7 electric motor insulation classes

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7 electric motor insulation classes

Excessive motor temperature, or Over Temperature can result from motor size and type selection or incorrect installation,   as well as an operating environment that is hotter than the design conditions. Many motor problems, including overheating, can be avoided by understanding how the motor works and the conditions in which it will be used.

Today we introduce motor thermal insulation classes, formally called Insulation Class or, for easier communication, shortened to Class alone.  
which Class of the insulation indicates the materials, properties and performance of that motor's insulation system. Let us look at the classes.

Electric motor insulation classes ( Insulation Class )

Insulation class	Temperature tolerance	Details
Y	90 C	Insulation with a maximum temperature tolerance of 90 degrees Celsius.
A	105 C	Cotton tape, silk, fibre or paper insulation impregnated with varnish or immersed in oil, such as varnished cloth and Bakelite. Its maximum temperature tolerance is 105 degrees Celsius.
E	120 C	Polyester, urethane, epoxy, melamine and phenolic resin insulation, with a temperature tolerance of 120 degrees Celsius.
B	130 C	Mica, glass fibre and asbestos insulation combined with binders such as epoxy. These materials can withstand 130 degrees Celsius.
F	155 C	Mica, glass fibre and asbestos insulation combined with binders such as silicone, varnished glass fibre, asbestos varnish and polyamide. Its temperature tolerance is 155 degrees Celsius.
H	180 C	Silicone elastomer, mica and glass fibre insulation combined with binders such as silicone resin and Polytetrafluorethylene(PTEE) with a temperature tolerance of 180 degrees Celsius.
C	>180 C	Mica insulation or Poreeclain or Glass or quartz crystals. These are commonly used for insulators because of their greater mechanical strength compared with other insulation types.

Varnish impregnation helps coating reach every part of the winding, improves strength against vibration and reduces the chance of dust settling between windings. Most insulation materials commonly used today can withstand the temperatures specified by insulation class Class F with a maximum temperature tolerance of 155oC Some motor models may instead use insulation class Class H with a maximum temperature tolerance of 180C