Analytical Calculation Model of an Induction Machine with Combined Star-Δ Windings Taking into Account Multiple Armature Reaction and Slotting

Abstract:
An analytical calculation model for induction machines with combined star-δ windings and squirrel cage rotors is presented. The model makes it possible to calculate the steady-state behaviour and several parasitic effects of these machines. Based on an assumed unsymmetrical phase system, the magnetomotive force of the stator and the rotor can be calculated. Here, thread-like surface currents are presumed. The flux density in the air-gap is modulated by permeance waves to account for stator and rotor slotting. The multiple armature reaction enables to determine current harmonics in the stator and rotor except of saturation harmonics. This allows to establish several torque components via a method of virtual displacement. The analytical calculation model is compared to transient finite element method (FEM) results for verification purposes. It is to mention that the presented analytical calculation model also allows to calculate regular six-phase induction machines.