identifying & correcting poor power factor

Identifying & Correcting Poor Power Factor Jeff Rainey and Andre Malcolm

2 Copyright © Yokogawa Meters & Instruments Corporation

Kristin Porche Marketing Specialist Yokogawa Corporation of America Newnan, GA [email protected] 770-254-0400 ext. 5656 tmi.yokogawa.com

Host & Panelist


Jeff Rainey Andre Malcolm [email protected] tmi.yokogawa.com

Presenters


Topics

<October 2015> Copyright © Yokogawa Meters & Instruments Corporation

What is Power Factor? What are the causes for Low Power Factor? Why do we need to improve Power Factor? How do we correct Power Factor? What are the benefits of corrected Power Factor? What tools are required to accurately measure and calculate?

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What is Power Factor?

<Document Number> Copyright © Yokogawa Electric Corporation

Before we begin let’s look at a few basic terms

■ KW = Real or Actual Power. This does the actual work

■ KVA = Apparent Power. It is the calculated RMS current times the RMS voltage

■ KVAR = Reactive Power. Occurs in an AC system when voltage and current are not in phase

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■ Power Factor is the ratio of Real Power divided by Apparent Power

Here’s a good analogy…

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■ Thus, for a given KVA: The more foam you have (the higher the percentage of KVAR), the lower your ratio of KW (beer) to KVA (beer plus foam). Thus, the lower your power factor. The less foam you have (the lower the percentage of KVAR), the higher your ratio of KW (beer) to KVA (beer plus foam). In fact, as your foam (or KVAR) approaches zero, your power factor approaches 1.0.

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■ The Power triangle illustrates the relationship between all four

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Power Factor is the ratio Between impedance and Resistance.




■ In a perfect world KW and KVA would be almost equal, thus the angle would approach zero so the power factor would be close to 1.

To have an efficient power system we want our power factor to be as close to 1 as possible.

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What Causes Low Power Factor?


■ Since we define power factor as the ratio of KW to KVA we see that low power factor results are when KVA is higher. ■ Higher KVA is caused by inductive loads.

■ Inductive loads occur when the current waveform lags the voltage

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■ Prime examples of Inductive loads include the following:

Induction Motors Transformers Induction generators (wind mill generators) High Intensity Discharge (HID) lighting

All of these examples consume the largest amount of energy in industrial complexes.

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■ Capacitive loads occur when the current leads the voltage

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■ Examples of capacitive loads would be: Incandescent light bulb Synchronous motors Heater

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Why Try to Improve?


■ Lower Utility fees Remember that inductive loads, which require reactive power, causes our

low power factor. The increased demand for reactive power increases our need for KVA which is supplied by the utility. By raising our power factor we use much less KVAR. When we use less KVAR we use less KW which saves us a lot of money from the utility.

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Why Try to Improve?


■ Eliminate Power Factor penalty. Some utilities charge a surcharge for poor power quality. In many cases, utilities charge extra for power quality below 0.95. Some utilities will not and are not obligated to deliver power to customers with power factors below 0.85

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Why Try to Improve?


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Why Try to Improve?


■ Increase System Capacity and reduce system losses by adding capacitors to your system.

Capacitors are basically KVAR generators.

By adding capacitors to the system, the power factor is improved and the KW capacity of the system is increased. With lower system losses in your power system you can add much more load at the same KVA cost.

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Why Try to Improve?


■ Low voltage levels in your electrical system cause overheating and premature failures in motors and other inductive equipment

■ By increasing power factor you will eliminate many voltage drops in feeder cables and other related equipment.

■ Motors will run much cooler and much more efficient. You should also see a slight increase in starting torque and capacity.

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How to Correct?


■ Installing capacitors (KVAR generators) decreases the magnitude of reactive power, thus increasing your power factor.

■ Reactive power (KVARS), which are caused by inductive loads always work at a 90 degree angle to working power(KW).

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How to Correct?


■ Inductance and capacitance react 180 degrees to each other ■ Capacitors store KVARS and release energy opposing the reactive energy

caused by the inductor. ■ By having both a capacitor and an inductor in the same circuit, the

systems constantly alternate the transfer of energy between the two resulting in a balanced system.

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How to Correct?


■ Avoid running motors at a lightly loaded condition. This lowers power factor immensely.

■ Avoid operating equipment above it’s rated voltage ■ Replace older standard motors with energy efficient ones as they burn out.

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How to Correct?


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What Do I Need?


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Choosing an energy monitoring device like the Yokogawa CW500 that has the ability to measure power factor and calculate capacitance correction is important in gaining an accurate overall picture of energy usage and planning efficiency measures.


What Do I Need?


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The CW500 also has the capability to Calculate power factor correction Capacitance.

Target Power Factor Set the power factor when phase advance capacitors are installed. The power factor degrades if inductive loads, such as motors, are connected to the power supply because current phases lag behind the voltage phases. Usually, phase advance capacitors are installed in high- voltage – receiving installations, to improve its situation


Show Me the Savings!


■ 6-10% on residential

■ 6-17% commercial ■ 6-40% industrial

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Questions??


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Thank You

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identifying & correcting poor power factor

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