Derivation of a Lorentz force generation model on Bearingless surface-mounted PM synchronous motors

This paper presents the Lorentz force generation model for bearingless Surface-mounted PM Synchronous motors. The Lorentz force varies according to the different combination of pole numbers of the motor windings and the suspension windings of bearingless motor. The mathematical model of bearingless motors with generalized pole number are analyzed. The derived models are compared with FEM simulation using the bearingless motor models with the combination of 2-pole motor and 4-pole suspension windings, 4-pole motor and 2-pole suspension windings, 4-pole motor and 6-pole suspension windings, 6-pole and 4-pole bearingless motors. The analytical model and FEM simulation agree mostly in the y-direction, however, more than 10% error appears in x-direction. From result of the additional investigation, it is considered that the cause of the analytical calculation error is the effect of the reflective magnetic field by the eddy current.