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  #1  
Old 09-27-2007, 06:23 PM
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Cool Amps To Kilowatts

How Do You Determine Kilowatts From Amps? I Have 288 Amps How Do You Determine How Many Kilowatts That Is?
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  #2  
Old 09-28-2007, 10:00 AM
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Default Re: Amps To Kilowatts

What Voltage are you assuming?


The conversion of Amps to Watts is governed by the equation

Watts = Amps x Volts

For example 1 amp * 110 volts = 110 watts


In your case I will assume 110 volts so:

288 * 110v = 31,680 volts

or

31.68 Kilowatts
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Old 10-02-2007, 12:17 AM
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Default Re: Amps To Kilowatts

You made an error in the reply that makes it confusing
288A * 110V = 31,680 Watt

but 288A on a 110V grid is unlikely; I would expect it is 480V in a three phase grid; that makes it even more difficult :-)
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Old 10-02-2007, 09:57 AM
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Default Re: Amps To Kilowatts

Quote:
Originally Posted by Unregistered
You made an error in the reply that makes it confusing
288A * 110V = 31,680 Watt

but 288A on a 110V grid is unlikely; I would expect it is 480V in a three phase grid; that makes it even more difficult :-)
That was just an example of the arithmetic.
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Old 11-21-2007, 04:55 AM
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Default Re: Amps To Kilowatts

Quote:
Originally Posted by Unregistered
How Do You Determine Kilowatts From Amps? I Have 400 Amps How Do You Determine How Many Kilowatts That Is?
at 3phase 208volts




I Have 400 Amps How Do You Determine How Many Kilowatts That Is? at 3phase 208volts
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  #6  
Old 11-20-2008, 03:16 PM
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Default Re: Amps To Kilowatts

400amps @ 3p208

400*(3*208)=249,600w

249,600/1000=249.6
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  #7  
Old 04-10-2009, 02:55 AM
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Default Kilowatts to amps

i hav motor for machine 380 v /3 phas /30 kw i whant know how many amps this motor ned
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Old 04-10-2009, 04:14 AM
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Default Re: Kilowatts to amps

Quote:
Originally Posted by mohamed
i hav motor for machine 380 v /3 phas /30 kw i whant know how many amps this motor ned
The question is whether the 380 V is measured line to neutral or line to line. If it is line to line, then it is only 219 V line to neutral.

I will assume it is line to neutral
30 kW/380 V = 78.9 A
That is the sum of the three phase currents, each phase is 26.3 A, assuming the load is balanced.
(It may need higher current during starting.)

Edit: It is actually more likely that it is 219 V line to neutral and 380 line to line.
30 kW/219 V = 137 A, 45.7 A in each phase (assuming balanced load)

Last edited by JohnS; 04-10-2009 at 05:34 AM.
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  #9  
Old 04-13-2009, 05:39 AM
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Default Re: Kilowatts to amps

Quote:
Originally Posted by JohnS
The question is whether the 380 V is measured line to neutral or line to line. If it is line to line, then it is only 219 V line to neutral.

I will assume it is line to neutral
30 kW/380 V = 78.9 A
That is the sum of the three phase currents, each phase is 26.3 A, assuming the load is balanced.
(It may need higher current during starting.)

Edit: It is actually more likely that it is 219 V line to neutral and 380 line to line.
30 kW/219 V = 137 A, 45.7 A in each phase (assuming balanced load)
A three phase induction motor would be running phase to phase (no neutral required). The calculation is: 30,000W/380V/1.73 (sqrt of 3) or45.58028441
Amps. That being said, overcurrent protection will have to be sized to carry momentary starting load of about 250%. This could be even higher in an application with large inertial loading. The calculation is assuming 100% efficiency as well, so you need to know if 30kW is the size of the motor or the consumption under load and divide the current figure by efficiency.

Note that the square root of the phasing is used as actual voltage (an hence current) in a three phase circuit is 120 electrical degrees apart so the actual currents peak 1/150 of a second apart in 50 Hz or 1/180 of a second at 60 Hz.

Motor name plate data should indicate FLA (full load amps) and LRA (locked rotor amps). Local code requirements or good engineering practice will dictate wire size and overcurrent protection.

Sounds like you are looking at wire in the #6 AWG range (~15 sq mm) with an increase in size of (~5 sq mm) for each 30m increase in length.

Of course that's looking at it from half a world away.

Last edited by MJWorner; 04-13-2009 at 05:59 AM.
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  #10  
Old 04-13-2009, 05:59 AM
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Default Re: Amps To Kilowatts

Quote:
Originally Posted by Unregistered111
400amps @ 3p208

400*(3*208)=249,600w

249,600/1000=249.6
That should be 400A x sq rt 3 (1.73) x 208V = 144,106.63 W or 144.1 kW.

You have to take the square root of the phases because they don't peak simultaneously but sequentially 1/180 of a second apart.
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