Revisiting Pythagoras.

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Hello gentlemen and ladies alike,

I'm priming to take my 2394 and 2395 also with some hope, later maybe the 2396. On side note has anyone done this? What is to be expected? What is it's worth?

Anyway back to what i started this thread for. As i said i've been brushing up on regs GN3 test procedures ect...But as you can guess i get easily distracted.

To the point that i decided to go through my old course notes and books and found a electrical calcs book with exercises and thought ill see if i can still do them.

I found i could until i got to one that should be easy, and no doubt someone/people will tell me my errors but i can't seem to get the given answers in the back of the book.

So for those that are interested, here's the question-

A reactor allows a current of 15A to flow from a 230v, 50Hz supply.

Determine the current which will flow at the same voltage if the frequency changes to

A) 45Hz, B)55Hz. 

Ignore the resistance.

My calcs are as follows-

U/V=XL 

XL=2
6325a65b73ad3051d411effdc6a97e85.png
fL

So, 230/15=15.333

15.333/(2x
6325a65b73ad3051d411effdc6a97e85.png
x50)=0.0488H

And so, 2x
6325a65b73ad3051d411effdc6a97e85.png
x50x0.0488=15.33.

So that bit works out ok.

As far as i can work out i just have to change to the desired frequency to work out the current change.

2x
6325a65b73ad3051d411effdc6a97e85.png
x45x0.0488=13.79ohms

230/13.79=16.67A (book answer = 15.97A)

Same again with higher frequency i get 13.64A (book answer 13.07A)

I've tried the calc again using the alternate Hz to attain the H, but this didn't work out neither.

I don't know why i'm so bothered, i shouldn't care less, but i do, i hate admitting defeat, as in the past i would have had to work this out.

Unless the book is wrong, it which case it'll be smoked....

Am i asking to be flamed? i wonder.....

 
Ball bags, i need to edit the title.

I've no idea why i related it to pythagoras.

I guess i should give up now.

 
2394/2395 I'm in the same boat pal doing them in 2 weeks need some info on them if poss cheers craig

 
Everthing you need is in guidance note 3.

also do the past papers and have a read over the chief examiners reports. They give lots of pointers.

Its also worth getting the 2394/5 exam success book. Gives sample questions and model answers to both the multi choice and written papers.

 
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