Calculating amps per phase for 3 phase French supply???

[DaveWalsh]

I have a French ruin with a basic three phase supply rated at 12kW.
I want to run an electric night storage AGA, single phase, rated at 6kW - I calculate this needs a (single phase) 25A supply.
How do I calculate the available AMPS on each of the three phases?
The figures given to me by the girl in the front office at EDF don't seem to make sense!
According to EDFs website the figures are:-
Power 12 kVA - Amps 60
Power 15kVA - Amps 75
If I assume the volts are 230V this doesn't seem to make much sense either!
[/b]Can someone tell me what power I need?
Can anyone throw some light on these French calculations, thanks.

 

[briwire]

The voltage between any of the phases should be about 380v in France. This give about 220v between any phase and earth.

With 3 phase, Power (kW)=1.732 X V X I X power factor

so assuming power is 12000w and power factor is 0.8 which is typical for most loads

12000=1.732 X 380 X I X 0.8

12000 = I X 526.5

I = 12000/526.5

I= 22.8 A per phase

Unfortunately it looks like your 3 phase supply isn't big enough the supply 25A single phase.

 

[DaveWalsh]

Hi , thanks for the reply.
Am I right in thinking that the formula you give:

kW = 1.732 x V x I x power factor

is correct only for balanced three phase loads? If I want to run a single phase 6kW heater (the AGA) on cheap rate overnight electricity then the other phases will be mostly doing nothing - is this OK?

Secondly for a wholly resistive load like a heater element can I assume the power factor to be 1? If so your formula is:-

12000 = 1.732 x 220 x I x 1
I = 12000/(1.732 x 220 x1)
I = 31.4 amps

Does this help me? EDF have been known to take a year or more to uprate domestic supplies.....

 

[briwire]

Your calculations are correct, but there will be a maximum current per phase allowed. You could do with finding what that is. It will be determined by cable size, fuse size, supply transformer size to name a few.

 

[DaveWalsh]

Thanks Briwire,
Getting this information out of EDF should be a trial; blood out of a stone might be quicker. At he moment EDF's technical assistance runs to: "Yes it's a problem for you and others on your line". No hint of when, or if, they can upgrade the supply.