On accuracy of loss models including VSD induced additional harmonic losses for online energy efficient control of induction motor

Energy efficient control of induction motor involves representation of motor losses by a suitable models in control structure and generation of control reference such that modelled losses are minimized. Accurate loss representation thus form an important part of loss model based (LMC) control. This paper deals with subject of loss model accuracy versus complexity of online implementation of such models for online maximum efficiency control. It is shown in this paper that the additional harmonic losses and stray losses can be conveniently neglected in loss models without deteriorating the accuracy of such control. To prove the above point, the induction motor losses are measured through no load and load tests and then are segregated into different loss components. The modelled losses are then compared against measurements to establish accuracy of different models. Then a reduced complexity model is proposed in this paper, which is much simpler to be used in online loss model based control and the parameters required for this model can be easily obtained through online identification procedures. The deviation of optimal flux reference for LMC control using reduced loss model is analyzed and it is shown that the optimal flux reference for minimum loss operation does not change even after neglecting additional harmonic and stray load losses for most of the operating load conditions.