Abstract
Background: The paper deals with the modelling of a traction Linear Induction Motor (LIM) for public transportation. Typical problems arising from the electromagnetic finite element model development are described. The end effect causes asymmetry of phase impedances of the LIM. Because of that, if the LIM is supplied from the voltage inverter, which is usually the case, the phase currents become asymmetric. This causes performance calculation discrepancies in models that assume phase current symmetry.
Aim: The aim of the paper is to develop a method for calculating the imbalanced three-phase LIM currents to precisely predict the LIM performance.
Methods: Here, a method is developed to calculate the LIM phase current asymmetry by means of a self-developed electromagnetic finite element program – ELMAG, capable of adapting mesh generation based on Reynolds, Péclet and skin-depth numbers.
Results: The calculated asymmetric currents are used in a real size traction LIM calculation in COMSOL, to derive the performance characteristics for comparison with the results achieved when supplying the LLIM with the symmetric three phase current.
Conclusion: These results show that the natural asymmetry of the currents is an important factor that must be considered in appropriately calculating the LIM performance.