Abstract: Fluid-cooled electrical apparatus characterized by a new and improved pump for circulating the fluid within the apparatus. The pump has a motor portion in fluid communication with a pump portion, non-electrically conductive bearings supporting a common shaft between the two portions. The bearings being comprised of a polyamideimide thermoplastic resin.

Abstract: A transformer motor pump unit for circulating a fluid in a transformer characterized by a rotating pump shaft mounted in non-electrically conductive bearings, means for detecting shaft displacement due to bearing wear, and a static arrester grounding the pump shaft and all rotating parts for preventing static electricity buildup on the shaft and subsequent discharge from the shaft to the bearing area. Power circuit means for operating the pump includes the static arrester as a control circuit for tripping the pump out of operation should mechanical failure occur.

Abstract: Fluid-cooled electrical apparatus having a new and improved pump for circulating the fluid within the apparatus. The pump has a motor portion in fluid communication with a pump portion, non-electrically conductive bearings supporting a common shaft between the two portions, and means for detecting shaft displacement due to bearing wear. Electrically conductive contact rings disposed within recesses in the bearings' sleeve and thrust surfaces complete an electric connection with the shaft in the event of bearing wear. Circuit means connected to the electrically conductive contact rings deenergizes the motor when the contact rings detect predetermined bearing wear.