Monthly Newsletter

THE POWER FACTOR

Just when you thought school was getting out for the holidays, we are taking you back. Since the last “Wizard of Watts” we have attended quite a few trade shows and the hot topic seems to be Power Factor Correction. 
 
What is Power Factor?

Most loads in modern electrical distribution systems are inductive.  Examples include motors, transformers, gaseous tube lighting ballasts, etc.  Inductive loads need a magnetic field to operate.

Inductive loads require two kinds of current:
Working power (kW) to perform the actual work of creating heat, light, motion, machine output, and so on.Reactive power (kVAR) to sustain the magnetic field
Working power consumes watts and can be read on a wattmeter.  It is measured in kilowatts (kW).  Reactive power doesn’t perform useful “work,” but circulates between the source (power company) and the load.  It places a heavier drain on the power source, as well as on the power source’s distribution system.  Reactive power is measured in kilovolt-amperes-reactive (kVAR).

Working power and reactive power together make up apparent power.  Apparent power is measured in kilovolt-amperes (kVA).

Power factor is the ratio of working power to apparent power.  It measures how effectively electrical power is being used.  A high power factor signals efficient utilization of electrical power, while a low power factor indicates poor utilization of electrical power.

To determine power factor (PF), divide working power (kW) by apparent power (kVA).

For example, if you had a pool pump that was operating at 10 kW and the apparent power consumed was 12.5 kVA, you would divide 10 by 12.5 and come up with a power factor of 0.80.

Should I be concerned about low power factor?

Low power factor means you’re not fully utilizing the electrical power you are paying for.

At 70% power factor, it requires 14.2 kVA to produce 10 kW. At 95% power factor, it requires only 10.5 kVA to produce 10 kW. Another way to look at it is that at 70% power factor, it takes 35% more current to do the same work.

What can you do?

Some utility bills will show you your overall power factor.  Look for KW, KVA and KVAR on your bill. Overall power factor will be KW divided by KVA.

The most effective Power Factor Correction is:
Properly sized to the equipment it is ‘correcting’. (Need Name Plate Data)Physically placed as close to the equipment as possible. (On the Motor Controller)
Look for the low hanging fruit such as pool pumps, large HVAC and refrigerating equipment to maximize your Power Factor Correction.  USG has a Technical Data Bulletin to email out. Videos on YouTube are also available.

Source:  Eaton Corporation Technical Data

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