Kondo, K., Maekawa, T., and Kusase, S., "A New Multi Air Gap Motor with Trench Shaped Coil for HEV Applications," SAE Technical Paper 2014-01-1870, 2014, doi:10.4271/2014-01-1870.
This paper proposes a new multi air gap motor with trench-shaped coil. The proposed motor has high torque without rare earth magnets compared to conventional single air gap motors due to its multiple air gap and ferrite permanent magnet (PM) assisted segment rotor poles.Firstly, the basic structure and features of proposed motor is shown: three stator cores, integrated a set of three phase windings, and an annular rotor core with magnetic saliency at three sides and ferrite magnets. Then, the performance of proposed new motor and well-known single air gap IPMSM with rare earth magnet are compared by FEA.Secondly, the simple winding method similar to the conventional motor is clarified.Next, practical design of the 3-D magnetic circuit with laminated steel is discussed. Eddy current generated by the magnetic flux passing through the laminated steel in the core stacking direction is focused, and methods for reducing eddy current loss are shown.Finally, performances of proposed motor are verified by the prototype machine in test bench and actual vehicle. From these discussions, the possibility of low cost and high torque motor without rare earth magnets is shown.