A design procedure for a PM machine with extended field weakening capability

A design procedure for the consequent pole permanent magnet (CPPM) machine is presented. Due to its double excitation nature (PM and field winding) and inherent three-dimensional flux distribution, an appropriate set of equations must be derived to model its magnetic structure. For practical operating conditions, radial, axial and tangential flux components are present. Therefore a convenient representation of the magnetic sources and their magnetic paths are necessary. For this purpose, a simplified reluctance-based equivalent circuit for 2-poles is developed to capture the main features of the machine. Approximated expressions for the airgap flux and the airgap flux density are derived. In these expressions the constant contribution of the PM and the variable flux provided by the field winding are taken into account. In addition, a formulation to calculate AC and DC slot geometry, copper and iron losses estimation and output power are developed. Finally, an optimization procedure is outlined based on maximum material utilization under current and magnetic loading constraints.