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From what I know so far (might be wrong), The ideal or unity power factor means that all the energy is consumed by resistive components and are converted to heat, light, etc. In this case apparent power and real power are equal.

On the other hand, if reactive power exist in the system we have stored energy that is not used. That is why power factor correction is used to get rid of the reactive power (stored power that just sit there and do nothing).The power factor correction introduces other storage unit so that they would provide current back and forth between the storage elements and hence less current is drawn from the power supply.

My question is if this statement that I conclude from the correction of the power factor is correct: "By correcting the power factor less energy is used in the circuit and hence less current is entering the circuit.This would result in less power loss since current has decreased"

If this statement is not true, then what is the point of power correction?

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  • \$\begingroup\$ My power company bills me actual used power, not apparent power. \$\endgroup\$ – PlasmaHH Feb 12 '16 at 16:05
  • \$\begingroup\$ @PlasmaHH But if you do power factor correction, you would have less real power because the current has decreased. Therefore, you end up paying less. \$\endgroup\$ – Jack Feb 12 '16 at 16:08
  • \$\begingroup\$ The real power will always be the same, and due to the added losses, it will even be a bit more. Apparent power will be less, but who cares about it when you are not billed for it. \$\endgroup\$ – PlasmaHH Feb 12 '16 at 16:14
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    \$\begingroup\$ Possible duplicate of How power meter works for residential buildings? \$\endgroup\$ – uint128_t Feb 12 '16 at 16:18
  • \$\begingroup\$ @uint128_t It is not a duplication. I am talking about power correction and improving loss. \$\endgroup\$ – Jack Feb 12 '16 at 16:19
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By correcting the power factor less energy is used in the circuit and hence less current is entering the circuit.This would result in lower electricity bill and less power lost since current has decreased

No. Assuming a fixed voltage (very low impedance) supply, like the power grid, low power factor causes more current than drawing the same power at unity power factor. However, you get billed for the real power consumed, not the "reactive" power.

Power companies don't like low power factors because the higher current for delivering the same power causes waste and stresses on their system, and reduces their capacity to deliver real power.

A typical small scale user, like a house, isn't going to save money by presenting a better power factor. Again, you get billed for real power used. Large industrial customers get billed for real power, but there are penalties added for low power factor. The power factor is monitored, and they get charged extra based on the worst power factor during the month, averaged over a minute or hour or something. Again, this does not apply to ordinary residential customers.

reactive power exist in the system we have stored energy that is not used

Not the way it seems you are thinking of it. At low power factor, you draw more energy than you use during part of the power cycle, then give it back during another part. The total energy drawn per cycle is still the same as with unity power factor, but a lot more energy gets sloshed back and forth. The sloshed energy averages to zero, so doesn't cost you anything, but all that sloshing causes inefficiencies and other problems for the power company.

if you do power factor correction, you would have less real power because the current has decreased. Therefore, you end up paying less

No. Power factor correction doesn't cause you to draw less real power. It minimizes the power you cause to slosh back and forth that you end up not using, but you still use the same power in the ideal case.

A little bit of the extra sloshing power will be lost in the wires on your side of the electric meter, so you get billed a tiny amount less. However, some schemes for doing power factor correction take a little power themselves to run, which costs you a little more. That's generally quite small too though.

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  • \$\begingroup\$ A note: My power utility contract has some pages about required powerfactors; but obviously nobody reads those or has even an idea about what those are, which makes me wonder if anywhere the companies actually measured it and/or enforced it... \$\endgroup\$ – PlasmaHH Feb 12 '16 at 16:16
  • \$\begingroup\$ @Plas: Power companies do monitor the power factor of large industrial customers, and charge them more for low power factor. I don't know of any place where this is done for individual house. It's certainly not done for houses here in my town in Massachusetts. \$\endgroup\$ – Olin Lathrop Feb 12 '16 at 16:23
  • \$\begingroup\$ @OlinLathrop so power correction would decrease the power loss in wires between the reactive components? for example the power that is consumed by internal resistivity of a non-ideal transformer? \$\endgroup\$ – Jack Feb 12 '16 at 16:29
  • \$\begingroup\$ @OlinLathrop and if so , wouldn't it result in drawing less current from the generator. \$\endgroup\$ – Jack Feb 12 '16 at 16:32
  • \$\begingroup\$ This part of your answer"No. Assuming a fixed voltage (very low impedance) supply, like the power grid, low power factor causes more current than drawing the same power at unity power factor. However, you get billed for the real power consumed, not the "reactive" power.", so if we are drawing more current doesn't it mean that the average power increases? \$\endgroup\$ – Jack Feb 12 '16 at 17:00
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For me correcting/improving power factor is very similar to the counter weight we find in elevators.

Just imagine how difficult it is for the elevator motor to handle the carriage weight without the counter weight.

Now power company is the elevator motor, the carriage is your load and correcting power factor is the counter weight.

Cheers...!!

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Your assumption is not correct.

The power meter accumulates the total amount of real power that is consumed.

The problem with reactive power is that the power utility has to deliver that power in addition to the real power that the customer is using. That means that the current required by the customer is larger than is being charged for.

The power utility has to make the all of current-carrying components larger to handle the (approximate) sum of both real and reactive power.

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If you have some terminals rated for providing a particular power/current, that rating will be for apparent power. While you will only be billed for real power, your fuses blow and your cables ignite for the amount of apparent power being run through them. So if your big conference with its hosts of power supplies on the stands is threatening to exhaust your terminal limits, you might squeeze out a bit more by mounting a suitably large synchrone motor with a reasonable flywheel and adjust its excitation such that the flywheel will cater for the power factor.

Of course, this scheme is complicated by all those power supplies not drawing a proper sinoidal current with straightforward power factor. So the excitation will only be a compromise for correcting the power factor at the fundamental frequency of the current.

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