Feedback control of a novel bearingless torque motor using an extended FOC method for PMSMs

In recent years, industrial demand for magnetically supported direct drives which operate without contact and feature high torque capacity has been growing. We present a novel design solution for a bearingless torque motor. The proposed configuration has a six-phase winding with concentrated coils in double star connection to minimize power electronics efforts. The six-phase winding system generates simultaneously both the actively controlled motor torque and the radial bearing forces for radial position control. The disk-shaped hollow shaft rotor carries 26 permanent magnets. To reduce system costs, tilting deflection and axial position of the rotor are stabilized passively by magnetic reluctance forces. We describe the mathematical model and an appropriate control for current and voltage drivers. Finally, we present a prototype motor.