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Motor Power FactoEnergy conservation is a hot topic twaste of electrical energy. Many qucompetitors stress the high power fInduction motors are only one of thfactor. And it's the overall plant systsystem power factor, so maximumthe better way.A Quick Review of the Theory True Power , measured in watts (Wdoes useful work.Reactive Power , measured in volt-inductive motors, transformers andApparent Power , measured in voltcurrent that flows in it. It is the vectPower Factor , is the ratio of the trusource. It 's usually expressed in pevector diagram is a measure of p

Only the true power (W) in a systereally flows: The apparent power (Vplant's overall power factor and it'splant, the power distribution system

just useful watts. In short, the differpower factor, represents power thatWhy Not High Motor Power FactoAs the diagram indicates, if the VAmotors with high power factor will hvector. But... First: Motor load may

1. Motor load is relatively smasuch equipment as plant lig

2. Most of the induction motorinherently high, and the po

3. The plant uses some synchdiagram, they tend to decre

4. Motors are only part of the iAlmost any plant has someoperated mechanisms, and

plant's wiring and in theory5. High motor power factor isthe time at reduced load.

In the above situations a high motonot enough to justify the cost and otSecond: You don't get as good a mdesigner has to consider a numberefficiency, as well as power factor,power factor and high efficiency intsuch as a reduced air gap, actually

and Energy Conservationese days and everybody "knows" that low power fa

estions are asked about the power factor of inductioctor of their motors. Why don't we?kinds of electrical equipment that tend to reduce a

em's power factor that counts. There are ways of co otor power factor isn't vital. System power factor c

), is the power, drawn by the electrical resistance of

amperes, reactive, (VAR) is the power stored in andsolenoids all draw reactive power.amperes (VA) is the voltage on an AC system multir sum of the true and the reactive power.e power used in a system to the apparent power drcent: W/VA x 100. The cosine of the angle betweenwer factor. The larger the VAR current the lower th

does useful work. But the utility has to generate anA). Utilities usually only meter watts, but a utility canommon to charge a rate penalty if that power factoalso has to be sized to distribute and switch the apnce between useful power and apparent power, asdoes no work but costs the user MONEY .r? vector is short, the power factor will be high. So itlp, because they will contribute less to the overall sot have much effect on system power factor. This i

ll in comparison to resistance load (W) on the planthting and resistance heating.load is represented by large, high-speed motors. Ter factor of the fewer small motors won't mean mu

ronous motors. These don't increase the VAR vectoase it.nductive load responsible for the length of the diagrpower transformers probably welding transformers,induction heating equipment. Also there is "stray in

these wiring systems are pure resistance loads.asted if the motor is oversized for the driven load,

power factor won't affect overall system power facther disadvantages of motors designed for maximuotor design by concentrating on high power factor.of parameters such as temperature rise, torque chand he can't optimize them all. It's costly to try to dea motor, and some of the design changes that imp

have the opposite effect on efficiency.

ctor can meann motors. Some

plant's powerrrecting a lowrrection is often

a system, that

discharged by the

plied by all the

wn from theVA and W in thispower factor.

d distribute whatmeasure ais low. Within thearent power, notindicated by

ight seem thatystem VAR

true when:

ystem, drawn by

eir power factor ish.r shown in the

m's VAR vector.possible solenoid-

uctance", in the

r runs much of

or much. Probablypower factor.he motoracteristics andign both high

rove power factor,

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The Better Way No matter what motors do to a planThe VAR vector in the diagram aboreactance, which produces an opporeactance, they tend to cancel eachalmost as great as inductive VAR's

factor -- is high.

How: Sometimes rotating capacitors arecapacitors are more common. Mayeach several plant load centers. Or,approaches is best for a given plantmake general recommendations. Afor detailed information and expertTo Sum Up Now you see why we don't go the hdesirable characteristics have to bethe motor -- to get their effect. But twhatever extent it has an effect, capower factor to 95-98%, a greater ihas the big advantage of correctingalso tend to lower the power factor.match a utility's billing structure, sowill really save MONEY .

system power factor, it can be corrected, and that'e represents inductive reactance. But there's also

site VAR vector. If a system is being affected by botother. In the system vector diagram below, capaciti

so W more nearly equals VA, and W/VA x 100 -- th

sed to put capacitive reactance into a plant system,e one central bank to correct the entire plant systean individual capacitor installation at each motor.requires analysis of many variables, and we are no

customer in doubt should contact the major capacitdvice.

ighest-power-factor routed in motor design. Efficiendesigned into the motor, because there's no goode effect of motor power factor on plant system powbe compensated for by external means and capaciprovement than can be designed into a motor. Ext

for the transformers and other equipment on the plWith capacitors, a facility's system power factor canthat the facility pays only for the degree power facto

the better way.apacitiveh kinds ofve VAR's aresystem power

but static, or a bank athich of these

t in a position tor manufacturers

y and otheray -- external tor factor, to

tors can improvernal correctionnt system thatbe "tailored" to

r corrections that