A Novel Design Method for the Electrical Machines With Biased DC Excitation Flux Linkage

A novel design method for electrical machines with biased dc excitation flux linkage, named biased flux machines (BFMs) is proposed in this paper. The biased current including dc and ac components is applied to drive these machines, in which dc current is used to generate or modulate the exciting magnetic field and ac current is used to generate armature field. To demonstrate this design and control method, a new double salient BFM is proposed. The feasibility of this design is verified by simulations and experiments. The major advantages for this design method could be summarized as: 1) for permanent magnet exciting BFMs, the biased current can be combined with negative d-axis current to realize flexible flux weakening or strengthening control; 2) for hybrid exciting or electrical exciting machines, the biased current can function as the dc windings, which helps to save more space for armature windings and further reduce cost and improve efficiency; and 3) this method is universal, which can be used in all BFMs.