Probably a Dumb Question, BUT

[R1CH-G]

After a couple of days of intensive cable calcs, diversity, max demand, etc. etc. etc. I have finally managed to disappear up my own jacksie! My head is officially in bits and for the life of me, I cannot get my box round one simple thing.

If a 3 line motor is rated at 60 amps, what is the line current?

I've oficially lost the will to live and going to have a kip in a bucket of homebrew

 

[telectrix]

is it 60A total? what's the kW rating or HP?

 

[R1CH-G]

Not been given kW rating or HP, just that it's a 60A motor. It's a course question on my 2391-20 ~ I don't think this bodes well for the final outcome not being able to work this out

 

[pushrod]

I don't think you have been given enough info and in my limited experience motors are rated in HP or W for output or VA for input, but then you would have to know the efficiency. Also i would have expected to have been given a power factor

Only equation i can think of is IL = P/(√3*VL*PF) but you do not have know enough for that.

If the 60A was a phase current (Ip) then you would need to know if the motor was connected in star or delta.

Be interested to know if you get an answer?

 

[R1CH-G]

Yes, if I had the information to fit it into that formula, there would have been no problem. So probably not a surprise that I was getting nowhere in a hurry.

I think I may have to reverse answer the question, and make a few assumptions!

Thanks for the feedback.

 

[telectrix]

depends which bit of her you want to kiss

 

[ukpablo]

ok the way i read it is with the info given:

star eqn is: IL = IP therefore VL = sqrt 3 x VP therefore transposing gives VP = VL / sqrt 3

IL = 60A then IP = 60A 60A if star

Delta VL = VP therefore IL = sqrt 3 x IP therefore transposing gives IP = IL / sqrt 3

so IL = 60A / sqrt 3 = 34.64A if delta

thats how i read the question anyhow, so hope it has not added to the confusion?