Design Considerations of Spoke-Array Brushless Dual-Electrical-Port Dual-Mechanical-Port Machine

Spoke-array brushless dual-electrical-port dual-mechanical-port (SA-DEP-DMP) machine is a good candidate for continuously variable transmission device, because of its high compactness, contactless torque transmission, and decoupled rotors. Due to the specific features, including two independent controllable rotors, two set windings, and complex magnetic field coupling, some unique design considerations of SA-DEP-DMP machine are analyzed in this article. First, there is a little accurate analytical model for DEP-DMP machine. An applicable analytical model is proposed to directly describe the characteristic of air-gap magnetic field and calculate the sizing equation. The key innovation is that the inner air-gap permeance with the slot effect is mapped into the magnetic potential by air-gap mapping model, which simplifies the double air-gap structure into a single air-gap structure. Second, the torques of two rotors are always optimized separately at the same time. Using this design method, the optimal torques of two rotors cannot achieve simultaneously for many parameters. In order to solve this problem, a novel constant torque ratio design method is proposed where two windings electric loading distributions are considered. The influences of key parameters, such as combination of slot and pole, stator split ratio, permanent magnet size, etc., on the torque performances are analyzed based on finite-element analysis. Finally, an SA-DEP-DMP prototype is manufactured.