Suspension Principle and Digital Control for Bearingless Permanent Magnet Slice Motors

As bearingless motors have all advantages of magnetic bearings, they play an important role in solving difficult problems of special electric drives. The simplest and most versatile form of bearingless motor is the bearingless slice rotor motor. This kind of motor with centrifugal pump has a wide range of applications in life science, chemical processing industry, semiconductor manufacturing industry, foodstuff processing industry, and so on. In the paper, a 3-phase permanent magnet slice rotor motor is set up, and suspension principle of bearingless permanent magnet slice rotor motors is introduced. Theoretical formulas of driving system and radial suspension forces are given, and then the control system for the 3-phase bearingless permanent magnet slice rotor motor is designed and presented. An experimental platform of digital control system is developed to meet the need, and experiments including core loss measure, speed regulation and suspension force control are performed. The experiment results are presented under unload and load. The experiments have shown that the vibration amplitude in x- and y-direction is less than 200 mum under unload and load, while rotor speed are changed from 0 r/min to 8000 r/min