Electrical insulating material and stator bar formed therewith

A stator bar comprising:

• a plurality of conductors arranged in a group;
• insulation insulating the conductors from each other;
• groundwall insulation surrounding the group of conductors, the groundwall insulation comprising first and second insulating layers, the first and second insulating layers each comprising:
• a mica paper having first and second surfaces on opposite sides of the mica paper;
• a woven fabric on the first surface of the mica paper;
• and
• a resin binder permeating the woven fabric and bonding the woven fabric to the mica paper;
• wherein the first insulating layer further comprises oxide particles dispersed in the woven fabric, and wherein the second insulating layer is free of oxide particles.

A stator bar comprising:

• a plurality of conductors arranged in tiers;
• insulation insulating the conductors from each other;
• groundwall insulation surrounding the tiers of conductors, the groundwall insulation comprising first and second insulating layers, the first and second insulating layers each comprising:
• layers of a mica paper;
• a woven fabric on at least one surface of the mica paper;
• and
• a resin binder permeating the woven fabric and bonding the woven fabric to the mica paper;
• wherein the first insulating layer further comprises oxide particles dispersed in the woven fabric, the oxide particles being at least one oxide chosen from the group consisting of silicon dioxide, aluminum oxide, titanium dioxide and zirconium oxide, the oxide particles having a particle size of about 0.005 to about 0.05 micrometers;
• wherein the second insulating layer is free of oxide particles;
• and
• wherein the first insulating layer constitutes about 10 to about 90 percent of the groundwall insulation.