Mechanical Power of Induction Motors with Non-sinusoidal Power Supply

When induction motors are powered by solid-state voltage and frequency converters, the torque on the shaft is created by the first harmonic of the current, and the higher harmonics of the cur-rent only create losses in the stator winding. The purpose of the work is to develop a methodolo-gy for determining the permissible mechanical load of asynchronous motors at non-sinusoidal currents. To achieve this goal, it is necessary to determine the influence on the mechanical pow-er of the motor of higher current harmonics, the effective values of which depend on the control parameters of semiconductor voltage and frequency converters. For quantitative assessment of their influence on mechanical power, it is proposed using the current harmonic coefficient as a generalized parameter as the ratio of the sum of the effective values of higher current harmonics to the effective value of the first harmonic. As a result of researches, the expression for calcula-tion of the coefficient of admissible mechanical load of the motor concerning a nominal value taking into account the coefficient of current harmonics is received. Scientific novelty: for the first time, the analytical expression for determining the coefficient of permissible mechanical load of induction motors powered by semiconductor converters of voltage and frequency using the current harmonic coefficient is obtained. Practical significance: the proposed methodology allows checking the selected induction motor for heating when supplied from semiconductor converters of voltage and frequency for a given mechanical power of the working mechanism.