Efficiency and Harmonic Assessment of a PWM-Inverter-Fed Three-Phase Induction Motor Under Variable Mechanical Loading: A Data-Driven Steady-State Study

• Muhammad Romadhoni Indra Firmansyah

  Universitas Tulungagung

  Penulis

Three-phase induction motors remain dominant in industrial drives because of their robustness, low maintenance cost, and compatibility with power-electronic control. However, their efficiency is strongly load-dependent, particularly when oversized motors operate below 50% of rated load. This paper revises and extends a classroom-level analysis into a structured, data-driven study of a 1.5-kW three-phase induction motor supplied by a two-level PWM inverter. Four mechanical-load scenarios, namely 25%, 50%, 75%, and 100% of rated load, are evaluated using a steady-state efficiency, loss, slip, and current-harmonic model. The reconstructed dataset shows that PWM operation improves efficiency relative to the direct-on-line reference at all load points. At 25% load, efficiency increases from 58.59% to 61.98%, while the highest efficiency of 84.59% occurs at 75% load. The full-load condition yields slightly lower efficiency, equal to 84.03%, because current-dependent loss increases. The current THDi decreases from 18.2% at 25% load to 8.6% at full load, but the 5th and 7th harmonic components remain dominant across all operating points. The results demonstrate that PWM control is useful for partial-load operation, but its benefit must be interpreted together with harmonic distortion, thermal loading, and performance-to-loss ratio rather than efficiency alone.

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