In the

earlier article, we saw what power factor is and how it is calculated. Now let us see why it is necessary to control the power factor. Power Factor Control refers to the reduction of the phase angle - the angle between the current and the voltage. As the power angle reduces, the power factor which is a cosine of the phase angle increases. It becomes closer to one. In the industry, around 80% of the power is inductive. This causes the current to lag behind the voltage resulting in a power factor that is less than one.

But how does this affect the power system? To understand this, we need to look at the the formula for power.

Active power = V x I x cos φ

If we are to increase the power factor, the current for a given value of kilowatts will be less resulting in a reduced loading of the system and reduced losses. This is the reason why the power factor is increased to a value closer to one.

Thus when the value of the power factor cos φ is less, more current is required to deliver the same amount of kilowatt. This increased loss will result in copper losses or I2R losses in the system. The conductors, cables will also be subjected to higher loading as they have to carry more current.

Let us take an example, say, a single phase motor with a rating of 100kW with a supply of 440V. Running this motor at a power factor of 0.5 will result in a current of 454.5A. However, running the motor at a power factor of 0.9 will result in a 252A only.

The reduction in current required is substantial. This reduced current will also result in reduced loading of the source as power sources such as generators and transformers are rated in kVA

Power factor improvement is done by using capacitors, active power factor controllers and so on. We will discuss about them in the next article.