Nowadays, it’s easy to measure watts to home appliances with Kill-A-Watt meters. However, living in Mexico, ordering one across the border would be cost prohibitive as shipping charges would be higher than the cost of the meter itself, and that's without taking into account import taxes!

Knowing that inexpensive Kill-A-Watt meters measure power on 120V circuits, a way will be shown to calculate power on any single phase motor load at any voltage. This same technique can be used on three phase motors as well except that you’ll have to adapt the formulas for three phase power calculation. For sake of simplicity, we’ll measure power on a 120V, 5000 BTU/h, thru-the-wall air conditioner.

Step 1: Alternating Current Motors

Power on Alternating Current motors

Most people versed in alternating current electricity know that in order to measure power on electric motors, Amps and Volts readings would not be enough. There is another parameter – known as power factor- which affects the calculation of power in Alternating Current loads.

                       Power = (Volts)(Amps)(Power Factor)         [Watts]                                        (1)


Power Factor is the ratio of real power (measured in Watts) to apparent power (measured in Volts-Amperes or VA). Power Factor is a quantity that cannot be higher than unity.


                                 Power Factor = -----------------                                                            (2)


In motors, real power is the one that does the actual work, the apparent power (VA) is made up of real power and reactive power. Reactive power produces the magnetic field that makes the shaft rotate. Unfortunately, an Amp meter measures total current in Amps which –in case of alternating current motors- is comprised of real current and reactive current, therefore, they are not easy to separate in order to calculate running Watts.

I don't get the joke, just doesn't make any sense, but at least your procedure is good
If you refer to the name of the instructable as the joke, it's a play on words which obviously backfired. <br><br>Speaking of names, is there any reference between yours and the mayan feathered serpent deity? <br><br>Have a great day!
I just realize myself how rough I must've sound in my comment I apologize for that was having a bad moment at work...Very smart ! Yes , kukulcangod is the god of knowledge , I was born during the equinox same time the pyramyd of kukulcan produces the shadow of the feathered deepens descending again from the skies<br> My friend, wireless electricity was their specialty as well , in fact a form of it now called bio energy, or zero point energy, or gone etc. Modestly but like them I have been able to extract energy from the ground, orienting my electrodes north south and with a special circuit...Great instruct able continue on Thanks.
<p>Happy birthday kukulcangod ! </p><p>I thought of you today, I just saw a video on youtube about the feathered serpent going down the pyramid.</p>
Hey Kukulcangod, no problem, that's OK, we're only human. <br> <br>What kind of loads have you been able to feed with the energy you extract from the ground?
Very detailed! Nicely done!<br>I see you have a meter, how accurate is this procedure?
Capacitors tend to draw harmonic currents which should affect the power triangle relationship. As to how accurate this is, well, I would say that +/- 10% accuracy compared to a power meter.<br><br>In spite of this wide difference, this method beats having to guess power when there is no power meter available.
I don't get the Mexican reference. What does this have to do with Mexico or Mexicans?
Looks like Mr. Rafael is from Mexico. (see second to last paragraph of ible)
You got that right, sir ! I am from Mexico.

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