Prequalification of Capacitors for High-Precision Voltage Dividers

<strong>To ensure long-term stability, it is very important to prequalify capacitors used in high-precision voltage dividers. This paper analyzes how film and foil capacitors change due to charge and discharge cycles under different test conditions. The presented experiments aimed at simulating the electric stress associated with high voltage tests in a laboratory. The test procedure considers parameters like magnitude of test voltage, number of impulses, series resistor, test circuit geometry, cooling, self-heating, and temperature. The results indicate that with a variation of up to 500 ppm the change of capacitance caused by repetitive impulse stress can be significant. However, this effect will be smaller when there is natural cooling between test cycles. In this case, the best-suited capacitors showed a variation of less than 200 ppm. In addition, the comparison of different tests shows that the temperature coefficient plays a significant role in the change of capacitance. During the whole test, some of the capacitors show non-recoverable damage. The prequalification testing identified a suitable type of capacitor, which will be used for the realization of a high-precision RCR divider in the European research project “HV-com²”.</strong>

为保障长期稳定性，对高精度电压分压器所用电容器开展预合格性验证至关重要。本文分析了薄膜箔式电容器在不同试验条件下因充放电循环产生的性能变化。本次开展的试验旨在模拟实验室高压试验中涉及的电应力环境。试验流程涵盖多项参数，包括试验电压幅值、冲击次数、串联电阻、试验电路几何结构、冷却方式、自热效应以及环境温度。试验结果表明，在重复性冲击应力作用下，电容器电容的变化幅度最高可达500 ppm（parts per million，百万分比），该变化较为显著。但若试验循环间采用自然冷却，则该影响会有所减弱；在此场景下，适配性最优的电容器其电容变化幅度可控制在200 ppm以内。此外，不同试验的对比结果表明，温度系数对电容变化具有显著影响。在整个试验过程中，部分电容器出现了不可逆损坏。本次预合格性试验筛选出了一款适配性良好的电容器，将用于欧洲研究项目"HV-com²"中高精度RCR分压器的研制。