Sparks comp question!

[Simonslimline]

Hi this is another question from sparks magazine competition just wondering what any of you think the answer is. Everyone who has entered has put the answer as 40Amps!!! I have posted this up here as well because more people will see it. (mods please delete the thread from trainee section)

any input on this is appreciated.

Star (VL = ∛ x Vp) (IL = Ip)

Delta (VL = Vp) (IL = ∛ x Ip)

I make the answer 23.09Amps!!! It would only be 40amps if it was Star connected?


Thanks


The line current of a Delta three phase load is 40 A. the current in the phase winding is
a) 70 A
b) 160 A
c) 40 A
d) 16 A

https://www.facebook.com/sparksmag/...1153530230348/826989007313461/?type=1&theater

 

[Morley2012]

I agree with you 40/1.732 = 23.09A but I'm still learning and I was using DIVS and my triangles so I could be wrong.

 

[Pete999]

I agree with your calcs

 

[jimmymac]

Edit...got it wrong

 

[Simonslimline]

(IL = ∛ x Ip), so, ∛ x 40 = 69.28A = 70A....that's how I see it but in have got a severe dust allergy at the moment and can hardly see

But it is saying the line current is 40Amps so the phase current must be smaller 40/1.732.

 

[telectrix]

get a few beers down you. you may still not be able to see, but then you won't want to see anything.

 

[jimmymac]

But it is saying the line current is 40Amps so the phase current must be smaller 40/1.732.

YEP, told ya I couldn't see! I've been trying to edit that for the past five minutes

 

[jimmymac]

I still can't edit it! I agree....23.09A

 

[Lucien Nunes]

The connection to the supply might be delta but that doesn't mean the windings are, as they could be internally star connected if balanced. Possibly a bit of a semantic argument rather than an electrical one.

 

[Simonslimline]

The connection to the supply might be delta but that doesn't mean the windings are, as they could be internally star connected if balanced. Possibly a bit of a semantic argument rather than an electrical one.

I will post up what they say in response. I have emailed them to query the question.

 

[Lucien Nunes]

For my money it's not well worded. You said:

It would only be 40amps if it was Star connected?

But of course it doesn't say 'delta connected' either, only 'delta three phase load.' As 23A isn't a possible answer, we can infer what they meant. Of course if they spelled it out it would be too obvious. I'll give question a B- and move on...

 

[Simonslimline]

For my money it's not well worded. You said:
But of course it doesn't say 'delta connected' either, only 'delta three phase load.' As 23A isn't a possible answer, we can infer what they meant. Of course if they spelled it out it would be too obvious. I'll give question a B- and move on...

My money is on a typo, they may mean star rather than delta. All will be revealed soon

 

[Simonslimline]

So after messaging them, they said it was a typo and are sending me some combination pliers for spotting it :shades_smile:

 

[Chr!s]

There are only four currents to consider in a star connected system, so it must be delta. Assuming a resistive balanced load.

The anwer is Ipl3 - Ipl1


Ill go with 40 amps


Chris

 

[Richard Burns]

So after messaging them, they said it was a typo and are sending me some combination pliers for spotting it :shades_smile:

You will be fully kitted out soon; so long as they keep making these errors!

Not so impressed by the standard of their questions!