A9FC7B57d01 - Proceedings of the 9th International...

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Proceedings of the 9th International Conference on Properties and Applications of Dielectric Materials July 19-23,2009, Harbin, China Insulation Life-span Models for Electrical and Thermal Aging under Continuous High Square Impulses Voltage Cao Kaijiang *, Wu Guangning, Zhou Liren, Guo Xiaoxia, Lei Kegang, Gao Bo School of Electrical Engineering, Southwest Jiaotong University Chengdu, Sichuan Province, 610031 P. R. China *E-mail: caokaijiangckj@163.com C-5 Abstract: Stator insulation of inverter-fed motors experiences continuous impulses with significant harmonics and transients, which may result in early failure. There are many differences in insulation aging mechanism between under continuous impulses and sine waves. In order to test insulation properties under continuous impulses, a new insulation aging test system is used to simulate the aging effect of converter on the winding insulation in the inverter-fed motors. The influences of multi-stress including impulse amplitude- temperature, impulse frequency-temperature and impulse frequency-amplitude on insulation lifetime are investigated. And the test data under different conditions are analyzed by the statistic analysis method of Weibull distribution. Finally, insulation life models for multi-stress is developed based on the above test results, which is helpful for the insulation design of inverter-fed motor. Keywords: inverter-fed motor; insulation; aging; life model INTRODUCTION With the development of power electronics technology, large power high speed switch devices have been widely used in frequency conversion adjusting speed system[l]. After adopting PWM converter of high-frequency switch device, situation early insulation failure largely appears[2,3], especially the breakdown of stator winding tum to tum insulation. Therefore, research on the life-span models insulating material under high frequency pulse voltage can provide theoretical foundation for the design of inverter-fed motor insulation structure. Experimental details Electrode was designed based on IEC-343, which is made of stainless steel. It is two electrodes system which consists of upper and lower electrodes. The upper electrode is cylindrical rod appearance, and the lower electrode is a round tabular. The diameter of upper one is 6±0.02 mm and the end cornea is round arc of 1mm radius, which is used to uniform electric field. The diameter of lower one is <I>40mm. The sample was common polyimide film of which thickness was 25~m and size was 50mm x50mm. 978-1-4244-4368-0/09/$25.00 ©2009 IEEE 285 Before the experiment, pretreatment to the sample is necessary to decrease the discreteness of test data. The sample surface should be ensured that there is no external pollution and damage, and residual charge on the sample should be removed, because the residual charge has a great effect on insulation properties of thin film material. Cleaning the sample by using alcohol can basically remove the charge on the sample surface.
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A9FC7B57d01 - Proceedings of the 9th International...

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