PM brushless motor design for helicopter tail rotor

This paper presents the design of multi-phase permanent magnet brushless motor for an electrical helicopter tail rotor. The design should guarantee a high reliability because the tail rotor is a safety critical system and should match a given envelope to allow a substitution of the actual mechanisms. In order to obtain high torque maintaining small overall dimensions of the motor, a spoke-type solution with interior PMs has been chosen. The motor performance has been evaluated by the FE analysis in the healthy and faulty mode operations: the performance fully satisfy the requirements at low and high power. The study has been completed with a detailed thermal analysis in order to calculate the temperature in the stator winding and PMs at steady-state imposing the severe duty cycle.