Electrical insulation of an AC propulsion motor for the DEEPSTAR 20,000

The DEEPSTAR 20,000 vehicle will be propelled by an a-c induction motor designed for light weight, reliable operation at depths to 20,000 feet. It is a 2-pole a-c squirrel-cage induction motor which operates at a speed of 3450 rpm at full load, developing 10 horsepower at 60 hertz at 20,000 feet. The voltage established for 60 Hz operation is 82 V ac line-to-line. It is delta connected internally for a high order of system efficiency and compatibility with the controller. The motor operates in a petroleum based fluid maintained at a slight positive internal pressure relative to ambient. The motor windings are polyimide-enameled copper wire impregnated with diphenyl oxide resin varnish. Slot and ground insulation is polyimide film bonded on both sides of polyamide fiber paper, totaling about 10 mils in thickness. The insulation system offers reliable electrical operation with effective cooling characteristics when operated under load. Testing has been performed on this design in air, oil, and seawater-contaminated oil. The conditions of the peformance tests included sea level, hydraulic pressures up to 13,500 psi, and repeated cycling between the extremes.