Minimum Copper Loss Control Strategy for dc-biased Vernier Reluctance Machines based on Speed Variation

A minimum copper loss control strategy for dc-biased vernier reluctance machines (dc-biased-VRMs) based on speed variation is proposed in this paper. The novel dc-biased VRM uses the unique armature current of sinusoidal with dc bias. The dc bias component generates the rotor flux and the sinusoidal component generates the stator flux. The copper loss produced by the dc bias current is independent with the motor speed, but the copper loss produced by the ac component increase with current frequency, which is mainly due to the skin effect and proximity effect of the conductor. By using finite element analysis (FEA), the ac copper loss variation with ac current and rotational speed is analyzed. Then, the current distribution that producing the minimum copper loss with the given torque is solved using Lagrange method. Besides, the inductance nonlinearity is also taken into considered by constructing the inductance table. Finally, the total copper loss can be minimized by improving the dc bias component in armature current with the increment of rotational speed. The simulation results verified the effectiveness of the proposed method.