Analytical Computation of the Electromagnetic Torque in Doubly Slotted Synchronous Machines with Distributed Windings

An accurate, analytical computation of the electromagnetic torque waveform in isotropic synchronous machines is developed, by employing a suited analytical field model. To this aim, the stored co-energy in the airgap volume, due to all the m.m.f.s is evaluated, as a function of time and rotor position, subsequently obtaining the torque components, by performing the co-energy derivative: the method, for now limited to unsaturated conditions, takes into account the actual winding features (field N° of slots/pole; armature N° of layers, N° of slots/(pole×phase), coil pitch), as like as the air-gap core geometry (air-gap and slot opening widths). Some comparisons among analytical and FEM simulations have been performed, obtaining very good agreement.