Study On Active Magnetic Bearing System Of High Power Motor And Its Application

The magnetic bearing, a typical electromechanical device related to rotor dynamics, mechanics, control engineering, electromagnetics, electronics and computer science, is a novel type, high performance bearing, which suspends the rotor by controlled magnetic force without any mechanical contact between rotor and stator. It has been noticed widely and researched in the fields of science and industry since 1960s, for its advantages such as contact-free, no lubrication, no wear, low noise, high rotation speed and long-life, etc.In this thesis, the principle, structure, research status, difficulties and trend in industry applications of active magnetic bearing (AMB) are introduced first. The AMB system for high power motor is studied on the background of Helium circulator in gas-cooled reactor and Fly-wheel energy storage system.Secondly, A set of improved AMB for 15kW motor, safety operation scheme are designed. and monitor system for remote measure, adjust and control of the parameters. A novel structure of AMB is proposed to eliminate coupling between magnets with non-magnetic material, reduce reluctance and power consumption and increase efficiency. The effect of eddy current on AMB's performance is calculated. Accordingly, a structure of axial magnetic flux is proposed to reduce effect of eddy current in solid rotor.Thirdly, several typical characteristics of AMB such as the differential control, the measure mode of sensor, the treatment of difference between sensor and electromagnetic force action point, the effect of axial trust plate's slope on radial bearing, the control strategy of power amplifier, the influence of gyroscope effect and imbalance magnetic force of motor on bearing system have been analyzed. According to mathematical model of AMB and the nonlinear characteristics of suspension system, a nonlinear PID control arithmetic with across feedback compensation for gyroscope effect and mass offset compensation based on notch filter is adopted to increase control precision.Finally, A lot of simulation data and experiment results analyses of four typical situations for the test motor with AMB have been made, and many conclusions about application are obtained. With detailed theoretical analyses and experiments, the performance, key technology and industry application of high power, high rotation speed motor system supported by AMB are discussed in the thesis. The six-freedom-degree stability control of rotor is realized in experimental motor. It shows the availability and rationality of system design and solutions.