CONSEQUENCES OF NEW VOLTAGE SHAPES GENERA TED BY INVERTER ON ROTATINGMACHINE INSULATION MATERIALS

Use of inverter drive for rotating machines speed control leads to the application of new stress on stator insulation materials. Tile integr ity of these materials under such stresses has therefore to be studied . Thanks to specially equipped motor, the different voltage shapes hav e been identified. Very short rise time fronts, large overvoltages and high oscillation frequencies are obtained. These voltages are then re produced on laboratory samples (Polyethylene Terephtalate). The main r esult is the existence of trapped surface charges related both to the rise front value and to the existence of polar mechanisms in the mater ial bulk. The consequences of this surface charge existence on the rel iability of a real system are then discussed.