Views: 1 Author: Site Editor Publish Time: 2019-09-06 Origin: Site
The ripple current of a thin film capacitor refers to the alternating current flowing into the capacitor. The reason why it is called the ripple current is because the associated AC voltage attached to the DC bias voltage of the capacitor travels like the ripple on the water. .
The ripple current causes the film capacitor to heat up, too high a temperature rise will cause the capacitor to exceed its allowable die temperature and quickly become damaged, working close to allowing the die temperature will greatly shorten the expected lifetime. The allowable ripple current is determined by how much load life is allowed and still meets the load life specifications of the film capacitor.
Temperature characteristics of ripple current: The rated ripple current will increase for operating temperature less than the rated temperature, and the increase will be shown in the specification. The general increase depends on the die temperature, rated temperature, and ambient temperature. The calculation formula is as follows: ripple temperature increment = [(die temperature - ambient temperature) / (die temperature - rated temperature)] 1/2. A high ripple current will cause the operating life to be less than the expected lifetime, because the longer the film capacitor is, the larger its equivalent series resistance will increase for the same ripple current, which will accelerate the wear of the capacitor.
Frequency characteristics of ripple current: When the operating frequency is not 120Hz, the rated ripple current should be corrected, and the increase will be shown in the technical specifications. Usually the amount of increase is determined by the equivalent series resistance expected to vary with frequency. Equivalent series resistance is a complex function of temperature, capacitance, voltage rating and frequency, so it is difficult to generate an incremental table that accurately simulates its frequency dependent ripple frequency.
