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What is the main cause of noise in the transformer?
Magnetostatiction
Mechanical vibration of tan
mechanical vibration due to lamination
All of these
All of these
Transformer noise, primarily a hum at twice the line frequency (100 Hz for a 50 Hz system), results from the physical deformation of the core and structural components. Magnetostriction, mechanical resonances in the tank, and the vibration of loose laminations collectively contribute to the audible sound emitted during operation.
Transformer noise, primarily a hum at twice the line frequency (100 Hz for a 50 Hz system), results from the physical deformation of the core and structural components. Magnetostriction, mechanical resonances in the tank, and the vibration of loose laminations collectively contribute to the audible sound emitted during operation.
fnoiseтАЛ=2├ЧfsupplyтАЛ тАФ The fundamental frequency of transformer humming noise is twice the supply frequency.
╬ФLтИЭB2 тАФ The change in length due to magnetostriction is proportional to the square of the magnetic flux density B.
The primary mechanism is magnetostriction, where ferromagnetic materials change their physical dimensions when subjected to a time-varying magnetic field. As the flux density varies at double the frequency, the core core pulses, inducing mechanical vibrations in the tank walls and internal lamination stacks. These vibrations, if not properly dampened or tightened, propagate through the transformer structure as audible noise.
Magnetostriction is the property of ferromagnetic materials to change shape during magnetization.
Loose core laminations increase noise due to physical impact and vibration.
Transformer tank panels act as diaphragms, amplifying low-frequency magnetic vibrations into audible sound.
Increasing flux density (over-excitation) significantly increases the noise level.
Magnetostriction is an intrinsic property of the silicon steel used in cores.
Mechanical vibrations are often mitigated using anti-vibration pads or tighter clamping bolts.
Option B (mechanical vibration of tank) refers to the amplification of core noise by the enclosure.
D is correct тАФ All listed phenomena (magnetostriction, tank vibration, and lamination movement) contribute to the cumulative noise emitted by an operating transformer.
For exam purposes, remember that transformer noise is dominated by the second harmonic of the supply frequency because the magnetic cycle completes two saturations per single cycle of current.