ABB AMD Rg 355 Installation, Operation And Maintenance Instructions page 92

Installation, operation and maintenance instructions

High voltage flameproof motors for explosive atmosphere
AMD Rg 355-400-450-500
Medium voltage windings maintenance
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
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
Degree of contamination:

Presence of dirt, cooling ducts about to be
plugged.

Conductive dirt, low insulation resistance

Humidity, low insulation resistance
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 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.
very heavy startings). Localised
Observation
Sheet No
3AAM101046 E
Rev. B
Page 2 of 4
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
Action

Cleaning and drying, if necessary

Cleaning and drying, if necessary

Drying

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 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.
01.2023
Issued by: MOLM