Experimental Comparative Investigation on Alternative and Commercially Available Wire Insulations Based on Partial Discharges Activity

To provide better control, energy efficiency, compactness and improvement of AC motors performance, the employment of power converters has increased during the last decades [1] , [2]. A faster rise time of the repetitive impulsive voltages results in a bigger voltage overshoot providing more chance to exceed the partial discharges (PD) inception field in turn-To-Turn insulation. Considering prolonged service, the PD activity might lead to premature failure and/or electrical insulation breakdown, since low-voltage electrical machines' winding is often made by Type I insulations (i.e., organic materials). Apart from the reliability-oriented design approach [3] , [4] , an alternative solution might be represented by the adoption of corona-resistant insulations (i.e., Type II insulation, mixed organic-inorganic insulating materials). For Type I, the impact of PD activity on life reduction is significantly higher where failure times of minutes in the presence of PD can be observed [5]. Type II, which is PD resistant by nature and is normally employed in high-voltage electrical machines, can be proposed as an alternative solution to reduce the influence of PD, and ensure extended lifetime in low-voltage electrical machines. Relying on this paradigm shift, two commercially available insulated wires were selected i.e., Glass fibre (as Type II) and PEEK (Polyether Ether Ketone, as Type I) insulated wires, for an experimental comparative study on PD activity. In fact, the paper compares and discusses the performance of the chosen wires when specimens are electrically stressed with repetitive unipolar positive and negative impulse voltage waveforms. In particular, the PD activity is evaluated through PDIV, PDEV and RPDIV at room temperature and atmospheric pressure for several rise time value of excitation voltage.