Electromagnetic Design and Analysis of a Novel Transmission System Supporting Multi-Path Power Flows for Electric Vehicles

This paper proposes a novel transmission system supporting multi-path power flows for electric vehicles (EVs). It mainly consists of a coaxial magnetic gear (CMG), a lock, a clutch, and two electric machines (EMs). The key feature of the CMG is that its modulating ring can rotate freely. One of the EMs is integrated with the CMG, which constitutes an integrated magnetic gear permanent magnet machine. And the other is connected to the inner rotor of the CMG through a clutch and a shaft with a lock. By toggling the clutch, controlling the states of the lock and the two EMs, the proposed transmission system can achieve flexible power splits. It is very interesting that one of the EM can play the role of a flywheel storage device when necessary, which is capable of buffering the energy from regenerative braking, so as to protect the battery. In this paper, the configuration of the transmission system is illustrated; its operating principle is elaborated. Then, the electromagnetic design is conducted to meet the demands arising from EVs. Finally, the electromagnetic performances are analyzed by using finite-element method, which verifies the rationality of the electromagnetic design.