Identifying & correcting poor power factor

Identifying & Correcting Poor
Power Factor
Jeff Rainey and Andre Malcolm

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Copyright © Yokogawa Meters & Instruments Corporation
Kristin Porche
Marketing Specialist
Yokogawa Corporation of America
Newnan, GA
Kristin.porche@us.yokogawa.com
770-254-0400 ext. 5656
tmi.yokogawa.com
Host & Panelist

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Jeff Rainey
Andre Malcolm
webinars@us.yokogawa.com
tmi.yokogawa.com
Presenters

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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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<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.

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■ 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?
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■ 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?
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■ 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?
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■ 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?
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■ 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?
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■ 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?
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■ 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?
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■ 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?
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■ 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.

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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

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Show Me the Savings!
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■ 6-10% on residential
■ 6-17% commercial
■ 6-40% industrial
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Questions??
<Document Number>
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Thank You
webinars@us.yokogawa.com

Identifying & correcting poor power factor

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