Power Factor and Harmonics

Let’s DiscussLet’s Discuss

Power Factor Correction (PFC)

DefinitionsDefinitions

Power Factor (PF):

Term used in regard to the efficiency of an electricalpower distribution system. Power factor is ameasurement between the current and voltage phase shift waveforms.

PF ComponentsPF Components

Power factor consist of 3 components:

KW, which is the working, or real, power (does the actual work) KVA, which is called the apparent power

(relationship between KW and KVAR) KVAR, or reactive power

(does not do any beneficial work)

Determine your PF

Divide the working power (KW) by the apparent power (KVA.

PF of 1, or unity, being the highest (or best)power factor possible.

When correcting PF, in general, a measurement of.9 or higher is considered good.

Industries known to have poor PF Industries known to have poor PF

Industries where power factor problems are common: Steel/Foundries Chemicals Textiles Pulp and paper processing Automotive and other automated assembly Rubber and plastics processing Breweries Electroplating

Causes of PF ProblemsCauses of PF Problems

Loads that cause power factor problems: Induction motors Electric arc furnaces Machining Stamping Welding Variable Frequency Drives (VFDs) Fluorescent lights with magnetic ballasts Computers Computer controlled equipment

Benefits of Improving PFBenefits of Improving PF

Improving PF: Lowers your electrical cost Increases KVA capacity (increase the KW

used for the same KVA) Improves voltage regulation Allows for the size reductions in cables,

transformers and switchgear Allows for expansion without additional

electrical improvements

Utility Company’s point of viewUtility Company’s point of view

Raising the average operating PF of the entire grid network from .70 to .90 means:

Reduced costs from inefficiencies

Increased generation and distribution potential

Lower demand on the grid

Better PF meansBetter PF means

Utilities can save hundreds of thousands of tons of fuel (and produce fewer emissions), have more transformers available, and reduce building new power plants and their support systems.

This is why more utility companies are starting to charge a “Power Factor Penalty” so they can recover additional cost they incur from supporting an inefficient system.

PF Improvement ExamplePF Improvement Example

Assume you have a load of 100kVA with a PF

of .80, then you have enough power to light 800

100-wattlight bulbs. If you improve the PF to .95,

you now have enough power to light 950 100-watt

light bulbs.

PF Improvement can save $PF Improvement can save $

Because power factor correction capacitors: Use less energy

Lengthen the life of equipment

Reduce electrical requirements for any new or future equipment that is installed

Utility kVA BillingUtility kVA Billing

Most utilities use the kVA billing method therefore: You are charged for the current your system draws from

the grid

Many utilities add a surcharge or adjustment for PF.

Special tariffs applied

Interruptible rates applied

Off-peak rates

Some utilities give credits or bonuses for higher than average

PF, or one that is above a predetermined level

ExampleExample

If you are using 100 kW and have a PF of .70, then improve it to .95 it would result in a savings of 37 kVA usage:

100 kW at .70 PF = 142 kVA 100 kW at .95 PF = 105 kVA Reduction of 37 kVA

Using the previous example, if you are billed at $11.22 per kVA:

100kW @ .70 PF = 142 kVA, or $1,593 100kW @ .95 PF = 105 kVA, or $1,178

This represents a monthly savings of $415, or $4,980 annually. Assuming the equipment cost was $5,600 the ROI would be about 14 months. After this period there can be an ongoing 26%savings.

Return on Investment (ROI)Return on Investment (ROI)

A capacitor’s function is to: Provide kilovars to a system at the point of connection Improve PF Reduce lagging components on the circuit Reduce power losses Reduce kVA load. Provide reactive power to replace the VARs wasted by an

inefficient load

PF Correction CapacitorsPF Correction Capacitors

Are the most economical means of improving PFbecause of their:

Relative Low Cost Easy Installation Low Installation Cost Minimal Maintenance High Efficiency and Low Losses

PF Correction CapacitorsPF Correction Capacitors

Find poor PF problems by: Monitoring at the incoming service entrance or at specific

loads can identify problems within a facility Conduct a Facility Power Study and have reviewed by a

power analyst / consultant

Some utilities offer analysis for businesses wanting toimprove their efficiency.

Determining the PFDetermining the PF

Simple small fixed capacitors can be installed at a single motor to be switched on and off with the load, this is ideal.

However, this can be expensive, and can create technical problems, since it may require a large number of low-power units at several points throughout the facility, making it difficult to monitor and maintain over time

Types of Capacitor SystemsTypes of Capacitor Systems

Types of Capacitor SystemsTypes of Capacitor Systems

Automatic capacitor bank installed on the bus bars of the distribution panel. This method provides centralized PF correction for an entire facility.

It also allows for fixed capacitors to be added to correct the power of any piece of equipment that causes a significant problem.

Installation Locations Installation Locations

Next Step - Determine the kVARNext Step - Determine the kVAR

After you have determined what type capacitor system you need, the next step is to determine the size or amount of kVAR, you need to correctthe PF.Staco Energy Products Co. has easy to usetables that will assist you in determining therequired kVAR you need to add to your systemto improve the PF.

Next StepNext Step

Example: If your existing PF is .71 and you want to bring it up to .95, the number in the table is .663 (kW multiplier).

Multiply .663 by the number of kW your system uses (say 590). The total kVAR would require 390 kVAR, which would be rounded up to 400 kVAR. Therefore a 400kVAr rated unit would be used.

Final StepFinal Step

Purchase a StacoAutomatic Switched400 kVAR StacoVARSystem, OF COURSE!

Fixed Capacitor AssembliesFixed Capacitor Assemblies

Fixed capacitor assemblies, also called motor loadcapacitors, are ideal for improving PF whereinduction motors are located. They are also usedanywhere there are small kVAR requirements. You can achieve maximum benefits from capacitorswhen located at the load. Because the capacitor isUsually switched on and off with the load, overcorrection is also avoided

Sizing Fixed Capacitors Sizing Fixed Capacitors

Capacitors must be carefully sized when switchedwith the motor as a unit, because:

Dangerous over voltages and transient torques can occur if the kVAR exceeds the motor’s magnetizing current

What you need to know! What you need to know!

When sizing fixed capacitors you need the followingMotor information:

U-Frame (U, T etc.) NEMA Class (B, 2B, C, D etc.) A or B Normal Starting Torque – Normal Running Current

Installation Locations Installation Locations

1. Motor Side of Overload Relay Use this for new motor installations where overloads can be

sized in reference to reduced current draw Existing motors where no overload change is needed

2. Motor Side of Starter Use this for existing motors when the overload rating

exceeds code 3. Line Side of Starter

Use this for Multi-speed motors Motors that are jogged or reversed Motors that star frequently Starters that disconnect/reconnect capacitors during cycle

and starters with open transitions High inertia loads, when disconnecting the motor with the

capacitor turns the motor into a self-exciting generator

Installation Locations Installation Locations

Motor Reference Tables Motor Reference Tables

Staco Energy Products Co. has all the referencetables available to make it easier to select andsize the correct StacoVAR Motor Load Capacitorfor your application.