In the variable frequency speed regulation process, high frequency, high voltage resonant voltage pulse easy cause insulation materials of partial discharge, destroy the insulation material to shorten the service life of the frequency conversion motor(In the process of application of many AC frequency conversion motor operating life of only 1-2 years, some even insulation damage in the test run), For a prolonged period of variable frequency motor test researchers have put forward three kinds of solutions, First, shorten the length of cable between the the inverter and electrode to reduce charging voltage. Second, increase the electromagnetic wire insulation layer thickness, Add additional insulation in the ends of the coil and different phase interface. The third use of insulated magnet wire with Corona corrosion ability. Three methods all has direct or indirect relationship with insulation material, Therefore the corona resistant insulating materials has become a hot spot of research in the field of variable frequency motor insulation.