Efficiency optimized control of induction machine drives for battery applications

Contemporary field oriented controlled induction machine drives constitute a good compromise between high power density and economical employment of exhaustible raw materials. Since for such drives the excitation is created by the magnetizing current which is part of the stator current along with the torque generating fraction, there are two degrees of freedom in the stator current generation to achieve a certain amount of torque. As for high integrated drives maximum efficiency is essential to reduce inverter heating to a minimum there arises the condition of a minimal stator current magnitude to torque ratio. The following article comprises a recipe for an analytical approach to an efficient induction machine stator current control. Influences of a saturated mutual inductance are taken into account to elaborate characteristic curves of magnetizing current versus torque to ensure minimal thermal stress on the inverter and thus compact design for induction machine servo drives especially applied for battery applications.