Magnetic saturation impact on the steady-state operation of a controlled induction motor drive in rotor field orientation
Purpose - The purpose of this paper is to analyze the impact of magnetic saturation on the steady-state operation of the induction motor (IM) drive in regard to rotor field-oriented control (RFOC). The aim of the presented two methods is to obtain the required steady-state torque with minimal stator current, which thus reduces stator coper losses considerably. Design/methodology/approach - The first method is based on an analytic calculation of the peak torque-per-ampere ratio curve of saturated IM. The torque characteristics obtained at a constant stator current are used to calculate that value of magnetizing current which gives the minimal stator current for the required load torque. The second method directly searches the minimal stator current for the required load torque. Experiments completely confirm the efficiency of the proposed selection of a magnetizing current reference. Findings - Operation of the IM drive strongly depends on a proper selection of the rotor flux linkage reference value, the selection of which represents an additional degree of freedom in control design. Therefore, it can be used to optimize some of those drive features subjected to voltage and current constraints. The proposed calculation procedure is simple so that can be easily implemented in practically application. However, some additional IM data like magnetizing curve, inertia moment, and coefficient of viscous friction are necessary. Originality/value - The substantial impact of saturation on the stead-state torque characteristics of IM, determined for the constant stator current and the constant d-axis stator current, is determined analytically and numerically.
torque modelling electromagnetic induction electric current