Electrical Transformer Noise Reduction and Operation | Every
transformer does make some noise, but it becomes conspicuous when the size is
large. The noise are hum is due to the fact that the core, which is made up of
thin laminations, vibrates because of the alternating magnetic flux, and
therefore expands or contracts ever so slightly with each cycle magnetization
this causes the audible hum. The contraction caused due to magnetization is
called Magnetostriction.
Electrical Transformer Noise Reduction and Operation
 |
| Electrical Transformer Noise Reduction |
The
transformer core must be tightly clamped together to reduce the hum. The flux
density should also be reduced as
much s possible, but there is a practical limit to this. Sometimes, under
unfavorable conditions of poor design or construction, the hum gets multiplied
100’s of times due to resonance. This should not be permitted.
The noise
and hum reduced by large transformers in urban areas often reached such high
values has to be a source of disturbance and annoyance to the people living
nearby. The noise level decreases quickly with distance. i.e. By some 6 dB for
every doubling of the distance, so that at about 200 feet the reduction could
be about 26dB. Transformer should therefore be located as far away from
residential areas as possible.
Where they
have to be located in heavily populated places, one method adopted to reduce
the noise is to install the transformer inside an enclosure which is made sound
proof. Brick walls lined with acoustics material are quite effective and all
connections should be by underground cables. When the size is large and the
voltage is high, the radiators could be mounted outside the enclosure and
connected to the transformer by flexible pipe connections. The transformer
itself is mounted on resilient pads.
Air inlet
and outlet ducts are lined with sound absorbing material to deaden the noise of
ventilating fans which should admit sufficient quantity of air to take away the
heat produced by the transformer. It is not possible to build conventional
enclosures around the large transformer, because of the high voltage bushings
and clearances required.
This
difficulties has been solved by M/S AEI for a 180 MVA outdoor transformer by
building an acoustic enclosure comprising a double wallet sheet shell, filled
with viscous compound, round the transformer tank leaving out the bushings and
the radiators. Sufficient space is left inside to permit normal maintenance.
The transformer is mounted on one 1 inch thick cross ribbed neoprene rubber
mats to limit the ground borne noise.
Final
Word
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