Adhesion properties of different rotor pole wires

A study was conducted to compare the effect on the turn-to-turn adhesion of double daglass plus heavy enamel square wire to that of single daglass plus heavy enamel square wire. Comparisons were made with two adhesives — a high strength Class H epoxy and a medium-strength Class F polyester. Test samples were made for shear, flexural and tensile strength. Only the shear data had any significance. A typical shear sample was a 2 wire by 3 wire rectangle 3 inches long of #5 square wire. The compressive force measured was that to push the center 2 wires out of the array at an elevated temperature of 180°C. A Lucas Tester at .200 in./min. was used. The elevated temperature is a simulation of the actual maximum operational regime of a wire-wound field coil. The samples were aged for 2499 hours at 220°C which is approximately equivalent to 30,000 hours at 180°C and 170,000 hours at 155°C. It was found that with polyester the sdg-he insulation was considerably stronger than ddg-he material. With epoxy the wire insulations showed rough equality while continuously gaining in strength. sdg-he insulation was adopted as the standard pole wire.