2006-12-21 07:52:46 · 13 answers · asked by mark g 2 in Science & Mathematics ➔ Engineering
120*15 = 1800 watts.
15a is a heckuva lotta current, you know...
2006-12-21 07:56:14 · answer #1 · answered by computerguy103 6 · 0⤊ 0⤋
I can see it requires an expert to answer this problem. Textbooks only go so far, but reality goes further. 120V * 5 Amps = 600VA. (No question about it) No one even thought about power factor. That my friend is.778 multiplier, because you only use about .778 of the 60 Hertz sine wave on the out put. 600 * .778 = 466.80 watts. And of course this equation is designed for switch mode power supplies. This is a good example. Say you are going to buy a UPS for your computer. Your power supply is 450 watts. Is that 600VA UPS, big enough for this system, or would you have problems? Answer, you would have problems. You would say, why? you have 466.8 watts to play with. To expand on this answer, it is very simple. The 466.8 watts is the full load out put when the unit is hot. When the unit is cold, or the transformer windings from the inverter are cold and not on yet, you have induction from the inverter that will chew up 50 watts on a start up. So the equation is not finished yet. You have to subtract 50 watts on the start up of your by-pass of your inverter so the true value is 416 watts on a full load, and you won't get 15 minutes for a run time. Fact is, your inverter will eventually crash and burn with a short life if you constantly drain your battery. Here is something we can add to the equation. Linear power supplies draw 1/3 more power, like telephone systems power supplies. So we have to add 1/3 more to the load that is 600Watts. We need more power. There is absolutely no doubt in my mind that this 600VA UPS will crash and burn in less the 6 weeks or months. APC six weeks, Powerware six months. I would use a 750-watt to 800 watt UPS with a switch mode power supply. On a phone system linear power supply I would use a 1000VA UPS. One last thing. Our constant will always be 120V. Our variable will always be the current draw. So if you use a UPS, make sure that what ever you plug into it, add up all your amp values then mulitiply your voltage and then you will have a VA value. Don't forget the power factor. It will fool you, not to mention if you plug in a wally wart transformer in your you UPS. That ends today’s lesson on UPS and Power. I do take tips, or maybe an apple or two!
2016-03-29 02:54:26 · answer #2 · answered by Anonymous · 0⤊ 0⤋
Power = Volts x Amps
15 x 120 = 1800 Watts
2006-12-21 08:04:52 · answer #3 · answered by efes_haze 5 · 0⤊ 0⤋
It depends on the power factor. If it is a resistive load and is single phase, then power in watts = volts x amps, or 15 x 120 = 1800 W.
If the load is capacitive or inductive. there will be a phase angle between the voltage and the current. In this case, power is equal the the cosine of the phase angle times voltage times current. The cosine of the phase angle is called the power factor.
If it is a three phase load, you have to multiply the result by the square root of three.
2006-12-21 08:34:03 · answer #4 · answered by David H 4 · 1⤊ 0⤋
Simple answer...
volts x current = power
120v x 15A = 1800 watts
2006-12-21 07:58:13 · answer #5 · answered by digidave 1 · 0⤊ 0⤋
P=iE, or Power=Current(amps)xElectromotive Force(voltage)
P=(15)(120)=1800 Watts, or 1.8 Kilowatts. (It's never an exact number however as the voltage is constantly fluctuating)
2006-12-21 07:58:39 · answer #6 · answered by droptoptommy 1 · 0⤊ 0⤋
amps X voltage = watts
15A x 120V = 1800 watts
2006-12-21 07:56:46 · answer #7 · answered by Nick F 6 · 0⤊ 0⤋
Voltage times the current =Watts
2006-12-21 07:55:53 · answer #8 · answered by JOHNNIE B 7 · 0⤊ 0⤋
1800 watts or less depending on the power factor
2006-12-21 08:36:51 · answer #9 · answered by Fool 2 · 0⤊ 0⤋
1800 watts
2006-12-21 07:59:43 · answer #10 · answered by Maid Angela 7 · 0⤊ 0⤋