Unified Analytical Modeling of Armature Magnetic Field of Slotless PM Motor With Equidirectional Toroidal Winding

This article proposes a unified analytical model (AM) for the armature magnetic field (AMF) of slotless permanent magnet (PM) motors with equidirectional toroidal winding (ETW). The AM is based on the magnetic field generated by the active side conductors of ETW single-phase coils. It not only can clarify the operating mechanism of ETW AMF in the theory and quantitatively analyze its AMFs and inductance, but also reveals the characteristics that distinguish ETW inductance analysis from other windings. In addition, it can serve as the cornerstone for analyzing the AMF of other windings. First, the structural parameters unified principle of different slotless PM motors with ETW is proposed. Second, based on the principle, the unified AM of AMF generated by the active side conductors and inductance of ETW single-phase coils are established and verified by the finite-element model. Finally, a prototype of a dual rotor slotless axial flux PM motor with ETW is manufactured, and the armature magnetic density waveforms under single-phase and three-phase excitation conditions and the inductance of ETW are tested, which verifies the accuracy of the proposed AM.