Motor Insulation Systems (3)

3. Design Variations

The types and amounts of insulating materials used can vary considerably from one (1) manufacturer to another. Some manufacturers may omit some or all of the paper insulating components and depend upon the varnish coated wire to serve in their places. This is, however, more typical of fractional horsepower (HP) motors, due to the cost of the added insulation in relation to the overall cost of the motor. Manufacturers often offer various motor product lines that provide a variety of application benefits at various price levels. One such example is the “inverter duty rated motor”. Some of these product lines include differences in the designs of their insulation systems. From time to time, new insulating materials are introduced with improved electrical, mechanical, thermal or chemical properties. An example of new magnet wire insulation technology is Phelps-Dodge’s Inverter Spike Resistant (ISR)® wire. This wire was originally purported to provide adequate protection against voltage overshoot caused by the fast rise times of IGBTs without the need for additional motor phase papers or sheets.
Field reports, however, have shown that this wire alone provides only a minimal extension to motor longevity.


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