Is power factor correction legal to do in your own home?

[W1RKW]

http://www.power-savetv.com/3400.html

[W4EWH]

http://www.power-savetv.com/3400.html

Yes, power factor correction is legal, and it's routine on large industrial motors. However, the prices mentioned on the website are extraordinarily high for what amounts to a capacitor.

W1AC

[K3ZS]

Looks like this is for 3 phase, will something like it work with single phase?

[Opcom]

I have some typical waveforms from when I suspected a generator problem in my commo truck. These may be interesting.
1.) 12000BTU air conditioner's condensing unit current waveform does not lag too badly due to capacitor run motors. 11 Amps.
2.) Current waveform of evaporator blower induction motor lags because no capacitor is used with this kind of motor. 2 Amps
3.) 9 inch color TV current waveform shows transformerless bridge rectifier with capacitor input filter. 0.7 Amp

[WZ1M]

The amount of money saved for single phase is not worth the trouble and expense for a household. Hey, add a bunch of caps and get that power factor to a leading of about 115 and see who shows up on your doorstep.
Regards,
Gary

[k4kyv]

The amount of money saved for single phase is not worth the trouble and expense for a household. Hey, add a bunch of caps and get that power factor to a leading of about 115 and see who shows up on your doorstep.

Who?

And why would adding caps to cause the current to lead be any more of a problem than using motors and other inductive devices that cause the current to lag?  Power factor of 0.5 is 0.5 regardless of whether it is leading or lagging.

The best efficiency would require the power factor to be exactly 1.0, that is, no lag nor lead.  The voltage and current would be exactly in phase.  But wouldn't that require some means to constantly vary the capacitance according to the amount of inductance in the load?

They don't explain how the Power-Save works, but maybe that's what it does.  A bank of capacitors, a power factor sensor, and a control unit that electronically or mechanically  switches in the number of capacitors that brings the power factor closest to unity.

[WZ1M]

Utilitys around here dont want a leading power factor, hurts there profits.

[KA1ZGC]

[Utilities] around here [don't] want a leading power factor, hurts [their] profits.

That makes no sense. How could a leading power factor change the number of billable kilowatt-hours you draw from a utility? Energy can be niether created nor destroyed.

[Ott]

[Utilities] around here [don't] want a leading power factor, hurts [their] profits.

That makes no sense. How could a leading power factor change the number of billable kilowatt-hours you draw from a utility? Energy can be niether created nor destroyed.

The problem is "VAR"... a decent explanation here...

http://en.wikipedia.org/wiki/Volt-amperes_reactive

a better one here...

http://www.sandc.com/webzine/2002/041502_1.asp

Large machine shops correct for var to save on utility bills...

http://www.thomasnet.com/products/capacitors-power-factor-correction-pfc-10481208-1.html

An informal discussion of cfl induced var here...

http://www.leonardo-energy.org/drupal/node/2407

[WZ1M]

Years ago, and I mean years, it was explained to me that if you have a laging power factor the utility has to come up with the extra to maintain a certain voltage on there distribution line. My power company will accept no less than .65 lag. Below that is putting more load on there equipment. A leading power factor, as explained to me was, for them to not to produce as much as needed to maintain the line. For instance, we had a 5000 HP chipper that was constantly going from no load to full load. Power company had a voltage drop on there 4160 line when the chipper was under full load. This affected the rural area around this community. By adding a bank of capacitors on each leag of the three phase line, at the motor, this helped to keep the power factor up to an acceptable figure.

[Tom WA3KLR]

Residential power meters are true power meters; you are not billed on apparent power.
All other power meters should be true power meters also.

[k4kyv]

An informal discussion of cfl induced var here...

http://www.leonardo-energy.org/drupal/node/2407

Then I lit a 25 watt CFL. It measured 25 watts and 52 volt-amperes out of the inverter, which indicated a power factor of about 0.5.

Incandescent lamps present a load whose power factor is very close to 1.0. But a 25 watt CFL puts out as much or more light than a 100 watt incandescent, so it would appear that the line capacity would still be stressed less if all existing incandescents were replaced with CFL's.  But if widespread, mandated conversion to CFL's allows the power company to delay upgrading their infrastructure as more and more customers are added to the grid, power factor may eventually become a significant problem with electric power distribution.

[Rob K2CU]

You all know what would happen in CFL's were installed widespread. Say the result was a 10% savingsd in your electric bill. Then the utility company would cry to the PUC that they were in trouble because revenues were down and therefore taxes were down also. Then watch the rates go up 15% without question!

[Jim KF2SY]

PF correction is common in industrial/commercial motors.
In residentail situation, your modern appliances have the caps for PF.
My dishwasher motor I recently replaced had a big cap hanging near the motor for PFC.
Probably no significant cost advantage for a residentail setting.

[flintstone mop]

It's discouraging to know that whatever we try to do save a buck, that most of the time it's a waste of time.
It seems that wiring a transmitter for single phase 220vac compared to 115 vac is only effecient route to take.
Going to three phase only saves pennies (for the big boxes...50kw)and now power factors are fruitless.
Oh well

Fred

[Steve - WB3HUZ]

It's also fairly common on many modern switching power supplies, so PF correction is already happening in most homes.

PF correction is common in industrial/commercial motors.
In residentail situation, your modern appliances have the caps for PF.
My dishwasher motor I recently replaced had a big cap hanging near the motor for PFC.
Probably no significant cost advantage for a residentail setting.

[flintstone mop]

It seems that a wizard invention that helps us save money on utility bills (I know CFL's are poison...L.E.D. prices outta sight) (OR heating with wood stoves) then the DAM utility sees the usage go down so THEY up the rates to overcome the lost income. Same with Gasoline....a few more vehicles getting above 20MPG on the road now, compared to 5 yrs ago. We're in a vicious circle here.

Fred

[k4kyv]

The capacitors in small appliance motors are not necessarily there just for PF correction.  While shaded pole motors require no capacitor, they are low in efficiency and present an inductive load.  PSC (permanent split capacitor) motors run at higher efficiency and high power factor at rated load.  The name comes from the fact that the starter winding and capacitor are permanently wired into the circuit, with no switching mechanism to disconnect the capacitor after the motor has started.

For a simple basic discussion of single-phase induction motors, check out

http://www.iprocessmart.com/leeson/leeson_singlephase_article.htm

[WA1GFZ]

PF correction is quite common in Aircraft systems. Unitrode now TI sell a number of different controllers. I would think the power company would love all equipment to have a PF of 1. I think in some EU countries you need PFC in anything running over 750 watts if I remember.
All it takes is an average current mode converter running nice and fast.

[WA2TTP Steve]

Power Factor from the Utility point of view.

I spent 30 years in power system operations and power factor compensation is  finely tuned to match the load characteristics as they vary hour by hour during the day. The goal is to correct the PF as close to the load as is practical. This is done to reduce system losses. If all the reactive needs had to come from the generator then all those amps would consume valuable capacity on the transmission system that could be moving real power. I’ll give an example of what occurs during morning  load pickup that tends to drive the PF into the lag due to motor and other reactive loads. The key indicators used by System Operations to know when compensation is needed is usually the decline of transmission voltage and buildup of lagging Mvars on the generators.

The distribution circuit is the first point of correction using a combination of fixed, timed and remote controlled field caps. Fixed are on the circuit at all times. Timed are on clock control the say might come on at 8 am and off at 9pm Monday to Friday. Remote controlled  caps are turned on as need by  System Operators from the control center via radio control. These are generally brought on in groups by a common code.

After the distribution caps are on. Then transmission caps would be placed in service via remote control one at time at the substation the needs them. These caps operate at 69 to 345 kv as a rule and are made up of many series and parallel caps to make on large cap bank. There are also static var compensators , SVC’s, on some systems that are adjustable over a fairly wide range to fine tune the reactive output needed. In New York the SVC’s  are used  to enhance  transient stability following system faults than  steady state voltage control.

After all the field caps and  transmission caps are in service then its up to the generators to supply the reactive demand. This is done by increasing the field current which raises the terminal voltage and therefore supports the transmission  voltage. Many utilities do not have enough caps to meet all the reactive requirements on very high load days which is why the generators have to supply  it. If the reactive demand gets high enough  then the generator may have reduce it’s MW output to be able to supply reactive without over heating.

This was just simple overview of what goes on to maintain a good PF. Aside from the customer load the power system itself needs to be compensated. Transmission lines loaded above there surge Z  level, about 70%, need transmission caps to maintain system voltage. Also transformers and DC to DC converters that used on some of system ties lines are reactive hogs.

Also utilities don’t like leading power factors either. They don’t make $$. Instead they cause the system voltage to go high which can lead to equipment failures if not controlled. The generators field current will be very low to allow them to absorb  leading reactive. This weak field can lead to generator instability if a fault occurs on the system. This out of step condition can cause the unit to trip or be damaged.

Steve,
WA2TTP

[k4kyv]

It seems that a wizard invention that helps us save money on utility bills (I know CFL's are poison...L.E.D. prices outta sight) (OR heating with wood stoves) then the DAM utility sees the usage go down so THEY up the rates to overcome the lost income. Same with Gasoline....a few more vehicles getting above 20MPG on the road now, compared to 5 yrs ago. We're in a vicious circle here.

If usage goes up, prices go up.  Supply and demand, they say.

If usage goes down, prices go up.  They have to compensate for lost revenue.

If usage stays the same, prices go up.  They have to make up for "Inflation".

But damn.  Salaries, wages and pensions  don't go up.

[WZ1M]

Don, isn't that the american way?

[WA1GFZ]

it is learned from the oil company execs. Poor guys need to make a profit you know or they will be looking for corp. welfare down at the beltway..

[Steve - WB3HUZ]

You make a profit. Are you an oil company exec?

it is learned from the oil company execs. Poor guys need to make a profit you know or they will be looking for corp. welfare down at the beltway..