Three-wire capacitor, applications and features!

When installing or even maintaining a ceiling fan, we can come across a 3-wire capacitor instead of a 2-wire capacitor. Do you know how to install or replace this capacitor? In this article, we will show you all the details about 3-wire capacitors. Come on, guys!

Capacitor
Even if not visually exposed, capacitors are present in various appliances, machines, electronics, etc. But what is a capacitor after all? Capacitors are reactive electronic components, which react to the passage of electrical current through the accumulation of electrical charges, thus storing electrical energy.

When connecting a capacitor to a power source, it has the same voltage as the source. When we remove the source the capacitor stops charging, and over time it starts to lose that stored energy, being able to use this energy momentarily to feed a circuit. This process is very similar to that of a battery, the difference is that the capacitor can repeat this cycle many times before it spoils, but charging and discharging much faster than batteries and the amount of energy is much less than that of a battery.

The amount of charge that the capacitor can store is called capacitance and is measured in Farad (F). Capacitance is the characteristic of a component that has the capacity to store electrical charge. There are different types of capacitors such as electrolytic, polyester, ceramic, tantalum and etc.

Electrolytic, polyester, ceramic, tantalum.
Different types of capacitors.

3-wire capacitor
A 3-wire capacitor is nothing more than a capacitor that has two capacitors within it with a common wire. In the image below we have two capacitors, a 2-wire capacitor and a 3-wire capacitor. The 2-wire capacitor has 3 microfarads and the 3-wire capacitor has 3 microfarads + 7 microfarad. What differentiates these two capacitors is that the 3-wire has two capacitors internally one of 3 microfarads and another 7 microfarads.

Internally two capacitors of 3 microfarads and another 7 microfarads.
2-wire capacitor and a 3-wire capacitor.

To better understand, see the drawing below. There are two cables at the ends and one in the middle joining the two capacitors, this makes it possible to connect these two capacitors together or separately. Red is the central cable, black and green are the end cables.

The central red, black and green are the tips.
The internal circuit of the 3-wire capacitor.

As there are two capacitors in one, we need to find out which wires are from each capacitor because we have a 3 microfarad and 7 microfarads, for that we will use a capacitor to measure and see which cable is from which capacitor.

Measuring the red cable in relation to the black cable we have approximately 3 microfarads, so this is the capacitor with the lowest capacity. Measuring the red cable in relation to the green cable we have approximately 7 microfarads, so this is the capacitor with the highest capacity.

A capacitor of 3 microfarads and 7 microfarad.
Capacitance measurement of the 3-wire capacitor.

If we measure the black cable in relation to the green one we have an association of the capacitors in series, and different from the resistors that have the resistances added when they are in series, in the capacitors the capacitance is divided. So I have to find a total capacitance that is always less than the lowest capacitance between the capacitors.

So, in this case, it has to be less than 3 microfarads and when measuring the capacitance of the black cable in relation to the green one we find approximately 2 microfarads.