Electrical Engineering - Transformers - Discussion

If they give turns ratio in exact value ie,15 then n2/n1 to be consider 15
if they give 15:1, then n1 = 15, n2 = 1 to be considered. If I'm correct please comment.

@dilip.

Ratio given 15:1 so N1/N2=15/1 always, where N1=15, N2=1 then you can apply your formula i.e. N2/N1=V2/V1, except V2 all the others like N2. N1 & V1 known and the answer will be 7. 33V.

How can we know that the given turn ratio is N2/N1 or N1/N2. Why you take N1/N2 as turn ratio in this problem?

K=V1/V2=N1/N2
110/V2=15/1
110/15=V2
V2=7.33

Because 110*15=1650 not given in answer and 110/15=7. 33 is given so we take N1=15 & N2=1 otherwise vise-verse.
In most cases we take turn ratio N2/N1 means N2=15 & N1=1.

N1=15,N2=1,V1=110
If we use N1/N2=V1/V2
and if We use N2/N1=V2/V1
In both cases answer is same
please relax.

In the problem they always give turns ratio as N1:N2. But we have to apply accordingly as per the formula.

Hi guys first tell me the correct formula for step up & down transformer.

@Anu.

Here N1:N2 is 15:1 and V1:V2 is 110:V2.

Here N1<N2 clearly shows that no.of turns at secondary side of transformer is less than primary turns of the transformer which shows that it is a step down transformer.

So V2 should be less than V1=110 Volts.

And also we know that,

Transformer ratio, N1/N2=V1/V2=I2/I1=k.

So from above take only N and V.

So N1/N2=V1/V2.

=>15/1 =110/V2.

=>V2=110/15.

=>V2=7.33333 Volts.

Hope all of you agree this one.

@Anand

Formula for step up and step down transformer is same only.
that is given by,
Transformer ratio ====> K=N1/N2=V1/V2=I2/I1-------(1).

Now this question will be raise in your mind that how this formula came. So here it is:

we know that Energy(power) cannot be created and destroyed but it can be transfer from one form/primary side to other form/secondary side.
So Power P=VI
Then in transformer===> V1*I1=V2*I2.

=> V1/V2=I2/I1 = K(let it be)-----(2).

And also we know that,
In a transformer, Volts per Turn coil is constant on both sides.
So=> V1/N1=V2/N2.

=> V1/V2=N1/N2 = K (from (2))-----(3).

Compare 2 and 3.

Transformer ratio K = V1/V2=N1/N2=I2/I1.