A new bond strength test method for testing of bondable magnet wires

The present helical coil test method as specified in ASTM D-1676 and NEMA NW-1000 presents some difficulties when a wide range of wire sizes is being tested. Members of the NEMA Magnet Wire Technical Committee are currently engaged in the evaluation of new bond strength test methods which have been found to minimize these difficulties and provide more consistent results. The new method uses a tested figure-eight coil that is then bonded and tested with a stress/strain analyzer. The author explains the new test procedures and compares them to the existing ASTM and NEMA standards and a proposed IEC test for bondable winding wires. The results of the testing that has been performed to date on various sizes of bondable magnet wires are summarized. The method provides several advantages over the present helical coil method.<>