Different arrangements for dual-rotor dual-output radial-flux motors

This paper describes different arrangements for a dual-rotor, radial-flux, permanent-magnet brushless DC motor for application to variable-speed air conditioners. In conventional air conditioners, two motors of appropriate ratings are usually used to drive the condenser and evaporator separately. Alternatively, a motor with outputs on both sides of a common shaft may be employed and this is studied here. The motor has an inner and outer rotor with a stator in between which is toroidally-wound or axially-wound with inner and outer slotted stator surfaces. The power sharing on the two rotors is designed to meet the requirement of the condenser and evaporator. 3D time-stepped finite element analysis (FEA) is employed (JMAG) to verify the designs. A prototype is made and tested to evaluate the performance. Alternative windings are investigated to assess the possibilities of decoupling the rotors so that they run independently. In the final section a new and novel arrangement is described where one toriodal 3-phase winding set is used to control two rotors, one inner and one outer, of different pole number. The design is tested using FEA solutions and the initial results indicate that this machine could operate successfully.