actual amps

[elevate]

when reading amps on 3 phase for the sake of knowing what the amp draw is are all values added: phase 1 + phase 2 + phase 3 or just take the average of all 3 phases or is it more complicated than I want to know?:

 

[Besoeker]

when reading amps on 3 phase for the sake of knowing what the amp draw is are all values added: phase 1 + phase 2 + phase 3 or just take the average of all 3 phases or is it more complicated than I want to know?:

Probably the latter.

 

[mikeames]

What do you want? The current on each phase, or the current for an entire three phase system? The current on an entire three phase system is a trick question because each phase could be different but the total power consumed can be calculated if you know the phase currents and the power factor. In no situation do you sum the three phase currents or average them.

 

[charlie b]

In no situation do you sum the three phase currents or average them.

I agree that the summation is never a useful number. But I disagree about using the average. For most practical purposes the average value is a good enough number to use. It is not precisely correct, and it gets worse if the phases are out of balance with each other. But it is good enough most of the time.

 

[LarryFine]

But, when it comes to circuit ampacities and the like, the phase with the highest current has to be accomodated.

 

[mikeames]

Fair enough, Ill go with average for an estimate, but not adding.

 

[drbond24]

when reading amps on 3 phase for the sake of knowing what the amp draw is are all values added: phase 1 + phase 2 + phase 3 or just take the average of all 3 phases or is it more complicated than I want to know?:

It depends on exactly what you mean, and I'm not sure I can tell from reading your post. Do you want to measure each phase one at a time with an ammeter, or are you looking at the specs for a piece of equipment that say X number of amps, 3 phase? If you're measuring it then whatever the value your meter is reading is the amperage for that phase. If the equipment says X amps 3 phase, that is the amperage there will be on each phase to supply the equipment (X on phase A, X on phase B, and X on phase C).

In the end, Besoeker had it right, but we might be able to help out a little.

 

[elevate]

On a similar subject a 480 V HPS pole I am to find out what the total amps are being used in order to compare to other type of light fixtures. Amp probe says 1.0 on one leg and 1.0 on the other leg. Is it 2 amps total or just 1.0
the average.

 

[SG-1]

Simular Subject

Simular Subject

I would call that a one amp load.

 

[gar]

091009-2035 EST

elevate:

If you have a two terminal device, such as an ordinary incandescent lamp, then you have a series circuit of one wire to one side of the lamp, the lamp, and the other wire from the other side of the lamp. The same current flows thru each of these elements in this series circuit. You can measure the current anywhere in this series path and the reading will be the same. So as stated by SG-1 your load or lamp current is 1 A.

Now suppose you have a 3 phase Y source with 4 wires, one is a neutral. If you have a load, like one lamp, from one hot wire to the neutral, and no other loads on any of the other hot wires, then this the same as I described in the first paragraph.

Next consider the load of paragraph two, call it load A, and add a different load between one of the other hot wires and the neutral. Now the neutral current will be different than the current thru load A. However, the wire on the neutral side of load A, but not yet part of the neutral will have the same current as the load A.

.

 

[elevate]

Thank you for your help, This information has cleared some of the questions spinning in my head.