# Transposing Formula for Transphormers

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Hello im doing a course in electrical engineering in college, and ive came into a block about working out things on either the primary or the secondary windings of the transformer (Ie, the current, the power, the voltage, or the Turns.)

Now i don't know if this is an American forum or a universal one or a UK site, what ever, In the UK, .Voltage = V .Current = I .Turns = N .Power = P

Im alright in questions such as ...

Eg.If the primary winding has a voltage of 100v and secondary winding has a voltage of 200v and the Current on the primary winding is 30Amps what is the current equal to on the secondary windings,

I can do these with ease, its when it gets to questions that require transposing formula i do struggle especially this one, im not sure about any of it, or how power comes into this equation

Vp/Vs = Ip/Is = Np/Ns

EG. If the voltage and Turns is on primary coils are equal to 300volts and 200N

And the power and current on the secondary coils are equal to 7.6Kv and 100Amps

Could be a number of things such as Working out the voltage or the Turns on the secondary coils or working out the Current or Power on the primary but im not quite sure how i work this 1 out.

(Key: p = Primary s = secondary)

I know That Vp/Vs = Ip/Is = Np/Ns

lecturer didn't make a very good job of explanation lol

Please reply asap Thanks, any help would be appretiated i hope my examples arent to bad, i know they wont work out right but just as an example.

ALSO!, Do you know of any site that has, Questionnaires or Quizzes about transformer equations and such like, im not looking for University stuff just basic level if that exists

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Remember P=IV so if you know the current and the voltage you can work out the power on both the primary and secondary sides of the tranformer. Power does not fit into the transformer equation and must be worked out seperately.

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What about the rest of it lol, how do i work out the current on the Primary if i only know what it is on the secondary. or the Turns or the voltage.

Merged post follows:

Consecutive posts merged

What about the rest of it lol, how do i work out the current on the Primary if i only know what it is on the secondary. or the Turns or the voltage. Thank you by the way though tht was a quick response

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Well its a ratio. So The number of coils in the secondary divided by the primary will give a constant. Say the number of coils in the secondary was 300 and the number of coils in the primary was 150. The the constant would be 2. If you know the current in the primary you can then multiply it by two to get the current in the secondary or if you have it for the secondary you can divide it by two to get the current in the primary. Note the ratio does not work for the power.

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Right, so how would i get the Number of Turns on the Secondary if i only had the primary?

Also, would this work for the voltage?

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Do you know the current or the voltage for both the primary and secondary.

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This is an example of what im talking about, Primary winding: 100v 400N Secondary winding: 200A 1.6Kv

V1 = 100

N1 = 400

I2 = 200

P2 = 1.6kv

This is an Example of an equation i had in class, i dont have any examples with me this is from memory which is why i was looking for a site with some examples and questions

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I take it by P2 you mean power. By the way power can be measured in kilo volts.

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yes power, and what have i been measuring it in?

Power doesn't change right so power in would be the same as the power out?

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Sice P=IV then the power would change would it not because the current and the voltage would be changing. This is how i would do that question -

In secondary -

P=IV

1600=200*V

V=?

So using equation ?/100 = I/200

then you would cross multiply to work out I

Note - the ? is the answer for the voltage which can be found out using the P=IV equation above. The site does not allow you to give answers only help so try doing it yourself.

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This is not some equation thats out of a note book this is just an example i made up. altho i suppose that would be hard to prove this is just me trying to understand this for an upcoming outcome.

So, in reference to this question, what your saying is, P/I = V? or PxI = V?

P2/I2 = V2 or P2x I2 = V2 and from there i would be able to work out the other side simply

eg. N2 = N1 x V2/V1

from there I1 = I2 x N2/N1

and then all left is P1 but i would get that by P=IV so P1 = I1xV1

??? Does that sound Like it ???

Precisely

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Yayy thanks man , do you have "Company of Heroes" by any chance?, or Ventrilo?

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No never heard of them.

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Yayy pass thank you ^^

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