Electrical Engineering - Transformers - Discussion

@ALL.

Turns Ratio = Primary Quantity/Secondary Quantity. Denoted by 1/K. This is applicable to only applied voltage(V), number of turns(N) and induced emf(E). The reverse of this relation gives current turns ratio. i.e N1/N2=I2/I1.

Remember, Turn ratio for a transformer is - K'=1/K=N1/N2=V1/V2.
Where, K'=1/K is turned ratio of transformer and K= Transformation Ratio of Transformer
Transformation Ratio = Secondary Quantity/Primary Quantity=K only

In the given problem, V1=110V and V2=20V. This is correct because for a step-down transformer V1>V2 in relation with N1>N2 i.e No. of primary turns is always proportional to No. of primary voltage and vice versa.

Now, N1/N2=V1/V2=110/20=5.5 => N1/N2=5.5=K' where K'=Turns Ratio of Transformer. Hence Option A is correct. Note:- Please do not confuse with Turns Ratio (K') & Transformation Ratio (K).

The basic formula is
Vs/Vp = Ns/Np where: Vs secondary voltage 20 V
Vp primary voltage 110 V
Ns Secondary turns
Np primary turns

Using the formula gives
20/110 = Ns/Np
0.18 =Ns/Np Remember that turn ratio is Np/Ns
this will give:
Ans: Np/Ns = 5.5 A

* Note: Ns/Np may sometimes use in case of a step up transformer. In this problem it is a step down so Ns/Np is not consider.

The correct answer is 5.5 : 1 The turns ratio is based on the number of turns primary to secondary, the higher the voltage the more turns you have 110/20 = 5.5.

You have 5.5 turns to every 1 turn. Your voltage per turn is the same on your primary and secondary. On your primary you have more turns.

Can anyone correctly give the definition of Turns ratio & Transformation ratio? Is both are the same or inverse to each other? I am very much confused for this two ratios? the above solutions are very much confused. So please help me?

Definition by IEEE.

It is the ratio of a number of turns in the high voltage winding to the number of turns in the low voltage winding.

It is always more than 1.

If you disagree then, Prove me.

Turns ratio = voltage ratio.
N2/N1 = V2/V1.

Where,
V1 = 110.
V2 = 20.

Turns ratio = V2/V1.
= 20/110,
= 0.18.

As the t/f is step down t/f, so the secondary is 20 V & the primary is 110 V.

And according to formula:

Ns/Np=Vs/Vp.

Ns/Np=20/110.

Hence; Ns/Np=0.18.

When i solved the problem i am getting 5.5v
given that v1=110,v2=20
we know,turns ratio means n2/n1
so n2/n1=v2/v1
n2/n1=(110/20)
n2/n1=5.5

Solution:

Primary voltage(V1) = 110V.
Secondary voltage(V2) = 20V.
Turns ratio(K) = N2/N1 = V2/V1.
(K) = 20/110 = 0.18.

To calculate turn ratio, for step down transformer it should be N2/N1.

And for step-up transformer turn ratio should be N1/N2.