Dielectric parameters study of insulation wire free of volatile organic compound

Nowadays, polyimides, polestherimides and polyamide-imides are widely used in electrical machines winding insulation. However, the manufacturing process of these classical enameled wires is expensive and very polluting. The polymerization of the insulating layers (20 passes) is obtained by the combined action of heat at 700°C in big ovens (20 meters) and pollutant solvents included in the initial varnish. In this study, new enameled wires based on free-solvent manufacture are studied. This type of insulation is obtained in 2 passes. An UV-polymerized layer is firstly deposited on the conductor. Then, a second thermoplastic layer is extruded. The purpose of the work detailed here is to explore this new type of wires for possible application in the domain of electrical machines. Their physicochemical properties are analyzed by differential scanning calorimetry and thermo gravimetry. Partial discharge and breakdown tests are performed at the initial state and during thermal ageing at 250°C. The results are cross-correlated in order to differentiate and understand the dielectric behavior of the new wires.