Charge decay on enamel wire surface

Partial discharge resistant enamel insulation filled with chromium oxide (Cr₂O₃) has been developed recently. In the paper, dynamics of surface charges on samples of the material is analyzed and is compared with that on conventional enamel. The experiments were conducted on test objects prepared as windings of enameled wires. Surface charging was implemented using dc corona from a needle electrode which was placed against the grounded winding. After charging, the potential induced by deposited charges was measured by non-contact technique. The surface charge density pattern was reconstructed utilizing Φ-matrix method. The decay of charges accumulated on insulation surfaces was recorded. It was found that the decay process was considerably faster for the filled enamel than for the conventional one, which may be one of the factors contributing to the improved partial discharge resistance of the former.