• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Alternative to AE - P.F. Correction

ignisuti

New Member
How will you measure your washing machines current PF?
I think that takes us slightly off topic and may better be discussed in a different thread. Before we diverge down that path, I want to get to the root of something first. Can we agree on this statement: A poor power factor results in more cost to the home owner for running the same appliances than if a better power factor were in place.
 

smanches

New Member
There is NO Power Factor or Reactive Power charge on my electric bill. I'm charged for Real Power like all of you. However, if you have a washing machine with a poor power factor, you end up using more Real Power to run one cycle than you would if you use the correct amount of capacitance to improve the power factor. I don't think this is disputable. I believe it is a fact and there are many websites that confirm this.
And I'm asking why does it make you use more real power? The link you posted does not discuss power facter affecting real power at all.

The only supposition I can think of is if you are near the limits of your power lines. The extra apparent power would increase the power dissipation from those lines, hence losing efficiency. But that would be only when your pussing enough current (apparent and real) to start heating up the lines.
 

smanches

New Member
I think that takes us slightly off topic and may better be discussed in a different thread. Before we diverge down that path, I want to get to the root of something first. Can we agree on this statement: A poor power factor results in more cost to the home owner for running the same appliances than if a better power factor were in place.
Umm. Can't agree with that, sorry.

Apparent power cannot be used by an appliance. The effect it causes is on the distribution lines and transformers of the system, due to additional current harmonics that put additional stress on the distribution lines. This power cannot be harnessed though.
 

ignisuti

New Member
The link you posted does not discuss power facter affecting real power at all.
Please review the link again: POWER FACTOR CORRECTION

These sections were copied & pasted directly from that link

What does it do to my electricity bill?
In a 3 phase supply, kW consumed is (VOLTS x AMPS x 1.73 x Power Factor) / 1000. The Electricity Company supply you VOLTS x AMPS and they have to supply extra to make up for the loss caused by poor Power Factor

Why do I need Power factor correction?
Capacitive Power Factor correction (PFC) is applied to electric circuits as a means of minimising the inductive component of the current and thereby reducing the losses in the supply.
The introduction of Power Factor Correction capacitors is a widely recognised method of reducing an electrical load, thus minimising wasted energy and hence improving the efficiency of a plant and reducing the electricity bill.
 
Last edited:

smanches

New Member
"Check your electricity bill to see what your power factor is! "

There is one HUGE assumption made by that page. It is moot for homes since you aren't charged for poor power factor.
 

audioguru

Well-Known Member
Most Helpful Member
A motor is designed to run without power factor correction. It draws a certain amount of real current. If it has its power factor corrected with a capacitor then it does not draw less real current. Instead the utility supplies less or none apparent current. But your home is billed for Real Power, not apparent power.

In Google I asked, "Does Power Factor Correction Reduce The Electricity Bill?" All answers said no at home but said maybe if you have a factory.
 

Mike_2545

Super Moderator
Interesting thread, The place I work put in a Capacitor bank (PF correction device), as we run 3 fans 4 pumps continually with other inductive loads kicking in and out through out the day. I saw an immediate decrease in the electric bill, 10%-20% the average bill was $1100.00 now I see the average at $900.00.
Most of this is resistive loads but a fair amount is inductive. As far as I know we have a residential meter, so I would have to say in our case it has saved a lot of cash in the first year.
 
Last edited:

Nigel Goodwin

Super Moderator
Most Helpful Member
Can we agree on this statement: A poor power factor results in more cost to the home owner for running the same appliances than if a better power factor were in place.
Everyone, with the exception of yourself, disagrees entirely.

The quote you gave

The introduction of Power Factor Correction capacitors is a widely recognised method of reducing an electrical load, thus minimising wasted energy and hence improving the efficiency of a plant and reducing the electricity bill.
clearly refers to industrial use, hence the use of 'plant' - where the electricty company monitor the PF and charge accordingly. This doesn't apply to domestic useage.
 

mneary

New Member
"Real" current is is a very specific term in electrical engineering, that is that which is in phase with the voltage.

The residential customer is charged only for that portion of the current he draws which is in phase with the voltage.

There is a specific engineering term for the current which is not in phase with the voltage. This current is called "imaginary". Although this current exists and can be measured, the residential customer is not charged for it. "Imaginary" or reactive current does no work, and except for inevitable losses, is returned (reflected) to the power company.

Your ammeter is not aware of phase, so taking a voltage reading and then a current reading gives VA, which is the total of Real and Imaginary power.

A motor will draw power to do work, plus some inductive (imaginary) current which it returns to the power company later. In the simplest case of a pf correcting capacitor, the cap draws imaginary current with the opposite phase from the motor. The goal is that the net outcome is the power company doesn't have any "imaginary" current flowing in and out of the customer premises and therefore is only providing "real" (in phase) current.

You knew all this. Where am I going?

The industrial customer is billed for the real power (work) plus the out of phase (imaginary) current. He often has large inductive loads, and has an incentive to return the power factor to 1 so as to not waste the power company's distribution resources.

The residential customer has a sophisticated meter, but the choice was made for it to monitor only real power (work) and to the best of our knowledge the meters all ignore out of phase (imaginary) current.

A consumer device, however well intentioned, which corrects power factor in the residential environment, can not and does not save any meter clicks.
 
Last edited:

ignisuti

New Member
Thanks everyone for putting up with my questions thus far and for continuing to post information.

Just to beat this topic to death, let me try this one last time...
If I leave 5 ceiling fans running for a whole month in my home, all of you are saying that the I'll end up paying the exact amount whether or not I have power factor correction?

The part I'm hanging up on still is that I've been taught that a poor power factor will make an inductive load (like a fan) work harder. Meaning that to run at the same speed, the fan needs to use more Real Power than it would if it had a better power factor. The reason I'm beating this into the ground is because the YouTube videos I've seen for common power factor correction devices show you this concept very clearly with a DMM attached. What they show aligns perfectly with what I've been taught and I can't see any smoke or mirrors in the videos. It all looks legit.

Mike2545, if there is any easy way for you to determine if you have a residential meter, then I would be really interested in knowing. Please take a look at your previous and current bills to see if there is any mention of power factor charge. I'd appreciate your feedback as well.
 

mneary

New Member
TThe reason I'm beating this into the ground is because the YouTube videos I've seen for common power factor correction devices show you this concept very clearly with a DMM attached. What they show aligns perfectly with what I've been taught and I can't see any smoke or mirrors in the videos. It all looks legit.
An external gadget cannot alter the relationship between I with respect to V internal to a two-terminal device such as a fan. It can alter the outside appearance of I with respect to V, by adding reactive current to balance that drawn by the fan. (This outside appearance of I wrt V is power factor.)

You can plug certain old motors into a motor controller to reduce the input voltage when it detects that the motor is lightly loaded. It only works with motors which are oversized for their task. Each old motor needs an individual controller because the load must be detected separately.

[edit] A short demo like the one on YouTube can easily be arranged using a Variac. [edit]

Once started, an oversized motor will run well on reduced voltage provided its conditions are carefully monitored. A sophisticated motor controller can and does save power by monitoring the work being done and applying the correct voltage. But the motor alone has the final say about the relationship of I with respect to V at its terminals.

They sold devices for a while called "Green Plug" and I was suckered into buying one. Problem was, my fridge wasn't old enough. The Green Plug cheerfully reduced the voltage and my poor fridge hummed and buzzed and clicked and quit. Saved a lot of energy. :(
 
Last edited:

ignisuti

New Member
mneary, you've posted helpful & constructive information that appears credible as opposed to blind accusational nonsense. Thank you for that. I've given you some reputation points. ;)
 

bgudgel

New Member
ignisuti said:

Quote:
Originally Posted by audioguru View Post
Your home meter does not read apparent current.
Technically correct, but I must state again that a poor power factor makes you use more Real Power to run the same load of laundry. The Real Power is read by your home meter. Therefore, you end up paying more on your electric bill because of the poor power factor.


OK, so then, install larger diameter wire in your home so you have lower I^2 losses.
boB
 

EE World Online Articles

Loading

 
Top