Define Power Factor

Ok I'll jump in here with tin hat in place and body armour.

Power factor is described as the actual power versus the indicated apparent power in watts and the calculated power P/VI. Because when AC power is measured unless the load is an exact resistive load, both inductance and capacitance can lead to false indications of power consumed against power supplied to the load. Power factor correction (usually capacitive) is applied to an inductive load to bring the voltage and current into line.

C I V I L voltage leads in a capacitive load and voltage lags with an inductive load.

It is the ratio of reactive power to resistive power. This indicates the power dissipation in an insulator or capacitor or inductor.

Come on in the waters deep.

The other post is correct but a little wordy; simply put Power factor is the angular difference between AC current and AC voltage in a circuit, it is the result of capacitance and inductance on the circuit.

Sorry friend, you are very misguided. The reply from guest # 1 is dead-on.

In a purely resistive circuit, as the AC sine wave rises, the current flow rises right with it. In a perfect inductive load, ( no such thing ), the voltage rises but the current DELAYS by 90°. ( In a 60 hz circuit, there is one complete cycle in 1/60 second which equals 360°. The positive half cycle is 1/120 second or 180° SO.... in a purely inductive circuit, the current would DELAY the voltage rise by 90° or 1/240 second. This is called phase angle or phase shift. The formula is as such: X_L = 2 ∏ *F*L where X_L is inductive reactance, 2 ∏ is 6.28, F is frequency in Hz and L is inductance in Henry's. Summary, inductance alone in a circuit, 1) opposes any change in current. 2) produces an electromagnetic field around itsdelf. 3) tends to limit AC flow in a circuit. 4) passes DC voltage without attenuation except for the resitance of the copper itself. 5) produces a phase shift of 90° with current LAGGING voltage.

Conversely, a purely REACTIVE circuit, ( PURE CAPACITANCE....no such thing ), causes the Current to rise BEFORE the voltage by...you guessed it, 90°. The formula for Capacitive reactance is 1 divided by 2 ∏ * F * C where C equals capacitance in Farads. Summary, pure capacitance in a circuit 1) opposes any change in voltage. 2) produces an electrostatic field between its plates. 3) tends to limit AC flow in a circuit. 4) blocks DC flow and 5) produces a phase shift of 90° with current LEADING voltage.

You think THAT was wordy....read on ! ( but.... it gives more background to guest # 1's original explanation.)

The only reason why the average commercial customer is concerned with power factor is that they end up paying for electric power that essentially got wasted. Lets get a serious explanation here, now that we have the basics of inductors and capacitors.

Power factor is in reality a comparison of the amount of power a circuit is apparently using versus what it is ACTUALLY using. Its often expressed as a percent. A pf of .8928 is a power factor of 89.28%. Power factor is True Power divided by Apparent Power. ( True Power = I² * R and Apparent Power = V * A ) True power ALSO = Apparent power times the power factor !

Consider an electric circuit having a pf of .5 or 50%, and a source voltage of 100 volts and an impedance of 20 Ω. Ohm's Law states that ( I = E/Z ) so 100/20 = 5 amps. Sure enough, an ammeter in the circuit will read 5 amps.

But Apparent power is the source voltage and current through the source or 100 * 5 or 500 VA

Since the true power is apparent power times pf, the load in the circuit must be receiving 100 (volts) * 5 (amps) * .5 ( pf ) or 250 watts. Now this means that the wiring must carry the current of 5 amps that's shown by the ammeter instead of 2.5 amps normally required for a pure resistive load.

The naturally inquisitive guy ( not me, I'm yawning hehe.. ) may ask.... WHY ?

The answer lies in the magnetic fields developed around the reactance of the circuit. Energy is required to build up the field of a reactance, but this energy is returned to the circuit when the field collapses. The energy is carried in the form of current from the source and is returned as current to the source. At the same time, the LOAD is constantly demanding energy and therefor current.

Now there you are...everything you ever wanted to know about power factor and are now sorry you asked !!

Well said Sniccus. And it's a really big deal for large manufacturing plants and power utilities. They are always fighting over the accuracy of the electric bill due to the type of loads. It's big money too.

PF = cos (Phi)

I'm sure you meant to say - it's the cosine of this angle.

Codey

Power factor is the ratio of real power and reactive power. In other words power factor is watts/volt-amps in a AC circuit.

When a load of some description is supplied with an AC voltage the current that flows is not just proportional to the voltage. In mathematical terms the voltage and current may be described as:

V = V₀*sin(w*t) and

I = I₀*sin(w*t-Ø)

If you calculate the average power dissipated in the load it is P = V₀*I₀*cos(Ø) and the term cos(Ø) is called the power factor. The angle Ø is called the phase lag (or the phase lead if it is negative).

The product V₀*I₀ is called the VA of the load.

Notice that cos(Ø) is always less than one.

Greg

It's a conversion factor between current and power. For single-phase it's 1, for 3-phase it's 1.732.

Dear Vader,

Please reconsider your answer. A Power Factor can never be greater than 1.

Pure resistive loads have power factors of 1.0 which is called the "ideal" power factor. Reactive loads have power factors of less than 1.0, usually between 0.5 and 0.95

Power factor is a comparison of the power used by the load, called "real power," to the power supplied to the load, which is called "apparent power." The difference between the real power and the apparent power is called "reactive power." Reactive power performs no useful work but it must be supplied to customers in order for motors and other inductive loads to operate.

To calculate Power Factor in a single phase load.= Input Watts / (Load Volts x Amps x 1)

To calculate Power Factor in a three phase load.= Input Watts / (Load Volts x Amps x 1.732)

In a three phase circuit, the use of the constant 1.732 results from the fact that not all three phases are producing the same amount of power at the same time. Each phase's voltage and current move through zero at different times. Suffice it to say that the correct power from a three-phase system at any point in time is found by multiplying by the square root of 3. Using the square root of 1 as a constant in the single phase formula is optional.

sure you are not talking about power factor, right?

Dear, friend power factor is very simple:

is how efficient you use the electrical power that you consume.ie.

if you convert into active energy it's ok but if you convert into pasive energy ,you waist energy.

in other words , is not the same pushing a wall than open a door

pushing a wall you lost your energy and do not have anything, but if you open a door you can see the result of energy: to one action you have a reaction

you get it!!

I have recently learned to be more politically correct, so I won't say much . . .

Power Factor is the cosine of the angle between current and voltage, and that's all there is to it.

What P. F. tells you is another thing . . .

Call it the cosine of the phase angle between voltage and current (or the tangent of the loss angle for small loss angles).

The importance of power factor for the customer was mentioned in earlier posts but it is very important for system stability as well. Transmission and distribution lines are predominantly capacitive and loads are predominantly inductive. Reactive power represents unmetered power that must be supplied and sufficient reactive power is necessary to maintain system voltage and stability.

Insufficient reactive power was one of the contributing factors in the major blackout that affected large areas of the U.S. and Canada in 2003.

Let's keep it simple (KISS). Power Factor is the same as efficency in a combustion engine [miles per gallon]. The closer you can control your phase angle {voltage / current}to unity or 1, the more work you accomplish for the same kilowatt-hour.

Depends on whether or not you're the utility company! As a user, I'd like to get work out of VARS -- not WATTS!

The best answer on here is post 3 by K Rallapalli simple and yet true

____________________________________________

Thank you and good night

I'm not going to make a big deal out of this, but half of K Rallapalli's statement is true, "In other words power factor is watts/volt-amps in a AC circuit."

The first half of his statement, "Power factor is the ratio of real power and reactive power," is wrong. The reactive power is the sine of the angle between volts and amps. Perhaps he meant to say, "Power factor is the ratio of real power to complex power," or something along those lines.

E.L.I the I.C.E man.


simple as that. Hint (E leads I ) in an inductive load, I leads E in a capacitive load.

if the load is balanced then the power factor would be 1. But the best you can do is ~ 0.98, in essence for a general understanding 2% of the power is being lost.

for very large inductive loads, you simply run a synchronous motor on the main feed, you adjust the motor to keep the power factor at 0.98.

Now.

Hallo to all Engineers ,

Electrical Engineers asking to define power factor ? Thanks Still many participated well and contributed good piece of knowledge. But if you really must think how to improve it in your system that will be great job. Think and design a good automatic power factor correcting circuit , or build an APFC Panel for your substation and report your finding .Better let us have open a discussion on that.

Thank you all and good day.

My friend Abraham,

You have the opportunity to start a discussion about that topic.

Hi, Hot Question . I love it. If I am right, Look for Jule energy first, then convert to power. Ie 1/2 times (voltage times capacitance) squared= jules or .5(v*C)squared= jouels

example;

.5(500 volts * 1 mfd) squared = juels

Mr X

POWER FACTOR IS THE COSINE ANGLE BETWEEN CURRENT AND VOLTAGE IN THE CURRENT-VOLTAGE CURVE. THE MAXIMUM VALVE PF IS ONE.

Yes ! The shortest & simple definition !!!!!

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POWER FACTOR IS THE COSINE ANGLE BETWEEN CURRENT AND VOLTAGE IN THE CURRENT-VOLTAGE CURVE. THE MAXIMUM VALVE PF IS ONE.

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KVA x PF = KW

PF is always less than 1 as cosine's max limit is 1

Further to my Post #24

Factor in maths means "Multiplier"
So V x A is multiplied by PF to convert Reactive-Power[VA] to True-Power [W]