A Novel Counter-Rotating Single-Stator Dual- Internal-Rotor Permanent Magnet Machine

This article proposes a novel counter-rotating single-stator dual-internal-rotor permanent magnet (CSDPM) machine. This machine utilizes magnetic field modulation in the fractional slot concentrated winding permanent magnet (PM) and vernier PM (VPM) machines to realize the counter-rotating (CR) operation for some special applications, such as underwater vehicles, wind power turbines, household appliances, and so on. This machine has only one set of stator armature winding with easy manufacturing and robust structure, which greatly reduces the cost, weight, and space requirement compared with the conventional CR system. The magnetic field modulation principle and the relationship between two rotors and the armature reaction are analyzed. The electromagnetic performance of the CSDPM machine is comprehensively investigated. It shows that the proposed CR system with the CSDPM machine has higher torque than the conventional CR system by using two single-rotor PM machines. There is no magnetic coupling effect between the two rotors in the CSDPM machine. The torque split of two rotors can be easily changed with the corresponding rotor stack length. The results are validated by experiments on a prototype CSDPM machine.