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Ideal Transformer Question Help Please

  • Thread starter Physicist3
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  • #1
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Homework Statement



The Mag FLux Density in the core of a 4.4kVA 440V/4400V step up TX is 0.8T (rms). If the induced emf per turn is 10V, find: a) the primary and secondary turns, b) The cross sec area of the core, c) the full load current in each winding.

Homework Equations






The Attempt at a Solution



part a isnt hard, as this question is in a chapter dealing with ideal transformers and so The total emf induced is the same as the applied voltage. The Number of primary turns can therefore be deduced by;

Total emf induced/emf per turn = 440/10 = 44 turns in primary,

this can then be done again for the secondary and the resulting value for number of secondary turn is 440.

For the third part, I believe that the primary current = VA/V1 = 4400VA /440V = 10A, anf the secondary current = VA/V2 = 4400VA / 4400V = 1A. This would make sense based on all the above calculations for turns etc.

I would like some help with the second part of the equation, as i cannot understand how it can be solved using the emf equations for a single phase transformer, as there is no frequency given??

Thanks
 

Answers and Replies

  • #2
rude man
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Homework Statement



The Mag FLux Density in the core of a 4.4kVA 440V/4400V step up TX is 0.8T (rms). If the induced emf per turn is 10V, find: a) the primary and secondary turns, b) The cross sec area of the core, c) the full load current in each winding.

Homework Equations






The Attempt at a Solution



part a isnt hard, as this question is in a chapter dealing with ideal transformers and so The total emf induced is the same as the applied voltage. The Number of primary turns can therefore be deduced by;

Total emf induced/emf per turn = 440/10 = 44 turns in primary,

this can then be done again for the secondary and the resulting value for number of secondary turn is 440.

For the third part, I believe that the primary current = VA/V1 = 4400VA /440V = 10A, anf the secondary current = VA/V2 = 4400VA / 4400V = 1A. This would make sense based on all the above calculations for turns etc.

I would like some help with the second part of the equation, as i cannot understand how it can be solved using the emf equations for a single phase transformer, as there is no frequency given??

Thanks
You have to assume a frequency. Probably 60 Hz. Good point!
 
  • #3
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You have to assume a frequency. Probably 60 Hz. Good point!
This is what I thought, but obviously there are two feasible frequencies that could be used (50Hz or 60Hz), so the accuracy of the answer will therefore be affected. I hate it when text books dont give answers to their questions!!!
 
  • #4
rude man
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This is what I thought, but obviously there are two feasible frequencies that could be used (50Hz or 60Hz), so the accuracy of the answer will therefore be affected. I hate it when text books dont give answers to their questions!!!
Agreed! Where was your textbook published? That might offer a clue as to the intended frequency. What about context (the chapter associated with the problem)?
 

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