Analysis of Speed Resonance Phenomena in Induction Motors under No-Load Conditions

This paper investigates the speed resonance phenomena observed in induction motors under no-load conditions, focusing on both analytical and experimental approaches. Although induction motors are generally assumed to operate stably at no load, oscillatory behavior in rotational speed may occur due to the interaction between electromagnetic torque characteristics and mechanical system dynamics. A mathematical model of the induction motor is formulated, incorporating slip-dependent torque characteristics, rotor inertia, and damping effects. The analysis reveals that speed resonance is strongly influenced by both the electrical and mechanical response characteristics. Parametric studies are conducted to clarify the conditions under which resonance occurs. To validate the analytical results, experiments are carried out using a test motor system under controlled no-load conditions. The measured speed fluctuations and frequency characteristics show good agreement with the predicted resonance behavior. The results confirm the validity of the proposed model and highlight key factors that govern the onset of instability. This study provides useful insights into the mechanism of speed resonance and contributes to the design and operation of stable induction motor systems.