Optimal design of rotor circuits in induction type bearingless motors

A design procedure of optimal rotor circuits is proposed considering a thickness of divided coil end conductors. If the conductor thickness is increased, rotor bar length is also increased, which results in an increased secondary rotor resistance. On the contrary, if the conductor thickness is decreased, a significant resistance is caused in coil end circuits, which also results in the increased secondary resistance. It is shown that there is an optimal design point to minimize the secondary resistance. The optimal design point is analytically derived. Test results indicated a validity of the proposed optimal design procedure.