Question { NTPC, 20286 }

Why a Transformer Noise during its running condition ??

Answer

transformer noise may be due to,
# Improper core insulation
# aging through continuous running condition which leads to
expansion of core material(Magnetostriction)

Generally if T/F is found noisy at full load conditions and
I think that cannot be avoided but minimized by applying
relevant lubricant over the core.

Question { 10294 }

-What is leakage current . how much leakage current is
allowed.

Answer

Leakage current is wastage current which occurs due to
improper insulation within the unit, and is also dangerous
by direct human contact. Leakage may be between,
Input to ground,
Output to ground, or even
Input to output terminals.

According to IEC standards, 10mA flow is accepted when 2kV
is applied across the above mentioned terminals when they
are electrically isolated.