Improvement of Rotating Machinery Insulation Characteristics by Using Mica Paper Containing Aramid Fibrid

The authors developed mica paper containing a small amount of aramid pulpous particles (fibrids), which were obtained by adding a precipitant into a polymer solution under a high shear condition. This mica paper is characterized by high dielectric strength, high tensile strength and high cut-through resistance. This mica paper is especially suitable for dry tape in conductor and coil insulation, because of the good workability and good resin impregnability, even in the case of small binder content. A significant improvement of insulation characteristics in thermal stability and mechanical fatigue resistance was attained by an application of this mica paper to rotating machinery coil insulation.