Determination of the optimal slip value for minimizing electrical losses in an induction motor
DOI:
https://doi.org/10.15588/1607-6761-2026-1-5Keywords:
induction motor, minimization, slip, steady-state operation, energy efficiency, electrical lossesAbstract
Purpose. The aim of the work is to conduct theoretical research and develop a methodology for determining the optimal operating slip value to minimize electrical losses under varying load conditions on the induction motor rotor shaft.
Methodology. The research was conducted using the fundamentals of mathematical modeling theory for a generalized AC electrical machine, classical optimization methods, the basics of automated control theory, loss minimization techniques in induction motor drives, and methods for the interpolation and approximation of calculated data.
Findings. A methodology has been developed for determining the optimal operating slip value to minimize electrical losses under varying rotor shaft load conditions in a quasi-steady-state mode of induction motor operation. A universal objective function for minimizing electrical losses in the induction motor as a function of slip frequency has been obtained. In the process of solving the optimization problem using classical single-variable optimization methods, an expression for the optimal slip frequency was derived, as well as the relationships between current magnitudes and the parameters of the induction motor stator and rotor winding phases. These were obtained based on the conventional mathematical description of a generalized AC electrical machine for its steady-state operation. The effectiveness of the proposed methodology has been proven using the example of an AIR225M2 induction motor with a power rating of 55 kW, for which the electrical loss dependence in a quasi-steady-state mode under a static load of Mc = 0.5Mnom was obtained. It was established that the optimal slip value for this induction motor is s = 0.038.
Originality. For induction motors of various power ratings, a universal objective function has been derived to minimize electrical losses as a function of slip frequency. This function enables the determination of a performance characteristic representing the dependence of the maximum attainable efficiency on the load torque on the shaft for induction motors of any power range.
Practical value. The research findings can be implemented in induction motor drive systems equipped with rotor speed sensors to enable automated self-regulation of the motor speed. This ensures the rotor operates at the optimal slip value across the entire load range of the driven mechanism.
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