A new reliability diagnostic for aged insulation systems based on cure monitoring of "motorettes" of catalyzed mica tapes wrapped on aluminum bars

A new method to verify and validate the cure of an impregnate used to bond the magnet wire of a random wound stator or transformer was first introduced in 1998. This technique showed promise in saving manufacturing time by accurately determining the cure-ensuring that large production runs could be run more efficiently thus saving time and energy. This technique has now been used to determine the reaction times of catalyzed tapes used on form-wound bars in the VPI process. This technique was used to determine differences in chemical reaction curing rates between different tapes with varying concentrations of catalyst. These tapes can be used together in the same insulation system. This approach may possibly serve to monitor the aging effects on coils over time by subsequently heating to cure process temperature to determine any changes in the leakage current from the original data. This technique calls for more study as to its potential to better understand the long-term cycle-life of electric motors, transformers, and other power carrying devices. The use today of this new technique on form wound bars and its possible use to better understand the long-term aging issues will be discussed in this paper.