Toroidal Field Excitation for Axial-Field Double-Rotor Flux-Reversal DC Motors With Magnetic Differential

In order to provide differential action for electric vehicles (EVs) performing reliable cornering, the axial-field (AF) double-rotor (DR) flux reversal (FR) motor shows a good ability of torque output along with magnetic differential (MagD) control on its two rotors. Apart from using the permanent magnet (PM) excitation, which suffers from high PM cost and risk of accidental demagnetization, this article proposes toroidal dc (TDC) windings for field excitation to avoid the problems associated with PMs. The TDC windings not only serve as the source of the magnetic field but also regulate the flux on two rotors to produce MagD action. By using 3-D finite-element analysis, motor performances between using the TDC windings and the conventional concentrated dc (CDC) windings are quantitatively compared, which validates that the proposed AF-DR-FR-TDC motor takes definite advantages over the CDC counterpart while offering the desired MagD action.