Fastwatt LLC, in collaboration with GE Research, proposes to develop a novel non-destructive insulation tester that is compact, portable and provides multiple functions. It can be used as a part of design validation or qualification tests for components such as laminated busbars, cables and transformer/ machine windings. The tester consists of a voltage source pulser which can output medium voltage DC, AC or PWM, including multi-level waveshapes. The tester will be built with a scalable stack of high-frequency MOSFET power bridges. For typical test loads such as laminated busbars, transformer insulation, and machine winding samples, the load capacitance and hence the tester power requirements will be sufficiently small to allow operation from a 120 V, 15 A input. The tester will be designed to act as a power amplifier that follows an input signal from a benchtop function generator - this will allow insulation testing at a variety of DC, AC or mixed waveforms. Partial discharge sensing and measurement of capacitance and dissipation changes will be incorporated to detect insulation defects or onset of failure. Fast protection will be incorporagted in the tester to prevent damage in case of failure of the insulation test samples. During the Phase 1 Base program, we have worked on improving the packaging of the tester, incoroporated protection for output short circuits and improved the startup sequence of the tester.
Benefit: The proposed tester will be useful for many applications such as testing of laminated busbars, machine winding samples, cables, transformers, bushings, and switchgear. Presently available testers are limited in their capability to validate insulation under mixed DC and switching frequency voltage stresses such as those typical in motor drive laminated busbars. The proposed tester can provide this unique functionality for many industrial and military customers. An early prototype at low voltage (+/-1200 V) has been used for testing a cable connecting a PWM drive to a motor in an electric aviation application. The tester proved to be highly useful since it revealed an issue with the cable termination/ connections during accelerated life-testing, even though the supplier was confident of their initial design. The system integrator and cable supplier were able to rectify the issue through design iterations and hardware validation through accelerated life-testing with the tester The proposed effort will sclae the concept to medium and high voltages and add functions such as PD sensing. Many equipment designers and test labs have expressed interest in having access to a medium voltage insulation tester with the proposed capabilities. During the Phase 1 Base project, we have worked on improving the TRL and packaging of the tester.
Keywords: Insulation, Non Destructive Testing., cables, Pulse tester, Partial Discharge Testing, PWM dv/dt stress, Bus Bars, shipboard power distribution
