A novel numerical method for accelerating the computation of the steady-state in induction machines

This paper presents a novel and efficient methodology to reduce the time needed to reach the steady-state in the finite element simulation of induction machines. More precisely, the work focuses on induction motors with squirrel cage rotor, where sources in the stator coil sides are given in terms of periodic currents. Essentially, the procedure consists in computing suitable initial conditions for the currents in the rotor bars, thus allowing to obtain the steady-state fields of the machine by solving a transient magnetic model in just a few revolutions. Firstly, the mathematical model that simulates the behavior of the machine is introduced. Then, an approximation of this model is developed, from which suitable initial currents are derived by computing the solution in the least-square sense to an overdetermined problem with only two unknowns. Finally, the method is applied to a particular induction machine working under different operating conditions. The results show important computational savings to reach the motor steady-state in comparison with assuming zero initial conditions, which validate the efficiency of the procedure.This work has been partially supported by Robert Bosch GmbH, Spain under contract ITMATI-C31-2015, by FEDER and Xunta de Galicia (Spain) under grant GI-1563 ED431C 2017/60, by FEDER/Ministerio de Ciencia, Innovación y Universidades-Agencia Estatal de Investigación, Spain under the research project MTM2017-86459-R, and by Ministerio de Educación, Cultura y Deporte (Spain) under grant FPU13/03409. The authors express their gratitude to Dr Marcus Alexander and Dr Stefan Kurz from Robert Bosch GmbH for useful discussions about induction machines and for providing us with the data for the numerical experiments.S