An improved 2D subdomain model of squirrel cage induction machine including winding and slotting harmonics at steady state
Résumé
This paper proposes an improved subdomain model of squirrel cage induction machines with imposed stator currents. This new model enables to accurately compute electromagnetic quantities such as air gap flux density, instantaneous torque and forces, electromotive force including all harmonic content. The first improvement is to explicitly account for rotor motion with time-stepping technique. The second improvement consists in modelling the skin effect in rotor bars by considering each space harmonic of the stator magnetomotive force separately. Eddy-currents in rotor bars are therefore " skin-limited " and not " resistance-limited ". The results are then validated with linear transient finite element analysis for both no-load and load cases, taking a topology of squirrel cage machine already used in previous references. The time and spatial harmonic content of all electromagnetic quantities is also validated by comparison with analytical expressions. The computation time is a hundred times lower than finite element as it does not require achieving a numerical transient first and the resolution for a time step is shorter. Thanks to its computational efficiency and intrinsic mesh insensitivity, this method is particularly suited to magnetic forces computation and vibroacoustic analysis of squirrel cage induction machines.
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