Voltage Distribution Of High-voltage Capacitors

When the internal components of the capacitor are in parallel structure, there is no problem of different voltage distribution. However, the internal components are capacitors with a series structure. If DC and AC voltages are applied, the voltages distributed on the internal components are different. The application of AC voltage will generate an AC current i on the element, then the voltage u on each element is the product of i and its capacitive reactance: U = i * 1 / WC.

When a DC voltage is applied to a high-voltage capacitor, a steady-state DC leakage current will be generated after the charge is saturated. The voltage of each element is the product of the resistance and the leakage current. That is, the voltage is distributed according to the insulation resistance value of the internal components. Generally speaking, in the production process of high-voltage capacitors, the error of the capacitance C of the components connected in series is very small, and the insulation barrier is greatly affected by the factory environment, and the individual error is relatively large. In other words, it is an ideal test method to distribute the voltage according to the capacitance value C.

According to the insulation resistance distribution, the insulation resistance of the good components is relatively large, and the insulation resistance of the components that withstand most voltage problems is small, and they only withstand less voltage, which cannot guarantee the detection of internal high-voltage electrical problems. Therefore, it is generally believed that the DC withstand voltage test may cause an unreasonable voltage distribution of the internal series components compared to the AC withstand voltage test.