large. That will lead to large phase lag and make optimum compensator design more difficult. Therefore, an effective phase-leading compensation method is presented to compensate the large phase lag of the switching power amplifier. Then, the optimum compensator is designed and carried out in the 315-kW HEDMSM. The experimental results show that the optimum compensator can minimize the displacement resonance peak, when the rotor passes the first bending critical speed with low amplifier current.