Power Systems

How to calculate the Power Factor Correction

Let us consider an inductive load taking a lagging current I at a power factor cosΦ1. For us to improve the power factor of such a circuit, the solution is to connect equipment in parallel with the load which takes a leading reactive component and partly cancels the lagging reactive component of the load. Figure 1.0 below shows a capacitor connected across the load.

A capacitor connected across the load
Figure 1.0 A capacitor connected across the load

The capacitor takes a current IC which leads the supply voltage V by 90°. The current IC partly cancels the lagging reactive component of the load current as demonstrated in the phasor diagram in Figure 1.1. The resultant circuit current becomes I’ and its angle of lag is Φ2. It is clear that Φ2 is less than Φ1 so that the new power factor cosΦ2 is more than the preceding power factor cosΦ1.

Figure 1.1 Phasor diagram

From the phasor diagram, we can clearly see that, after the power factor correction, the lagging reactive component of the load is reduced by I’ sin Φ2.

In other words,

I’ sin Φ2 = I sin Φ1 – IC

IC = I sinΦ1 – I’ sin Φ2

We know that:

            

Therefore the capacitance of the capacitor to improve the power factor from cosΦ1 to cosΦ2is:

Also Read: Power Measurement in AC Circuits (Single-phase & Polyphase Systems)

Power Factor Correction Demonstration Using a Power Triangle

Let’s consider Figure 1.3 below:

Figure 1.3 Power triangle

The power triangle OAB is for the power factor cos Φ1, whereas power triangle OAC is for the improved power factor cos Φ2. Though the active power (OA) can be seen not to change with the power factor improvement, the lagging kVAR of the load is reduced by the power factor correction equipment, hence improving the power factor to cosΦ2.

The leading kVAR supplied by power factor correction equipment

BC = AB – AC                  

Don’t miss out on key updates, join our newsletter  List

= kVAR1 – kVAR2

= OA (tan Φ1 – tan Φ2)

= kW (tan Φ1 – tan Φ2)

Therefore, if we know the leading kVAR supplied by the power factor correction equipment, the appropriate results can be achieved.

Also Read: AC Circuits with Resistors, Inductors and Capacitors

John Mulindi

John Mulindi is an Industrial Instrumentation and Control Professional with a wide range of experience in electrical and electronics, process measurement, control systems and automation. In free time he spends time reading, taking adventure walks and watching football.

Recent Posts

Standard Process Signals for Industrial Instrumentation

Industrial measurement and control processes employ standard process signals that are used throughout all the…

1 week ago

Top 5 Benefits of Combining CCTV Cameras with Biometric Systems

The integration of advanced technologies in security systems has become imperative for ensuring safety and…

2 weeks ago

Sources of Power Quality Problems

Power quality may be affected by a number of issues. Our discussion in this article…

2 weeks ago

Common Terms Used When Describing Power Quality Problems

Power quality has become an important issue to electricity consumers at all levels of consumption.…

2 weeks ago

What to Expect from PCB Assembly Services in China

The importance of printed circuit board (PCB) technology has escalated throughout the years with the…

2 weeks ago

Magneto-Optic Current Sensors for High Voltage, High Power Transmission Lines

One of the key challenges in measuring the electrical current in high voltage, high power…

3 weeks ago