Watt-Hour Meter

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pablo r. reyes

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Is there someone familiar with power saving device available in the market, that is installed parallel to the loads, usually residential loads?

Could this device possibly reduce the power consumption? How does the device affect the rotation or speed of watt-meter disk?
 
Re: Watt-Hour Meter

It would be one of two-things. It's either a scam or it's illegal. If a homeowner wants to save on their energy bills, magical devices and contraptions aren't going to do it. Turning off ceiling fans when not in the room and changing incandescent lamps to compact fluorescents will.
 
Re: Watt-Hour Meter

We've seen this sort of thing come and go. They usually cost someone more money than they are worth. But this is not hard to imagine; they are worth nothing.

But just in case a new scam is hitting the market, can you give us some more information? Perhaps the name of the product, or their web site? We may have already seen, and evaluated the one you are talking about, and may be able to tell you more about it.
 
Re: Watt-Hour Meter

The ones I have heard of are usually in series with a resistive load, and distort the voltage and current sine waves. Utility meters are averaging and can't detect the actual power consumed accurately unless the power is a relatively pure sine wave. I am sure that there are others.

Jim T
 
Re: Watt-Hour Meter

What current the wattmeter reads? Is it the True Current on (resistive) or the Total Current (apparent)?

If it is the Apparent Current, I think the amount of current reads by the meter can be lessen by power factor correction (i.e. paralleling capacitor to the loads).

In this condition, the True Current delivered to the load is the same, but the Apparent Current cab be less.

by the formula:

Square of Apparent Current = Square of True Current + Square of Reactive Current

Here, reducing the reactive current will reduce the apparent current, but the true current for the loads is the same. Now, considering the input to coil of the meter is the Apparent Current, then it is possible to reduce the speed of watt-meter disk by reducing reactive current.
 
Re: Watt-Hour Meter

The Watt-Hour meter registers the energy used; that is,

W = integral(V*I*PF)dt (over the billing period)

If you increase PF, I decreases, and W remains the same. You get what you pay for.

Now correcting PF at the load will lower the copper losses between the meter and the load and also in the Poco wiring.

If you have a commercial rate, the PF penalty will be reduced as well.
 
Re: Watt-Hour Meter

pablo
A watt-hour meter measures watts, not va. The coils in a watt-hour meter shift the measured voltage and current by nearly 90 degrees. This pretty much negates any phase shift caused by the pf.

Jim T.
 
Re: Watt-Hour Meter

Originally posted by jtester:
pablo
A watt-hour meter measures watts, not va. The coils in a watt-hour meter shift the measured voltage and current by nearly 90 degrees. This pretty much negates any phase shift caused by the pf.

Jim T.
Click to expand...
Jim, the watt-hour meter measures watt-hours which are units of energy. Watts are units of power. Not quite the same.
 
Re: Watt-Hour Meter

rattus
I stand corrected. That is the result of posting before my second cup of coffee.
The idea about the coils and the phase shift is still the same. The watt part of the meter is the torque developed by the voltage and current on the disk. The hour part is the number of revolutions of the disk.

Thanks for the correction.
Jim T
 
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