Search

This letter describes a high-resolution technique called thermally stimulated depolarization current (TSDC) that can be used for the measurement of space charge accumulation in the medium voltage magnet wires operating on pulsewidth modulated (PWM) inverters. Index Terms--Fast rise time pulses, induction motors, inverterfed drive motors, magnet wires, space charge injection.

In this paper, the effectiveness of stress grading coatings (SGCs) on form wound stator coil groundwall insulation under fast rise time pulses is analyzed. The combined performance of the stress grading coating and the semiconductive slot coating is studied under fast rise time transient voltages. During the rapid rise of voltage, the high stress moves from the stress grading coating to the semiconductive coating at the end of the slot. According to the results, it is evident that the design of both the stress grading and semiconductive slot coatings must be done together for effective stress relief. The use of materials with varistor behavior in the stress grading coating, combined with a high conductivity semi-conductive slot coating, is analyzed as a solution to the high stress that develops at the slot end of form wound stator coil groundwall insulation of inverter fed drive (IFD) motors. [ABSTRACT FROM AUTHOR]