power save devices

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jim dungar said:
Years ago when the local POCOs were having a shortage on generation they offered rebates to industrial for installing PFCC's. Never once did they encourage homeowners to add capacitors.

Now the local POCOs do not even penalize industrial accounts for 'bad' PF. So, in this area the only energizing saving reason to install capacitors is to reduce a demand charge.
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Jim:

Isn't there a benefit to the industrial uses if the use pf in a large facility with poor pf? Improving efficiency of the system?

In the case I noted would point of use be more beneficial?

Assuming all those VFDs most places utilize these days do not have an interaction issue?
 
brian john said:
Jim:

Isn't there a benefit to the industrial uses if the use pf in a large facility with poor pf? Improving efficiency of the system?

In the case I noted would point of use be more beneficial?

Assuming all those VFDs most places utilize these days do not have an interaction issue?
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Improving what efficiency?

Better PF means better usage of your transformers and conductors, what if they are only loaded to 60% right now, what will you do with even more extra capacity?

Often at the main service or unit substations, the harmonics caused by individual loads are 'self-mitigated' by the impedance of the power systems and the mutual cancellation with other loads. This is why the IEEE-519 standards talk about harmonics 'at the point of common coupling' not at the line terminals of a single device.

Three of the PQ studies I have done in the past year or so, resulted in me telling the customers the power system would not react well to fixed capacitors banks, and there was no reasonable payback for installing automatic ones.
 
paul renshaw said:
In some cases can't the improper use of caps in an industrial installation cause unwanted resonance within the system?
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It is possible. Power factor correction is a design problem. You don't just say, "Hey look, there's some blank wall space. Let's put a capacitor bank there. Just think of the money we'll save." If you don't get the right mix of reactive devices, and the right control scheme, you place the plant at some risk.
 
Regardless what some people think, harmonics and low power factor are not bad things of and by themselves. They are only bad when they negatively impact some thing else.

The meters read .45 PF - wow we better do something. Hmm, this happens only on weekends when the load is 60A on a 1200A service, is it a problem?

The meter reads 65% total harmonic current distortion - quick check for melting neutrals. Hmm, it is a 3PH 3W (no neutral) load and the total voltage distortion is only 4%.
 
jim dungar said:
Regardless what some people think, harmonics and low power factor are not bad things of and by themselves. They are only bad when they negatively impact some thing else.

The meters read .45 PF - wow we better do something. Hmm, this happens only on weekends when the load is 60A on a 1200A service, is it a problem?

The meter reads 65% total harmonic current distortion - quick check for melting neutrals. Hmm, it is a 3PH 3W (no neutral) load and the total voltage distortion is only 4%.
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meters read 0.45 PF today but averages .86 PF per month? no problemo
ITHD at 65% near an electronic ballast? no problemo.
VTHD at 4% near a dimmer? no problemo

meters average 0.45 PF a month on a commercial facility ? pay the PF penalty, if it is in the utility contract
ITDD at 10% measured on the secondary side of the main transformer? uh oh
VTHD at 6% measured on the primary side of the main transformer? uh oh
 
charlie b said:

It is possible. Power factor correction is a design problem. You don't just say, "Hey look, there's some blank wall space. Let's put a capacitor bank there. Just think of the money we'll save." If you don't get the right mix of reactive devices, and the right control scheme, you place the plant at some risk.
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hear hear !!!
 
power save devices

There is a guy who lives near me that found out I'm an electrician. He tried to convince me this was the next new wave in home energy saving devices to sweep the nation, and I should jump in before it was to late. Well that was three years ago, and I didn't jump, at the time, after seing his demo unit, I told him he should be selling these things to the supply houses, they wouldn't be able to keep them in stock, If they are that good. Also Home Cheapo would have already started selling them. Bill
 
There was a guy in the Phila. area last year peddling these things. He found out I have a customer with a bunch of locations and tried to talk me into setting up a meeting with them- NOT!!! First of all he talked fast. Secondly he stuttered. I told him to get lost.
 
Well iam not a engineer , so iam guessing pf to me is a value of AC voltage to current out of phase in circuit . This is old time inductance or ac reactance how or what makes no difference to the circuit its there . They say a watt meter can not measure ac reactance because the watt meter uses volts and amps to measure wattage if its out of phase its not what the wattage would actually be ? So lets see bad pf you use less watts ? increase heat in circuit damage wiring insulation ? Or just measure less watts on meter so if you correct pf you use more current as voltage and current are maxed out and there now in phase with one another so how does it save you money by correcting pf ? I can understand harmonics and the issue of current increased by odd harmonics these induce current into the conductors and add in the same direction as the normal current flow in circuit which now is another heat and damaging factor and can effect insulation of wiring circuits and motor windings ect ect , so how do we stop harmonics and correct pf shut off power . and there is no magical way to save power IMO comments ? Best to yas
 
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paul renshaw said:
Has anyone installed or had any real world experience with these power save devices? From what I can see, they alter the power factor to bring it closer to unity. Is there really that much use for it in a normal residential situation? I have installed caps in industrial faciliteis that were penalized for bad power factor, and it really helped their monthly bills. Do the residential meters even keep track of total VA? I thought they were strictly KW meters. Their video shows the amp load decreasing when switched on, and it shows the power factor lowering, but you can not see what the total KW or KVA is or how it changes in the video.
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There is only one power saving device that works in a residential application.

It is called a switch.

:smile:
 
Power savars

Power savars

Well look at POWER FACTOR take the formula and do two or three different ones change the pf each time at same watts it does save maybe one amp or two . The real power savor is when one has a good percent of efficiency into that pf formula when you include E x Ef x Pf x 1.73 then it takes current down but pf by itself is not enough . To save energy or money its more then just a capacitor bank. Its the service from the get go the conductors , equipment, and a good planned electrical project not a cheap install but designed to be efficient in the best and least wasteful manner . just thinking a bit best to yas
 
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