The stator insulation system for our synchronous machines is
Thermalastic Epoxy Insulation. This is a premium insulation system,
developed by Westinghouse and proven in more than thirty years
of outstanding performance on thousands of Westinghouse motors
and generators. Thermalastic is under continuous development to
maintain its position, as the world’s finest. The outstanding
record of Thermalastic can be attributed to the fact that it is
a mica-based insulation system. Mica has long been recognized
as the most reliable insulating material due to its superior dielectric
and voltage endurance capabilities.
Careful manufacturing procedures, including rigorous testing
at critical points in the process, assure a distinctly superior
insulation system. First, mica insulation is applied to the formwound
stator coils. The coils are then installed in the slots and the
completely wound stator is post-impregnated with epoxy resin in
a vacuum pressure tank. Next, it is transferred to a baking oven
for resin polymerization. The cycle is repeated for double protection.
The result is a stator insulation system free of corona-generating
voids, able to withstand prolonged voltage stresses, moisture,
abrasion, dirt, thermal cycling, and frequent starting surges.
Various types of Thermalastic insulation are used depending on
the physical size and voltage rating of the machines. On machines
over 7000 volts, slot sections of the insulated coil are wrapped
with a semi-conducting tape which, in conjunction with a corona-suppressing
semi-conducting coating applied at the ends of the straight portion,
protects the stator from corona damage. For very large diameter
machines, Thermalastic insulation is applied to individual coils.
Each coil is vacuum-pressure impregnated with solventless resin
and cured before being wound into stator core slots. An additional
resilient elastometric outer coating is available for applications
in which the insulation is subjected to abrasive atmospheres.
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