Magnet wires find many applications in modern world. Magnet wires used for the electrical insulation in fly-back transformers, solenoids, sensors, adjustable speed drives etc. are subjected to multistress aging factors such as electrical (high voltage, high frequency), thermal and other environmental stresses. Due to the action of these aging factors degradation and aging of the insulation will occur and thereby lead to reduced life-time or premature failure. In order to identify the most important factors affecting the life-time of the electrical insulation, the insulation must be evaluated under simulated service conditions. This study is done by performing accelerated aging tests at high electrical stresses, elevated temperatures, and often at combined electrical and thermal stresses, and at high frequencies. The electrical phenomena behind the breakdown of the insulation have been studied. In this study accelerated life tests are performed on AWG 40 magnet wire. Life-time characteristics, probability of failures, and life-time percentiles are determined.

Electrical and electronic device insulation systems experience multiple stresses while in service. Insulation design engineers usually make attempts to study the behavior of insulation under multiple stresses to keep the size and weight of the electrical insulation at a minimum. In this thesis, magnet wire insulation properties under multiple stresses are studied. Magnet wires are used for insulation in transformers, flyback transformers, solenoids, sensors, motors, adjustable speed drives etc. The magnet wire insulation under study in this work is micrometers thick, yet they are expected to provide high breakdown strength, good windability, and resistance to moisture. Accelerated life tests are performed on two different AWG 43 magnet wires. Combined Weibull Electrical-Thermal life models and Electrical-Thermal-Frequency life models were successfully verified in this work. The statistical information like lifetime characteristics, probability of failures, and lifetime percentiles determined for the two different magnet wire insulation is helpful for a better understanding of their insulation properties.

Partial discharge testing is a nondestructive method of identifying possible premature insulation breakdown. Magnet wires are used in various electrical equipment like injection coils, solenoids, small transformers and motors. Winding wires used in high voltage systems are subjected to several stresses during operation, which considerably lowers their lifetime. A prolonged combined effect of these stresses causes aging of the wires, inception of partial discharge activity, and degradation of the organic material in the enamel coating and varnish used by the manufacturer. The tests were conducted for AWG 30 and AWG 31 twisted magnet wire samples. The samples are aged under accelerated conditions of high frequency, temperature, and pulsed voltages. As well as conventional sinusoidal voltages. This thesis is focused on the results of voltage, frequency, and temperature stresses on the magnet wires. The partial discharge inception voltage (PDIV) and breakdown voltages are measured for different twisted wire samples. A software tool is utilized to study these partial discharge patterns. Evaluation of the parameters charge intensity, pulse count, and pulse phase position are presented in 2- and 3-dimensional plots.