Magneto-Mechanical Resonance in a Model 3-Phase 3-Limb Transformer Core Under Sinusoidal and PWM Voltage Excitation

This investigation presents the measurement results of acoustic noise and vibration of a model three-phase three-limb transformer core under sinusoidal and PWM voltage excitation for assigned value of modulation index with switching frequency from 1 kHz to 3 kHz at no-load condition. Results show that the acoustic noise decreased around 2 (dBA) with increasing switching frequency. However, magneto-mechanical resonance phenomenon was observed at 3 kHz vibration frequency, which could cause excess acoustic noise under some excited conditions.