AN ENAMELED WIRE WITH A SEMI-CONDUCTIVE LAYER: A SOLUTION FOR A BETTER DISTIBUTION OF THE VOLTAGE STRESSES IN MOTOR WINDINGS
Résumé
Purpose-The paper analyzes a possible improvement of PWM fed motor insulation according to a principle developed by the high voltages industry. The proposed principle consists in using a specific enameled wire made with an additional semi-conductive layer on its outer surface. Design/methodology/approach-Experimental study is realized in order to measure partial discharge activity with three technologies: Classical enameled wire, enameled wire with an external conductive layer (silver paint) and enameled wire with an external semi-conductive layer (2% of carbon nanoparticles). Simulations are achieved in order to understand the behavior of the new semi-conductive wire. Findings-The contact resistance of the semi-conductive enameled wire must be lower than 50 MΩ in order to ensure lower electrical constraint and higher PDIV. Research limitation/implications-It is impossible to determine the contact resistance. In our model it is assumed equal or lower semi-conductive layer resistance. Practical implications-Random windings of motors used in low pressure environment. Originality/value-The presented approach is a step toward the design of electrical machine by moving PDs towards critical zones, near the coil connections. Additional small balls of varnish at this area, strongly increase the PDIV of the coil.
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