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Installation, operation and maintenance instructions
High voltage flameproof motors for explosive atmosphere
AMD Rg 355-400-450-500
Medium voltage windings maintenance
insulation resistance increases until it reaches a
stable value.
Varnishing of the windings.
The windings' surfaces are normally coated with a
protective layer that seals the windings, improve
somewhat the tracking resistance
cleaning easier. This is obtained by spraying or
brushing a finishing varnish
exposed area of the winding.
The finishing varnish may, after long operating
time crack or peel off to certain extent. This can be
corrected by giving on the damaged surfaces a
new coat of varnish. This is recommended when:
The old finishing varnish flakes, cracks or
peels off.
The surface of the winding is too rough (the
dirt can stick to it)
The materials on the surface of the insulation
or the tyings on the overhangs have moved.
The windings should be cleaned with utmost care
before a new coat of varnish is given, in order to
be sure that no dirt will be left under the new coat
of varnish.
The varnish is usually applied with a spray (one or
two coat). Do not apply the varnish if the winding
is warm; the surface temperature should be less
than 40°C (104°F). One should try to apply the
varnish between the coils and in general between
the parts that are not easily reached. Thick coat of
varnish should be avoided as they dry slowly.
Rotating parts should be left to dry at least 24
hours at ambient temperature
them into use.
Voltage test.
A voltage test is used to check for electrically
weak spots
insulation failure during servicing. It is the only test
that can give information about the soundness of
the insulation barrier; anyway the decision about
the application of high voltage to an old winding is
matter of specialist. This test is carried out during
repair or, depending on the situation, during
overhauls. DC or AC voltage can be used; DC is
seldom used for the sizes of machines as treated
in this manual and involves the application of a
voltage that is 1,6 times the root-mean-square
value of the AC test voltage.
and makes
or resin on the
before bringing
in the windings that may lead to
Sheet No
3AAM101046 E
Rev. B
Page 4 of 4
The suggested values for voltage tests, carried out
with AC are:
for service and repair
for periodical test during overhaul
where U is the rated voltage of the motor.
Work
safety
principles
maintenance.
Winding maintenance involves:
Handling hazardous solvents, varnishes and
resins.
Dealing
with
flammable
varnishes.
Testing at high voltage.
Some general safety measures are remembered
as follows:
Avoid
breathing
dangerous
fumes; ensure proper air circulation at the
work site and use respiration masks.
Wear gloves and suitable clothing to protect
the skin. Use always protective cream
The frame of the machine, the windings
terminals and the spray-varnish equipments
should always be earthed during spray-
varnishing.
Do not smoke, eat or drink at the work site.
Take the necessary precaution when working
in cramped spaces.
Only people trained to do high voltage works
can carry out a voltage test.
In any case refer to all the instruction available on
the working area and to the national rules of the
Country where the job is in progress. Look also to
the handling instructions that are printed on the
warning labels of the dangerous substances
packing.
Issued by: MOLM
01.2023
1,5 x U
1,25 x U
during
winding
solvents
and
substances
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