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Understanding Power Factor

Understanding Power Factor

What is power factor and how does it affect your facility?

What is Power Factor?

Power Factor is a measure of the efficient use of power, the ratio of the Working Power to Apparent (or Total) Power. To determine power factor (PF), divide working power (kW) by apparent power (kVA).

PF  =    kW

Power factor is a way to find out how effectively you are using your electrical power. A high power factor indicates effective utilization of electrical power, whereas low power factor signifies inefficient use of electrical power.

When you have low power factor, you are not fully employing the electrical power you are paying for. Poor power factor is costly for the utility and the end user – power system capacity is used, kW losses are increased and voltage at the load is low. Utilities often penalize customers for low power factor as an incentive to compensate for this inefficiency.

Power Factor Figure 1. Power Factor Example

Example of calculating power factor:

100 (kW)   =   0.80 (PF)
125 (kVA)

Why you should be concerned about low power factor? Apparent power, kVA, decreases as power factor increases.

Example: At 80% power factor, it requires 125 kVA to produce 100 kW. At 97% power factor, it requires only 103 kVA to produce 100 kW. Another way to look at it is that at 80% power factor, it takes 21% more current to do the same work. See Figure 1.

What is VAR?
Power Factor The foam on the top of the beer is represents VARs, which is the wasted capacity of the actual beer, the useful work or watts produced.

Active power, also called real power, is measured in Watts or kW and performs Useful Work. Electrical equipment like motors and transformers require reactive power, create a magnetic field and allow work to be performed.

This reactive power is called Volt-Amperes-Reactive or VAR. Reactive power is measured in VARs or kVARs. Working power and reactive power make up apparent power.

For example, take a mug of beer. The capacity of the mug represents apparent power (kVA), the summation of the reactive power and working power. When you have a lot of foam (kVAR) in your mug, the lower your working power (kW), which equates to lower power factor; not very efficient if you want to get your money’s worth!

Correcting Power Factor
Power Factor Consider a horse pulling a boat on a canal. The boat turns it’s rudder to stop from running into the bank. The turned rudder creates drag so less of the horse’s power is going toward moving the boat forward.

Correcting poor power factor can significantly reduce the load on transformers and conductors, allowing for facility expansion.

Buckles-Smith provides power factor correction solutions to help in maximizing the real power use in your facility. Please contact Buckles-Smith or your Account Manager for further details.

Printable Version

Buckles-Smith is an electrical distributor with multiple stocking locations throughout Northern California and the San Francisco Bay Area. Contact us today for any questions you may have and we'll help you out.

Contact Buckles-Smith      800-833-7362

Posted: Jul 31, 2014,
Categories: Clean Energy,
Comments: 4,


You've got questions, we've got solutions. With ten application engineers on staff, Buckles-Smith's Tech Blog features the latest news on industry technology and commentary from our resident experts.

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4 comments on article "Understanding Power Factor"

Jean Grimshaw, 8/14/2014 8:31 AM

Good article but needs more direct application explaination such as how to derive Power Factor elements. Is working power the specification rating? Is Working power measured or averaged real V x A measurement?

Bonneau Dickson, PE, 8/14/2014 9:03 AM

Good blog, but difficult to print.

Can you include a button to provide it in printable format?

Thea Copeland, Buckles-Smith Marketing Manager, 8/14/2014 10:30 AM

@Jean - thanks for the feedback. We are working on expanding the explanation per your recommendation.

Administrator, 8/14/2014 11:00 AM

@Bonneau - we have added a printable version of the blog, you can find it at the bottom of the post or here: http://www.buckles-smith.com/Portals/0/TechBlog/Buckles-Smith_power_factor_correction.pdf

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