On-line cure monitoring of next generation motor and transformer impregnates

A technique is described utilizing a sensitive dc megohmmeter to measure the on-line Insulation Resistance (IR) across sections of wire windings where a resin had been applied. The IR of well-cured sections usually is very high and allows for setting a minimum insulation resistance. When the insulation resistance is found to be below the minimum IR, the device is usually placed back into an oven for a longer cure. When the IR rises above the minimum, then the resin is said to be cured. Leakage current measurements during fabrication have been shown in this work to provide a strong indication as to the degree of cure of a resin or impregnate in a component. It will be discussed in this preliminary work how these leakage currents were measured throughout the manufacturing process for motor stators and lighting ballasts to determine how well these components have cured. This work was undertaken to provide a better understanding of the processing time necessary to achieve a well-cured component