Electric motors have insulation systems that protect them from shorts and contaminants. There are different classes of insulation that are effective for increasing rated temperatures. As defined in Image 1, there are four common classes of insulation, which correspond to their temperature class and define the maximum temperature the insulation system is rated. Beyond this temperature, the insulation will degrade, and premature failure of the insulation system and motor will occur.
The insulation system of the motor protects the windings from environmental contaminants and provides an insulating layer between wires in the winding, as well as protection from the windings shorting to ground or other wires within the stator coil. There are many aspects of the insulation system design, but focusing on the stator windings shown in Image 2, there are multiple levels of insulation. The wire itself is insulated, and there are sheets of flame-resistant material inserted into the slots, between phases and within other parts of the winding to protect the windings during assembly and while in use. The insulation material used may vary depending on the specific application requirements. Finally, the stator is coated with an insulating varnish that fully penetrates the winding and slots. There are different methods of applying the insulating varnish, and several treatments may be applied if the stator will be installed in a harsh environment.
If the insulation system were to fail, the motor frame could become energized, which could result in injury or death. For this reason, motor frames must be properly grounded to limit this potential.
For more information about pump drivers, check out Drivers Application Guidebook: Electric Motors.
