Working out the current per phase of generator

[myristate]

Anybody know how to work out the current for each phase of a generator. The generator in questions is three phase producing 8500 Watts and at 415V. trying to work out how many amps per phase. Tried to find the formula but cant seem to find it.


Also anybody able to work out what the full load current of a three phase squirrel cage motor rated at 2200 Watts and 415V

 

[Knobhead]

Homework?

 

[myristate]

No not homework, My father is a spark as well as me but the internet is beyond him. He used to specialise in motors and generators But hes been retired for 20 years. I dont know what hes doing with them but he has asked me if i can help him find out the info

 

[davesparks]

the laws of physics haven't changed much since he was specialising in motors and generators so the calculations he used back then will still work now.

 

[myristate]

If he could remember I am sure he would of not asked for my help

 

[Simonslimline]

Watts/(1.732 x 415 x pf ) ?

 

[Knobhead]

You’re right with the ? bit.

 

[Silly Sausage]

3 phase calcs scare the living daylights out me...where does that root 3 go?
415V, old question.

 

[Simonslimline]

Edit ....

 

[Knobhead]

Simon, I notice you’re a trainee. Do you expect members of the forum to do your homework?

Why do you try to do someone else’s work?

 

[Simonslimline]

Forget it I am talking rubbish anyway. I just looked through my notes :leaving:

 

[Darkwood]

I use a 2 second quick rule of thumb for small 3ph induction motors that accounts for average efficiency and a power factor of approx 0.8..... simple take the Kw rating and double it to give FLC current ... so 2.2Kw would be 4.4amps

Note its a rule of thumb and works well for squirrel cage 3ph motors up to 30Kw but for your final calcs use the proper method.

PS ... just a rule of thumb and not to be used to work your OL setting or cable sizing ...I use it for quick response to customer.

@The OP ... Ok your old man cannot remember or has a computer but you have internet access and just typing in on Google what you are asking brings hundreds of options with the answer....

 

[Knobhead]

I just use a spreadsheet.

 

[Darkwood]

The only sheet I spread has a useful function in my bathroom .... My ickle rule of thumb is good for instant response to customer ...telling him the FLC on the motor plate before either of you look gives him confidence in you competence Ive found ....especially after you show him the correct method of calc's and say you did it in your head

 

[Guest111]

assuming a power factor of 0.86 then Kva =Kw/pf therefore 2.2 kW/3=0.733/0.86=852Va current=VA/V=850/230=3.704A per phase.

 

[ayjay]

just start the thing up, connect it
if its not sutable get a bigger one
stop worrying, by the time youve asked on here someone else will have poached the job mate
btw has dad lost the p--- no ill get chucked off again

 

[Darkwood]

assuming a power factor of 0.86 then Kva =Kw/pf therefore 2.2 kW/3=0.733/0.86=852Va current=VA/V=850/230=3.704A per phase.

+ motor efficiency

 

[Guest111]

+ motor efficiency

correct but it's late and I've had a few.lol

 

[Darkwood]

correct but it's late and I've had a few.lol

Same here .. bed calling but won the quiz tonight :rockon2: .... free beer ahead woohoo!!

 

[Guest111]

Same here .. bed calling but won the quiz tonight :rockon2: .... free beer ahead woohoo!!

yeah me too,might work out tomorrow how far out I was with those calcs.