ВПЛИВ НЕСИНУСОЇДАЛЬНОСТІ НАПРУГИ ЖИВЛЕННЯНА ТЕПЛОВІ ВТРАТИ В АСИНХРОННИХ ЕЛЕКТРОДВИГУНАХ

The work investigates the influence of non-sinusoidal supply voltage on the magnitude and structure of thermal losses in induction motors. The relevance of the topic is determined by the spread of nonlinear loads and converter technology in local power supply networks of industrial and municipal facilities, where non-sinusoidal voltage causes current harmonics, additional heating of the windings, and accelerated aging of the insulation of induction motors. The aim of the work was to quantitatively assess the change in total thermal losses of an induction motor as a function of the voltage harmonic distortion level and to develop engineering-based guidelines for reducing the permissible load. Research methodology. The study used regulatory approaches to power quality assessment, data from peer- reviewed scientific publications, and a calculation model of a three-phase squirrel-cage motor with a rated power of 11 kW. The analysis employed harmonic representations of voltage and current, relations for determining copper, iron, mechanical and additional load losses, and an engineering assessment of temperature rise based on the relative change in total losses. Results. It was established that in the studied induction motor, as the voltage total harmonic distortion in the supply network increases to 5 %, 8 %, 12 % and 15 %, the total thermal losses increase by 79.6 W, 127.6 W, 191.6 W and 239.9 W, respectively, compared with sinusoidal supply. The additional load losses and iron losses were shown to increase most intensively. The stator and rotor copper losses also increase due to the higher RMS current and the appearance of negative-sequence components. At voltage total harmonic distortion above 8 % without adjustment of the operating mode, a noticeable decrease in efficiency is observed, which creates a practical need for motor derating. The scientific novelty of the study lies in proposing a simplified engineering model that links levels of harmonic voltage distortion to the redistribution of components of induction motor losses and to the threshold for reducing the permissible load. The practical value of the work lies in developing a thermal risk assessment scheme and selecting harmonic compensation measures suitable for operational practice.