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# Amps on three phase to house etc.

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#### SimonTHK

##### Member
Hello smart people
I noticed that on my machine, it says that it uses 400 v, 24.5 amps, 17kw. So that doesnt work in ohms law
I did use an online calculator, and the information seems to be right.
Sooo I have 3 of these machines, but only 65 amps input to my house (workplace). I guess I cant have all 3 machines running, without more power delivered to the house, since they will use 3x24.5= 73.5 amp together?

What machine? Some machines pull much less power most of the time. I am thinking about saws. The 17kw is probably at max load. If I turned on every machine I will pop the breaker but I keep most machines off line.

It's not Ohms law. That relates to resistance. I don't think that there's a name for power = volts*amps

Anyhow, the 400 V on three phase is measured between phases, so it's only 400 / sqrt(3) = 230 V. So a 3-phase 400 V supply is just three 230 V ac supplies, which is why something like this:- https://www.titanpower.co.uk/32a-415v-adaptor-3-x-32a-240v-out.html can exist without electronics or transformers.

So the power is 230 * 3 * 24.5 = 16905 W so it does work out to the correct power, near enough.

You are correct that you can't have all 3 running on a 65 A feed, however the rating might be the maximum and they might take a lot less most of the time.

What sort of machines are they? For motors, the power is often quite a lot less than the current times the voltage, because the current that they take isn't in phase with the voltage. That is why kW and kVA are quoted separately.

And......
Don’t forget to multiply the result of the volt-amps by the power factor to obtain true watts.

In general - for question regarding motors it can be a good idea to upload a picture of the machine rating plate. And as mentioned - the full name and manufacturer of the machine/equipment itself.

Ah ok thank you Diver.
The machines are fryers. Professionel ones. They use contactors. So basically they will use maximum power whenever all heating elements are turned on. And that will be quite often.
I guess I need more power.

All or nearly all the power that fryers will be the heaters, so that is why the power factor is 1.

It does seem that you will need more power.

Yes
Thank you all, I just needed to be sure that this could really be right. Right now I have ton of machines, but dont use 65 amps. So that 1 fryer can use 75 amps, is wild. Nonetheless true. Simply because it is a super heavy duty fryer.

Yes
Thank you all, I just needed to be sure that this could really be right. Right now I have ton of machines, but dont use 65 amps. So that 1 fryer can use 75 amps, is wild. Nonetheless true. Simply because it is a super heavy duty fryer.

I did a delivery of a new oven to a guy a couple of years ago, he'd recently retired from his job, and he mentioned that the last thing he did was buy a new oven at work before he retired.

However, the one at work cost £4,000,000

He worked at a biscuit manufacturer, and it was 100m long and cooked the biscuits as they travelled through.

I imagine that took a LOT more than 75 amps - so a commercial fryer doesn't surprise me.

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Crazy yes. And ovens use extremely much power.
The fryer I bought used, cost new 80.000 dollar. I guess that is also quite alot

Crazy yes. And ovens use extremely much power.
The fryer I bought used, cost new 80.000 dollar. I guess that is also quite a lot

Oh yes - QUITE a lot

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