Power factor conditioner

Anything electric, AC or DC

Postby Kevin A » Sun Dec 04, 2005 8:13 pm

PB,

What effect would this have on startup loads on the AC unit? Would it reduce the generator size requirements that have been debated here?
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Postby Sonetpro » Sun Dec 04, 2005 10:16 pm

From what I read this is just as it claims. It is a power conditioner. Or in other words a filter that reduces A/C ripple. The whole article only talks of inrush current. This is the same thing a rectifier does in its A/C caps before it goes to a PI filter.
I also see that the only tests done are with inrush current. But OHMS law holds that if you have x amount of resistance at X voltage you will always have X current.
This article never states that you need less current. Only filtering inrush's so to make the meter thinks its delivering a contant load.
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Postby GeorgeTelford » Mon Dec 05, 2005 4:39 am

Hi

If it saved up enough power to enable start up, yes no problem. (but according to their own graphs they charge when the power is switched on)

If its supposed to reduce the amount of power used by the motor (by any apreciable amount), snake oil comes to mind, its just not possible. The savings would be miniscule and the capacitors would be long dead before you recouped the costs.

A capacitor can smooth out the power, but there is no way that it can dramatically reduce the power consumed by a motor (smoothing the power can obviously cause a small gain and I do mean tiny)

Power factor (the power "that seems" to be required but not actually used) is always a strange one to explain Its the amount of power thats needed to be available for a motor to work, but its not the actual amount power consumed.

Reactive loads such as inductors (motors) and capacitors dissipate zero power, yet they drop the voltage and draw current giving the deceptive impression that they actually do dissipate that amount of power.

This "phantom power" is called reactive power, and it is measured in a unit called Volt-Amps-Reactive (VAR), rather than ACTUAL watts.

Reactive power is symbolised with the letter Q (look at the chart mentioned in the original link) the only column with any obvious difference is the Q column or VAR, Then you have apparent power Symbolised by the letter S this is volts and amps without regard for the Phase angle, but even this isnt the TRUE power, true power is a combination of the two, or a measurement of volts and amps accurate, you do not get billed on VAR, only on the P or watts (true power) column is your billing amount note the difference there....

So although the power company give you 110 Watts because you only borrow the last 10 and give it back you only get billed for 100 Watts.
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Postby madjack » Mon Dec 05, 2005 4:47 am

...it makes sense to me...the power conditioners are capacitors and as such they act on the line voltage just like the starting capacitors on a motor...the sit there until needed and then supply the "extra" voltage need whenever a motor starts running...gee I agree with and understand George for once.
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Postby Sonetpro » Mon Dec 05, 2005 7:41 am

Yes you can change the VAR with a cap. But you cannot change true watts
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Postby vairman » Mon Dec 05, 2005 9:31 am

I have used a unit that converts the normal AC sine wave to an AC square wave, then what this unit does it monitors the motor load verses rpm and then it reduced the height of the square wave to meet the motors power needs... This works well, but on some appliances like electric dryers and dishwashers that have heating elements it doesn’t work, and new refrigerators the compressors are matched so close that there is no gain, and furnace blowers and A/C condenser fans also have no gain in performance.. But the unit works well on the A/C compressor and on other things like washing machines and air compressors...
Also 1 more note a motor running and not conneteced to a load will pull almost full load amps and if you add some load to the motor the amps will drop.. ( we were doing amp draws on motors and found this out)

If I can remember th name of tho company I'll post the information..

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Postby GeorgeTelford » Mon Dec 05, 2005 9:53 am

Hi Greg

Free running motors use the lowest Amperage, Stall current is the absolute highest that the motor will draw and as you add more load (from free running) the amperage goes up with load.

The angle between P and S is the Impedance Phase angle, if you can remember basic Trig, you can work out a missing side from any two givens
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Postby vairman » Mon Dec 05, 2005 11:25 am

GeorgeTelford wrote:Hi Greg

Free running motors use the lowest Amperage, Stall current is the absolute highest that the motor will draw and as you add more load (from free running) the amperage goes up with load.

The angle between P and S is the Impedance Phase angle, if you can remember basic Trig, you can work out a missing side from any two givens


I know that how it's supposed to be but in our tests 1ph. motors running at no load pulled more amps than the same motor running at light load, the motor tested was a 120v. 1hp, 1-ph 1725rpm 16FLA. on the bench it was pulling 15amps under no load, then under light load (friction bar agaist the pully) the amps dropped to 13.5amps... We repeated the same test with 3 diffrent motors and got the same results. Go figure huh? if you get a chance and have an amp-meter try it..

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Postby vairman » Mon Dec 05, 2005 12:37 pm

I found the web site for the controllers...

http://www.eslainc.com



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Postby GeorgeTelford » Mon Dec 05, 2005 12:55 pm

Hi Greg

Looks like we have wires crossed here, I always think of full Amps as the Max ie the Stall Amperage (which could literally be hundreds of amps), where you mean the normal running amps, so yes to what you mean and no its not anywhere near the stall Amps. BTW the anomally is probably down to the motor over revving because of the lack of load

We are both right, because we are talking totally different meanings to full Amps...
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Postby GeorgeTelford » Mon Dec 05, 2005 1:10 pm

Hi Greg

That ones a chopper circuit, basically a dimmer circuit for motors, what I will say is that this will work to a certain extent, BUT when the compressor needs 20 Amps to run, it will take 50Amps chopping at this point will only degrade performance....

Go back to the power factor stuff above, if less is supplied motor will not run ie if the true wattage supplied is maximised (by that device) at lower than the required VAR then the motor will not run.........
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Postby vairman » Mon Dec 05, 2005 1:13 pm

GeorgeTelford wrote:Hi Greg

Looks like we have wires crossed here, I always think of full Amps as the Max ie the Stall Amperage (which could literally be hundreds of amps), where you mean the normal running amps, so yes to what you mean and no its not anywhere near the stall Amps. BTW the anomally is probably down to the motor over revving because of the lack of load

We are both right, because we are talking totally different meanings to full Amps...


Oh yea, I did mean nameplate full load amps, not Locked rotor Amps..

Greg :)
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Postby GeorgeTelford » Mon Dec 05, 2005 9:09 pm

Hi Powder

By the looks of their graph it drops the VAR by 1350 so The power factor wouldnt be a "factor" in deciding genny size any more (now its the normal running wattage that counts) However the Inrush current only dropped by 2 Amps on their graphs so you still need to size to allow for start up current.

The way past all this would be.....

Get a large invertor capable of running AC

Add two Batteries

Add Large international charger 50 A

Which can be run by a small 900 to 1000 watt genny

The batteries take up the slack, the AC would not be run continuously, ie the cycling would give the batteries some recharge only time, between cycles.

Doesnt save much if any money (genny far cheaper but add invertor and extra battery), but it does save fuel (bigger genny is wasting fuel when not covering Start up and PF surge) Genny is lighter, but add back weight of one extra battery and invertor too. Genny would be quieter.
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Postby bdosborn » Wed Dec 07, 2005 1:17 am

Powderburn,

Back to your original post, the PF correcting unit is a rip off.

1. They picked an especially inefficient motor to sell the their unit.
2. Capacitive correction of PF has to be tuned to the load. Otherwise you get especially nasty power quality problems (resonance) ie. Your washer works great but your computer burned up.
3. George is right, you pay for Kw-Hrs, not amps-hrs. No payback. Ever.

Pure snake oil.

The AC starting:

Single phase induction motors tend to stop with the rotor and stator poles aligned. That means no starting torque. By using a capacitor to phase shift the line voltage, you add another leg so you have more starting torque. But, AC units have the motor connected to a compressor so they're just hard to start. There's no substitute for cubic inches.
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Postby Larwyn » Wed Dec 07, 2005 3:44 pm

VAR (power factor) is being closely metered in the power industry. In part to help calculate the need for capacitor banks or reactors (induction units) for power factor correction. If you are in the power generating/transmission business VARs are losses and a lot of money is thrown in their direction to minimize them.

Watts + Volts * Amps * Cos(angle)

Vars = Vots * Amps * Sin(angle)

The angle in the formula is the difference in angle between the potential and the current on the same phase.

So the actual purpose of power factor correction by the utilities is to be able to bill and meter every amp possible, and those amps that go to VARs do not show up on the watt hour meter at your house.

I can see no advantage to correcting power factor on the load side of a meter. I'm no engineer, but I do work with metering high voltage lines in the power industry.

As a side note, I would not be surprised if some day in the future we may actually be billed for VARs as well as Harmonics. If you think Vars are complicated don't even get me started on harmonics.
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