Power Factor Fundamentals
What we will learn:
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:
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 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!
Other Benefits:
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%
Other Benefits:
Reduced Power Losses:
- As current flows through conductors, the conductors heat. This heating is power loss
- Power loss is proportional to current squared (PLoss=I2R)
- Current is proportional to P.F.:
- Conductor loss can account for as much as 2-5% of total load
Capacitors can reduce losses by 1-2% of the total load
Other Benefits:
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:
Reduced Power Costs:
» Since Capacitors supply reactive power, you don’t pay the utility for it
» You can calculate the savings
Off-load transformers
» Defer buying a larger transformer when adding loads
Reduce voltage drop at loads
» Only if capacitors are applied at loads
» (minimal benefit at best)
What we learned..
Most Industrial loads (i.e. motors)are Inductive and draw REACTIVE power, The Utility supplies this energy therefore you pay for it Power Factor Capacitors supply REACTIVE energy thus the utility doesn’t need to Power Factor Capacitors save money There are other benefits to correcting power factor,
- reduced heating in cables
- reduced heating in transformer(s)
- frees up system capacity