Study of High-Performance Vector Controls for AC Servo Motors Taking Core-Losses into Account

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The following results are obtained through the study.1) A unified mathematical model for AC motors is newly established, which succeeds in modeling eddy current and hysteresis losses of stator separately and simultaneously.2) Mathematical models for stator flux of induction and synchronous motors are also established. It is shown that concrete models for induction or synchronous motor can be easily obtained by applying the stator flux models to the unified model.3) It is shown that the above results defined on two dimensional orthogonal coordinates can be extended to the U, V, W three phase coordinates.4) As well known, block diagrams are useful for overall comprehension. Simple and clear block diagrams of AC motors are newly established, which use vector signals rather than scalar signals. The block diagrams succeed in expressing the core loss phenomena caused by eddy current or/and hysteresis loss and have a high generality.5) A new identification method is established, which can identify equivalent core-loss resistances on the unified mathematical model corresponding to eddy current or/and hysteresis loss. The usefulness of the identification method is verified through experiments using three motors.6) A vector control method taking core-losses into account is established, which can be applied to synchronous motor as well as induction motor.7) A minimum loss strategy associated with vector control taking core-losses into account is established for induction motor.8) The above results are applied to sensorless induction motor drive especially for electric vehicle and its usefulness is confirmed.