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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
Issued by: MOLM
Sheet No
3AAM101046 E
Rev. B
01.2023
Page 2 of 4
We r
es
erv
e
a
ll r
ight
s i
n t
his
doc
umen
t a
n
d i
n t
he
inf
or
mat
ion
cont
ain
ed
ther
ei
n. R
epr
o
duc
tion
,
us
e
of
dis
clo
su
re
to
th
ird
part
ies
w
itho
ut
ex
pr
es
s auth
ority
is
s
tr
ic
tly
f
or
bi
dden.
localised overtemperatures. This condition leaves
characteristic marks all over the machine.
The rotor core laminations become blue if the
temperature has reached 350°C (this can also be the
effect
of
very
heavy
startings).
Localised
overtemperatures in the stator can produce thermal
expansion very dangerous for the winding coils
whose insulation can crack.
The effect of prolonged period overtemperatures,
caused by continuous overloading or incorrect
dissipation of the heat, is the premature ageing of the
insulation.
The insulation materials become brittle and change
colour to darker appearance; moreover, fractures and
splits of insulating layers can be produced.
Conclusion from the visual inspection.
According to the observed situation of the winding, the
following conclusions can be drawn, and the consequent
actions are suggested to be taken
Observation
Action
Degree of contamination:
Presence of dirt, cooling ducts about to be
plugged.
Conductive dirt, low insulation resistance
Humidity, low insulation resistance
Cleaning and drying, if necessary
Cleaning and drying, if necessary
Drying
Finishing varnish
Mat, worn, cracked
Coming off
Winding and supporting elements
Loose slot wedges
Slot wedges coming off
Vibration marks
Bent coils
Insulation ageing
Darkening, slight embrittlement
Embrittlement, loose insulation layer
Cleaning and re-varnishing
Remove old varnish and re-varnish
Tightening *)
No action if less than 10%. Replacement if
more *)
Tightening, strengthen and re-varnish *)
Strengthen or re-do the winding *)
Cleaning and re-varnishing
Re-do the winding
*) A statement of an expert is absolutely needed
Cleaning and drying the windings.
The cleaning, drying and refurbishment of the
windings is matter of specialist and must be
carried out by trained and experienced people,
preferably under the supervision of a qualified
Service organisation.
Cleaning methods.
Blowing and vacuuming
Blowing and vacuuming are used if the dirt is dry and
can be removed easily. Vacuuming is the preferred
method, since blowing tends to redistribute the dirt or
move it deeper between the insulation layers.