What should you pay attention to when working with a long-life electrolytic capacitor?
Article Source：QUNIO ELECTRONICS
time visited：
issuing time：2019-04-11
At a power frequency of 50 Hz, a 1 uF capacitor produces a capacitive reactance of approximately 3180 ohms. When an AC voltage of 220V is applied across the capacitor, the maximum current flowing through the capacitor is approximately 70 mA. Although the current flowing through the capacitor is 70 mA, there is no power consumption on the capacitor. If the capacitor is an ideal capacitor, the current flowing through the capacitor is the imaginary current, and the work done is reactive power.
According to this feature, if we connect a resistive component in series with a 1uF capacitor, the voltage obtained across the resistive component and the power dissipation it generates depends entirely on the characteristics of the resistive component. For example, we connect a 110V/8W bulb in series with a 1uF capacitor. When connected to an AC voltage of 220V/50Hz, the bulb is illuminated and emits normal brightness without being burned. Because the 110V/8W bulb requires 8W/110V=72mA, it matches the current limiting characteristics of the 1uF capacitor.
Similarly, we can also connect a 5W/65V bulb and a 1uF capacitor to a 220V/50Hz AC. The bulb will also be lit without being burned. Because the 5W/65V bulb also has an operating current of about 70mA. Therefore, the capacitor buck is actually using the capacitive reactance current limit. The capacitor actually acts as a limiting current and dynamically distributing the voltage across the capacitor and the load.
Pay attention to the following points when using capacitor step-down:
1、Select the appropriate capacitor based on the current of the load and the operating frequency of the AC, not the voltage and power of the load.
2、Current-limiting capacitors must use non-polar capacitors, and electrolytic capacitors must never be used. Moreover, the withstand voltage of the capacitor must be above 400V. The most ideal capacitor is an iron-shell oil-immersed capacitor.
3、Capacitor bucking cannot be used for high power conditions because it is not safe.
4、Capacitor buck is not suitable for dynamic load conditions.
5、Similarly, capacitor buck is not suitable for capacitive and inductive loads.
6、When DC operation is required, half-wave rectification is used as much as possible. Bridge rectification is not recommended. And to meet the conditions of a constant load.
