Newly developed insulation system for large type dc motors

Electrical insulating property in rotors and stators of rotating machines is one of important factors in life of the machines. For DC motors, mostly used from several ten years ago was natural resin insulation. The natural resin insulation, however, has no high reliance owing to the fact that its binding force gets weakened during high temperature and the insulation layers get relocated or stagger little by little during long use. The maximum tolerable temperature of the natural resin insulation is classified to be ?A? class, due to the above reason.