1) capacitance value and allowable deviation
The capacitance of electrolytic capacitor depends on the impedance when working under AC voltage. Therefore, the capacitance value, that is, the AC capacitance value, changes with the change of working frequency, voltage and measurement method.
According to JISC 5 102 standard, the measurement conditions of aluminum electrolytic capacitor capacitance are frequency 120Hz, maximum AC voltage 0.5Vrms, DC bias1.5 ~ 2.0V. It can be asserted that the capacity of aluminum electrolytic capacitor decreases with the increase of frequency.
2) Rated voltage
Within the specified ambient temperature range, the series value of the highest DC working voltage that the capacitor can withstand is called rated voltage. Although the rated voltage is not a measurement parameter to measure the capacitor, the working voltage applied to the capacitor is closely related to it, and it is generally stipulated that it should be lower than the rated voltage. Reducing the applied voltage has a significant effect on improving the service life of the product.
3) Tangent value of loss angle
In an AC circuit, the actual capacitance must consume a small part of the useful signal power. Under the sine voltage with specified frequency, the ratio of consumed active power to reactive power is called loss tangent, which is about 0.0 1 to 0.20, but it varies with the type of electrolytic capacitor, capacitance size and rated voltage, and is closely related to temperature and frequency. Sometimes expressed as a percentage.
4) Impedance
At a specific frequency, the resistance that hinders the passage of AC current is called impedance (z). It is closely related to the capacitance and inductance in the capacitance equivalent circuit, and also related to ESR.
In the low frequency range, the capacitive reactance (XC) of the capacitor gradually decreases with the increase of frequency, and when the frequency continues to increase to the intermediate frequency range, the reactance (XL) decreases to the value of ESR. When the frequency reaches the high frequency range, the inductive reactance (XL) becomes dominant, so the impedance increases with the increase of frequency.
5) Leakage current
The dielectric of the capacitor has a great obstacle to DC current. However, because the alumina film medium is immersed in electrolyte, when voltage is applied, a small current called leakage current will be generated when the oxide film is reformed and repaired. Generally speaking, the leakage current will increase with the increase of temperature and voltage.
6) ripple current and ripple voltage
In some data, they are called "ripple current" and "ripple voltage", which means the ripple current/voltage value that the capacitor can tolerate. When the ripple current increases, the ripple voltage will increase exponentially even if the ESR remains unchanged.
In other words, when the ripple voltage increases, the ripple current will also increase, which is why the capacitor is required to have a lower ESR value. After adding ripple current, the equivalent series resistance (ESR) inside the capacitor generates heat, which affects the service life of the capacitor. Generally speaking, the ripple current is proportional to the frequency, so the ripple current is relatively low at low frequencies.