Analysis of a Spoke-Array Brushless Dual-Electrical-Port Dual-Mechanical-Port Machine With Reluctance Rotor

A novel brushless dual-electrical-port dual-mechanical-port (BLDD) machine, with spoke-array permanent magnet (PM) outer rotor and reluctance inner rotor is proposed in this article. The BLDD machine can be regarded as the combination of the flux modulation machine and PM synchronous machine (PMSM). Compared to the existing BLDD machine, the PMs of the proposed machine only insert into the outer rotor, hence both torques in two machines can reach their optimal values at the same time. Moreover, the spoke-array PMs with inherent flux-focusing effect can reduce the effective air-gap length of PMSM portion and improve the working flux density, thus increasing the torque density significantly. Besides, the reluctance inner rotor without magnets has the advantages of simple structure and high reliability. The structure and operation principle are introduced. Then, the influences of main parameters including slot/pole combination, split ratio, PM size on torque performance are studied. Next, the proposed BLDD PM machine is compared with the conventional one in terms of air-gap flux density, back electromotive force, magnetic forces, and torque performances. A prototype and test bed are designed and built, and the experimental results verify the analysis results.