Question

How do capacitors effect power factor?

Answer 1

By changing the total reactance of a circuit.

Explanation:

The Power Factor is the cos `phi` , the angle between Resistance (R) and impedance (Z) or the angle between the voltage (v) and the current (i).

Supose you have an R-L series circuit, as in the figure 1 below:

The impedance Z is the vectorial sum betweem R and XL (inductive reactance), as shown in Figure 2. The angle `phi` is also showed.

Now, we introduce a capacitor in the circuit (Figure 3). The capacitive reactance is opposite to the inductive reactance and the total reactance is the difference (XT = XL-XC) and the impedance will be the vectorial sum between the resistance R and the total reactance (Figure 4).

Once XT < XL, the angle `phi` is now smaller and `cos(phi)` (Power Factor) will be higer.