A New Magnetic Field Modulation Type of Brushless Double-Fed Machine

In this paper, a new magnetic field modulation type of brushless double-fed (MFM-BDF) machine is proposed, in which a split-pole structure inner stator with three modulating poles on each stator tooth and an outer rotor with surface-mounted permanent magnets are adopted. By employing a set of 3-phase armature winding and a set of 3-phase field winding wound around stator teeth and modulating poles, respectively, the hybrid excitation operation can be achieved. The proposed machine can achieve not only a high torque density due to the magnetic field modulation effect, but also an wide operation region and an almost unchanged cogging torque peak-to-peak value by feeding flux-weakening and flux-enhancing currents into the field windings, respectively. The configuration of proposed machine and the basic principle are introduced first. Then by using 2-dimension finite element analysis, the basic characteristics, such as no-load flux linkage, cogging torque and no-load EMF are analyzed.