Highly efficient approach to the simulation of variable-speed induction motor drives

Loss modelling for induction machines operated as variable speed drives (VSD) is indispensable for designing highly utilised traction machines. Accurate loss modelling can be performed using finite-element analysis (FEA). Since VSD have to deliver torque at different values of mechanical speed, the torque-speed operating points are sought. For those torque-speed operating points, the drive should be operated in the highest efficiency points. Finding these points from transient FEA requires the simulation of several ten to hundreds operating points in terms of stator current and rotor fundamental frequency. For that reasons, local loss modelling using FEA is very time consuming. This study will present a hybrid simulation approach coupling numerical and analytical models to reduce simulation time for simulation of the torque-speed operating points. The simulation approach takes into account the inverter voltage and current limitations and finds the highest efficiency operating point for every torque-speed operating point.