Single-phase Transformer Calculations

[Rhirhi]

Homework Statement

I'm a bit thrown at this problem as I am unsure if firstly my equations so far are correct and secondly where/how I need to factor in the 50 Hz part. Or is this a red herring? Also, am I correct in thinking that the emf means voltage?

Any help would be appreciated

A single-phase transformer having a primary winding of 380 turns is connected to a 400 V, 50 Hz single phase supply.
Calculate:
a the emf induced in the secondary winding of 100 turns;
b the current in the secondary winding if the primary winding carries a current of 20 amperes;
c the number of turns required in the secondary winding to produce an emf of 230 V.

Homework Equations

a[/B]
Vs = Ns x Vp / Np

Vs = 100 x 400 / 380

b.
Is = Ip x Vp / Vs

Is = 20 x 400 / 105.3

c.
Ns = Np x Vs / Vp

Ns = 380 x 230 / 400

The Attempt at a Solution

a. = 105.3 V
b. = 76A
c. = 218.5
[/B]

 

[BvU]

Hello Rhirhi,

What can I say ? To answer your questions:
Equations are correct. You also apply them correctly and do the math correctly.
The 50 Hz doesn't enter in the equations: you can assume the transformer is 'ideal' (no frequency dependence and no power loss).
emf is indeed Voltage.

In PF your part 3 doesn't really count as 'attempt at solution'; you just type the answers.
But all in all: good work !

 

[Rhirhi]

Thanks very much BvU. you have put my mind at rest :-)