The vibration of windings and the core determines the tank vibration and the overall noise level of transformers.Previous studies ignored the coupling vibration between the core and winding resulted from structural connection

and the vibration of the core and windings are assumed as independent vibrating sources and do not affect each other.However

such an assumption is too ideal to reflect the actual vibration inside transformers.In order to get a comprehensive understanding of the coupling vibration between the core and winding in oil-immersed transformers

this paper establishes a measurement system based on fiber optic accelerometers.Experiments are conducted on a three-phase 50 kVA transformer under the on-load

load

and the variable-load test

respectively.The results show that

in no-load test

the core vibration transmits to winding and drive windings to vibrate at the same vibrating frequencies as that of the core

but the amplitudes are higher than that of the core vibration.The acceleration of winding driven by Lorentz forces is higher than that of the clamping frame

which demonstrates winding vibration can hardly transmit to the core and result in the core vibration.The harmonics of internal vibration depends on the magnetic flux density inside the core and the acceleration of core decreases with the decrease of the amplitudes of excitation harmonics.