Gap Modulation of Concentrated-Winding Permanent Magnet Motor and Clarification of Theoretical Turning Point against Distributed Winding

Abstract

By focusing on the gap modulation of concentrated-winding permanent magnet (PM) motors, the superior/inferior branch point between concentrated and distributed windings was clarified. It was found through novel theoretical formulae considering the gap modulation effect that distributed-winding PM motors have about 10% larger q-axis inductance than concentrated-winding motors, which leads to a decrease in the high-speed operation range. Furthermore, the difference in reluctance-torque contribution between the two winding types was theoretically quantified. These findings enable motor designers to easily judge a superior winding type during the initial design stage. By applying the above-mentioned method to a 0.2kW concentrated-winding Nd-Fe-B magnet motor, it was possible to quantify the minimum core stack length of the distributed-winding motors to satisfy the required maximum load without relying on finite element analysis (FEA) and using only the introduced theoretical formulae. The validity of the proposed approach was demonstrated by the FEA and measurements of the designed distributed-winding PM motor.