Performance characteristics and parameter identification for inset type permanent magnet bearingless motor drive

A precise measurement of parameters and its effectiveness on the suspension performance has been verified in an inset type permanent magnet (PM) bearingless motor drive. A set of three-phase windings are inserted in the stator slots of the motor for suspension force generation in order to act us a bearingless drive. In the proposed method, suspension force parameters can be identified without magnetic suspension. Induced voltages at suspension winding terminals are measured as a function of rotor radial displacements, while a shaft is supported by mechanical bearings. The estimated values of parameters are compared to those obtained from measurement during magnetic suspension. The proposed parameter measurement is found to provide suspension parameters within acceptable tolerance range, while ensuring stable magnetic suspension. Load torque tests have been successfully carried out during magnetic suspension. There exists good agreement between the predicted and measured performance results for a prototype experimental inset type bearingless PM motor.