Electrical aging tests on enameled wire exposed to gamma irradiation

Stator windings of low voltage electrical motors are usually insulated by means of organic enamels. If motors are used in particular industrial plants or in nuclear applications, the enamel adopted to insulate the motor stator windings may be exposed to very intense gamma photonic irradiation fields. In this research activity, attention has been focused on the potential influence of gamma irradiation dose on the performances of an electrical insulation system based on enameled wires having a thermosetting matrix. The aim of this research activity is to assess the prospects of exploitation of such insulating materials inside electromechanical devices intended to operate in presence of gamma photonic fields as in the frame of nuclear plant dismantling or, in general, of the manipulation of radioactive products. Suitable specimens, insulated by the considered enamel, have been set-up using enameled wire exposed to gamma photonic irradiation within a panoramic irradiator endowed with Co⁶⁰ gamma sources. These pre-aged specimens have been subjected to electrical aging tests up to the enamel breakdown condition, chosen as end-point criterion, in order to study the electrical performances of the considered wires. The peak to peak voltage amplitude of the considered waveform has been set higher than the partial discharges inception voltage level in order to work in presence of surface partial discharges activity. Enamel life curve has been plotted in order to point out gamma irradiation dose influence on the performances of the considered insulating material. The obtained results show the significant effects of the exposure to a gamma irradiation field on the performances of the considered insulating enameled wire.