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How do the fan capacitor work?

01.16.2013 in Blog by admin

The fan capacitor works is not complicated. His working principle is the use of the capacitive reactance of the capacitor at a certain frequency AC signal generated to limit the maximum working current.

For example, in the 50Hz frequency conditions, a 1uF capacitor capacitance of about 3180 ohms. When both ends of the 220V AC voltage applied to the capacitor, the maximum current flowing through the capacitor is about 70mA. Although the current flowing through the capacitor 70mA, but does not generate power on the capacitor should be as if the capacitor is an ideal capacitor, the flow of current through the capacitor current is the imaginary part, which made ​​reactive for the reactive power. According to this feature, a 1uF capacitor in series with a resistive element, the resistive element at both ends of the obtained voltage and the power generated is entirely dependent on the characteristics of the resistive element.

For example, we will be a 110V/8W light bulb with a 1uF capacitor in series, received 220V/50Hz AC voltage, the lamp is lit, issued normal brightness without being burned. Because the the desired current 110V/8W bulb 8W/110V = 72mA, it 1uF capacitor generated by current limiting characteristics coincide. Similarly, we can 5W/65V bulb with 1uF capacitor in series received 220V/50Hz AC bulbs will also be lit, and will not be burned. Because the bulb 5W/65V current is about 70mA. Therefore, the capacitor buck actually using capacitance current limit. While the capacitor is actually play a limited role of the voltage across the capacitor and the load current and dynamic allocation.

fan capacitor should pay attention to the following points:
1).In accordance with the current size of the load and the operating frequency of the alternating current by selecting the appropriate capacitance, not according to the load voltage and power.
2).limiting capacitor polarity capacitor must be used absolutely can not use electrolytic capacitors. And the capacitor voltage is required more than 400V. Ideal capacitance for Tieke oil immersed capacitance.
3). capacitor buck can not be used in high-power conditions, because of insecurity.
4). capacitive buck is not suitable for dynamic load conditions.
5). the capacitor buck not suitable for capacitive and inductive load.
6). DC work is needed, try using a half-wave rectifier. Does not recommend the use of bridge rectifier. But also to satisfy the conditions of a constant load.

Tags: fan capacitor, motor run capacitor