Advances in direct current high voltage continuity testing. Report of the NEMA magnet wire MW-7 technical committee

The NEMA magnet wire technical committee has been investigating direct current high voltage continuity (HVC) testing of magnet wire for several years. This paper describes efforts to better define (1) a continuity fault, (2) the continuity testing equipment, and (3) a new HVC electrode option. The description of the DC-HVC testing equipment in NEMA MW-1000 Part 3 needs to be improved to reduce the variations allowed in the equipment design and the corresponding wire testing results. The description of the equipment can be improved even without a better definition and understanding of an HVC fault. Investigations of the fault current waveform at the fault circuit has resulted in new insights in the detection and definition of HVC faults. The other major HVC issue still. Remaining is eliminating the double counting of faults by the dual sheave electrodes. A new graphite fiber electrode may resolve the issues of double counting without the potential of introducing any additional problems.