Power Factor Correction

Determining the correct equipment for your installation

So what is Power Factor Correction?

The technical terms are:

“In electrical engineering, the power factor of an AC electrical power system is defined as the ratio of the real power absorbed by the load to the apparent power flowing in the circuit, and is a dimensionless number in the closed interval of −1 to 1.

A power factor of less than one indicates the voltage and current are not in phase, reducing the instantaneous product of the two.

Real power is the instantaneous product of voltage and current and represents the capacity of the electricity for performing work. Apparent power is the average product of current and voltage.

Due to energy stored in the load and returned to the source, or due to a non-linear load that distorts the wave shape of the current drawn from the source, the apparent power may be greater than the real power.

A negative power factor occurs when the device (which is normally the load) generates power, which then flows back towards the source.

In an electric power system, a load with a low power factor draws more current than a load with a high power factor for the same amount of useful power transferred.

The higher currents increase the energy lost in the distribution system, and require larger wires and other equipment.

Because of the costs of larger equipment and wasted energy, electrical utilities will usually charge a higher cost to industrial or commercial customers where there is a low power factor.

Power factor correction

This increases the power factor of a load, improving efficiency for the distribution system to which it is attached.

Linear loads with low power factor (such as induction motors) can be corrected with a passive network of capacitors or inductors.

Non-linear loads, such as rectifiers, distort the current drawn from the system. In such cases, active or passive power factor correction may be used to counteract the distortion and raise the power factor.

The devices for correction of the power factor may be at a central substation, spread out over a distribution system, or built into power-consuming equipment.”

In Wife Terms

The-director-explaining-it-to-his-wife Terms:

By testing the electrical supply with Power Factor testing equipment, we can determine the required equipment necessary for the customer’s installation.  

Basically the more motors the customer have installed the worse the power factor becomes.

The benefits of Power Factor Correction:

  1. It lowers the customer’s electricity bills.
  2. Reduces the customer’s maximum demand ( Apparent Power )
  3. Free up load on the transformer giving the customer more capacity.
  4. Reducing the volt drop on the customers supply cables and transformers.

( Ok, so the Director’s wife didn’t quite understand  point 2,3 and 4, but she understood the necessity of a lower electricity bill…)

Such systems pay themselves of usually between 3-18 months and have a life expectancy of at least 10 years. The saving can range from 10% – 30% on your electrical bills.

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