Insulation life tests of multiple insulated wire cables in presence of high frequency and high temperature

The behaviour of insulated copper wire windings in the presence of power ac voltage and relatively high temperatures from the point of view of the insulation life is reasonably well known. However, the introduction of both modern multiple insulated wire cables and high frequency PWM-like supply voltages can give rise to a lower insulation life than in the previous case. A research program has been rigged to investigate two aspects of this problem. The first aspect regarded a comparison between the life curves behaviour of the same twisted pair enamelled wire specimens in ac high frequency voltage conditions and the life curves in PWM-like voltage conditions: the results showed that the above agings are not described by the same mathematical model. The second aspect regarded the study of a testing procedure to qualitatively estimate, in a relatively short time, the weight of the enamelled wire insulation endurance on the long term behaviour of a full insulation winding (represented by segments of an actual winding). The reported results of specific tests showed a way to achieve such a goal, therefore to save testing costs and time during the development of insulation of this type.