Power Factor basic

 Power Factor Fundamentals

Most Industrial loads require both Real power and Reactive power to produce useful work

You pay for BOTH types of power

Capacitors can supply the REACTIVE power thus the utility doesn’t need to

Capacitors save you money!

Why Apply PFC’s?

Power Factor Correction Saves Money!

Reduces Power Bills

Reduces I2R losses in conductors

Reduces loading on transformers

Improves voltage drop

What is PF ?

Introduction:

Most plant loads are Inductive and require a magnetic field to operate:

- Motors

- Transformers

- Florescent lighting

The magnetic field is necessary, but produces no useful work

The utility must supply the power to produce the magnetic field and the power to produce the useful work: You pay for all of it!

These two types of current are the ACTIVE and REACTIVE components

The Basics:

The Power Triangle:

You pay for fuel for the VERTICAL portion of flight, as well as the fuel for the HORIZONTAL portion of flight

Similarly, motors require REACTIVE power to set up the magnetic field while the ACTIVE power produces the useful work (shaft horsepower). Total Power is the vector sum of the two & represents what you pay for:

The Power Triangle:

Power Factor is the ratio of Active Power to Total Power:

Power Factor = Active (Real) Power /Total Power

                      = kW / kVA

                      =  cos(φ)

 Power Factor is a measure of efficiency (Output/Input)

Why do we Install Capacitors?

Capacitors supply, for free, the reactive energy required by inductive loads.

You only have to pay for the capacitor !

Since the utility doesn’t supply it (kVAR), you don’t pay for it!

Utility Supplies Reactive Current

Capacitor Supplies Reactive Current

Other Benefits:

1- Released system capacity:

The effect of PF on current drawn is shown below:

Decreasing size of conductors required to carry the same 100kW load at P.F. ranging from 70% to 100%

2- Reduced Power Losses:

- As current flows through conductors, the conductors heat. This heating is power loss.

- Power loss is proportional to current squared (PLoss=I2 R).

- Current is proportional to P.F.

- Conductor loss can account for as much as 2-5% of total load

3- Capacitors can reduce losses by 1-2% of the total load

4- Voltage Improvement:

- When capacitors are added, voltage will increase

- Typically only a few percent

- Not a significant economic or system benefit

Severe over-correction (P.F.>1) will cause a voltage rise that can damage insulation & equipment; or result
in utility surcharges!

- Usually a result of large fixed capacitors at mains

Summary of Benefits:

1- Reduced Power Costs:

- Since Capacitors supply reactive power, you don’t pay the utility for it

- You can calculate the savings

2- Off-load transformers

- Defer buying a larger transformer when adding loads

3- Reduce voltage drop at loads

- Only if capacitors are applied at loads

- (minimal benefit at best)

What we learned : 

1- Most Industrial loads (i.e. motors)are Inductive and draw REACTIVE power

2- The Utility supplies this energy therefore you pay for it

3- Power Factor Capacitors supply REACTIVE energy thus the utility doesn’t need to

4- Power Factor Capacitors save money

5- There are other benefits to correcting power factor,

6- reduced heating in cables

7- reduced heating in transformer(s)

8- frees up system capacity