Analysis of the segmented displaced trapezoidal winding for force and torque production as a self bearing motor

Self bearing motors have been identified as a potential technology for oil free turbomachinery where integral starter generator (ISG) technology may be used, among others. One of the key advantages of self bearing motors is that they reduce the shaft length of machines, hence increasing the rotordynamic performance. Until now, research has yielded self bearing motors that produce motoring torque and active force control of either the radial forces or the thrust force. In this paper, a new self bearing motor winding is analyzed for its potential to simultaneously produce actively controlled torque, radial forces and thrust force. The benefit of such a design is that the shaft length can be reduced even further as both the radial bearing and thrust bearing functions are performed by the motor. Experimental results are presented that verify the force and torque production capability of the motor to within 14% of the theoretical predictions. Another benefit of the motor is its ability to be used for large axial (thrust) movements, such that it could be used in precision axial positioning of high speed rotating loads over a large range (up to 25 mm or so for a 25 mm diameter rotor).