Typical Power Factors for Common Electrical Loads

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Power factor is very critical for calculating or measuring the electrical power consumed by an electrical device on an alternating current supply. To be able to determine electrical power on alternating current (AC) systems, you need to know the power factor of the electrical load. Below is listed the  typical power factors for common electrical loads:

Electrical Load	Power Factor (CosՓ)	Reactive Demand Factor (TanՓ)
Transformers (No load condition)	0.1 - 0.15	9.9 - 6.6
Motor (Full load)	0.7 - 0.85	1.0 - 0.62
Motor (No load)	0.15	6.6
Metal Working Apparatuses:
Arc Welding	0.35 - 0.6	2.7 - 1.3
Arc Welding  Compensated	0.7 - 0.8	1.0 - 0.75
Resistance Welding	0.4 - 0.6	2.3 - 1.3
Arc Melting Furnance	0.75 - 0.9	0.9 - 0.5
Fluorescent Lamps:
Compensated	0.9	0.5
Uncompensated	0.4 - 0.6	2.3 - 1.3
Mercury Vapor Lamps	0.5	1.7
Sodium Vapor Lamps	0.65 - 0.75	1.2 - 0.9
AC DC Converters	0.6 - 0.95	1.3 - 0.3
DC Drives	0.4 - 0.75	2.3 - 0.9
AC Drives	0.95 - 0.97	0.33 - 0.25
Resistive Load	1	0

Power Factor Improvement With Capacitors

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As we have already seen in the basics of power factor in electrical distribution system, most Industrial loads require both Real power and Reactive power to produce useful work. Typically, inductive loads (motors, transformers etc) require two kinds of power to operate:

(1) Active Power (KW) – This actually performs the useful work

(2) Reactive Power(KVAR) – This helps to maintain the electromagnetic field. 

The vector sum of the active power and the reactive power gives total power often referred to as apparent power in KVA:
KVA = KW + KVA (vector sum)

Low power factor in an electrical system often occur when inductive loads are operated below their full load capacity especially motors. Consistently operating electrical loads at low power factor will result in higher utility bills because of the poor utilization of electrical energy. In fact, a higher power factor means less KVA and KVAR components and a more efficient utilization of electrical energy while a low power factor implies the presence of more KVA and reactive (KVAR) power components and less efficient electrical energy utilization:

How to Improve the Power Factor of an Electrical Distribution System

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One of the most effect ways to improve the power factor of the electrical distribution system is to install equipment that have the ability to decrease the reactive component of the power supplied by the utility company. One of such equipment is the Capacitor. Other equipment with the same ability to decrease reactive power includes:

Capacitors

Synchronous motors

Synchronous generators

We can reduce reactive power and increase power factor in an electrical distribution system by the following method:

Why You Need Power Factor Improvement

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In a typical industrial plant, AC induction motors constitute a large portion of the equipment. Since induction motors are mainly inductive loads, they are likely to lead to a low power factor. Some of the benefits of improving your power factor include:

Lower Utility Fees

Inductive loads, which require reactive power, are the main cause of a low power factor. This increase in required reactive power (KVAR) causes an increase in required apparent power (KVA), which is what the utility company supplies to your facility

So, a facility’s low power factor causes the electricity company to have to increase its generation and transmission capacity in order to handle this extra demand. By lowering your power factor, you use less KVAR. This results in less KW, which equates to a dollar savings from the utility company. Also note that a utility company will charge any consumer whose power factor is less than 0.95 an additional fee. If you reduce power factor you can avoid this additional fee.

The Basics of Power Factor in Electrical Distribution Systems

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In AC circuits, power is utilized in two basic forms: Active or Useful power measured in KW and Reactive power measured in KWAR. Before we get to understanding the concept of power factor, let us define the terms measured above:

Active Power

This is the useful working Power (also called Actual Power or Real Power). It is the power that actually powers the equipment and performs useful work. This power is measured in KW.

Reactive Power

It is the power that magnetic equipment (transformer, motor and relay) needs to produce the magnetizing flux.

Apparent Power

It is the vectorial summation of KVAR and KW. It is measured in KVA. So vectorially,

KVA = KW + KVAR