Three phase calculation

[m4fiaafg]

Hello everyone please can someone calculate the current for a three phase machine at 28kw unity pf I already I have seemed to forgot how to use the calculator cheers in advance 27kw three phase

 

[Plonker 3]

I see it was a waste of time coming on here not even one decent answer

Erm, we dont just give out this sort of info at will.

You are one of 2 things either a trainee in which case apply to join the trainee section and get help. Or charging for this if this is the case then why should we be esrning your money for you?

 

[GMES]

I see it was a waste of time coming on here not even one decent answer[/QUOTEY

Your Profile says you are an Apprentice if this is the case do you have a mentor to help you with this.
The Guys are more than willing to help people out but you have to meet them halfway, show us your calculations and the Lads will jump in and assist you.

 

[Jonspark]

40.41Amp

 

[Andy78]

I see it was a waste of time coming on here not even one decent answer

"I see it was a waste of time getting this electrician in, he doesn't know how to do one decent cable calculation"
- Your customer

 

[DPG]

I see it was a waste of time coming on here not even one decent answer

Lovely manners. Do visit again.

 

[Simonslimline]

I see it was a waste of time coming on here not even one decent answer

You won't get far with that kind of attitude to be honest. Try showing your calculations first and people will be more willing to help out.

As has already been said, it would be a good idea to get access to the trainee section on here, seeing as you are an apprentice.

 

[Lucien Nunes]

40.41Amp

Too many SF. Do you really know the current to within +/- 10 milliamps using the information given?

 

[Jonspark]

Too many SF. Do you really know the current to within +/- 10 milliamps using the information given?

weve already got

p=28000
u=400
pf=1
and 1.732
so according to the formula isn't that correct, or have I made a mistake some where?

 

[Lucien Nunes]

The answer is numerically correct but as this is possibly a student asking I was suggesting the good practice of quoting the correct number of significant figures in the answer for the accuracy of the given data. 28kW could be 27,500W or 28,499W making the current anywhere between 39.7 and 41.1A at 400V, yet you gave it specifically as 40.41A i.e. between 40.405 and 40.415A. Call me picky if you like.

The funniest one I saw was in a plant handbook where a pump was described as being driven by a 1491.3996W motor. Whoever had the job of doing the metric conversions did not recognise a 2 hp motor when he saw one.

 

[HandySparks]

The answer is numerically correct but as this is possibly a student asking I was suggesting the good practice of quoting the correct number of significant figures in the answer for the accuracy of the given data. 28kW could be 27,500W or 28,499W making the current anywhere between 39.7 and 41.1A at 400V, yet you gave it specifically as 40.41A i.e. between 40.405 and 40.415A. Call me picky if you like.

The funniest one I saw was in a plant handbook where a pump was described as being driven by a 1491.3996W motor. Whoever had the job of doing the metric conversions did not recognise a 2 hp motor when he saw one.

I know what you're saying, but I don't think you should draw ANY conclusion from the number of significant figures shown.

For example if I bought a 3m length of conduit, I wouldn't expect it to be anywhere from 2.5m to 3.5m. And if the conduit was described as 3000mm long, I wouldn't be surprised if it was actually between, say, 2990mm and 3010mm.

You either have to make some reasonable assumptions (which is what all of us do, most of the time), or refer to a relevant standard for manufacturing tolerances, or ask the originator of the figures what the tolerance is in that particular case.

 

[Lucien Nunes]

Your example is a good one and your final point hits the nail on the head. Applying it to the quoted answer would suggest to me that the 4 digit precision given is not appropriate to the source data, regardless of the number of SF in the question. I was just hammering out the implications of this longhand...

 

[DPG]

Let's just call it 40 eh. Daz

 

[Knobhead]

40.41Amp

I suppose you thought you’d look clever in the eyes of the OP by doing his work for him. Your problem now is all that have taken part in this thread have quite the opposite opinion.

 

[Besoeker]

I see it was a waste of time coming on here not even one decent answer

This from Tel:

P=√3VIxpf

isn't just a decent answer. It is the entire answer.

 

[Jonspark]

I suppose you thought you’d look clever in the eyes of the OP by doing his work for him. Your problem now is all that have taken part in this thread have quite the opposite opinion.

Just give em the answer, if they don't want to do the work themselves it'll come back to bite em one day.
That's my view, like it or lump it [emoji6]