Analytical Model of The Magnetic Field in Doubly Slotted Electrical Machines With Distributed Windings and Evaluation of E.M.F. and Torque

The quantities of interest in an electrical machine (e.m.f. and torque) can be evaluated once known the air-gap flux density. The paper shows how to analytically model this flux density distribution, as a function of time and of the rotor position, considering the actual disposition of slots and conductors and the geometrical characteristics of the air-gap periphery. The winding m.m.f. is evaluated by summing suited step functions; as regards the slots, specific field notch functions are obtained, by analytical field solutions and applying suited superposition techniques. The method is applied to constant air-gap machines, neglecting magnetic saturation. Some e.m.f. and torque evaluations are shown and discussed.