Interturn Insulation Quality Assessment, Considering the Standards State
Usage of drive fed induction motors due to numerous and considerable industrial benefits of this kind of electrical machines are obviously increasing. On the other hand, voltage distribution in stator winding of drive fed induction motors is not completely predictable. Non uniform voltage distribution results from the short rise time surges which arise from electrical drives. According to the published reports and papers, interturn insulation deterioration due to non-uniform voltage distribution constitutes one of the main parts of the stator insulation failures. This issue could be potentially considered as a source of unscheduled shutdowns in the industries and consequently big financial losses.
In order to assess the suitability and condition of interturn insulation, test methods have been suggested by IEC/TS 60034-18-42:2008 (or DIN EN 600034-18-42 draft in April 2013). However this publication is to general and there is no specific data to implementation the test. For instance it is possible that the same test with the same material has been done by two different testing laboratories, by the time the achieved results are different.
In this research, in accordance with the IEC/TS 60034-18-42:2008 (or DIN EN 600034-18-42 draft in April 2013), the interturn insulation for samples with different insulation structures and copper strand thicknesses and length have been tested. Additionally, the lifetime test with high frequency impulse voltages has been done on the samples. At the end, the achieved results from partial discharge tests and also lifetime tests have been analyzed and compared. In order to have a proper and accurate comparison, the copper strand thicknesses and differences in the insulation structures and other criteria have been completely considered in the analysis.
Finally, in order to have a proper assessment of the interturn insulation condition, it has been tried to introduce an optimum insulation structure with the most stable and independent results. It could be really applicable to judge interturn insulation correctly and choose a proper insulation material for induction drive fed motors and increase the reliability of drive fed induction motors.