Question

Figure shows the core of a transformer and its input and output connections.

1. State the material used for the core and describe the structure of the core.
2. Use the values given in the diagram to calculate the turns ratio for the transformer and connections, labelling all parts of the diagram.
3. If a current of 2 A is taken from the output, calculate the current in the input circuit. (Assume the transformer to be ideal.)

Answer 1

(a) The core is made of soft iron and consists of thin laminated sheets insulated from one another. Laminations reduce energy loss due to eddy currents.

(b) Given: Primary voltage, \(V_p=250\,V\)

Secondary voltage, \(V_s=50\,V\)

Using the transformer formula:

\[\frac{N_{s}}{N_{p}}=\frac{V_{s}}{V_{p}}=\frac{50}{250}=\frac{1}{5}\]

\[{N_p:N_s=5:1}\]

(c) For an ideal transformer, input power equals output power.

\[V_{s}I_{s}=V_{p}I_{p}\]

\[ 250\times I_p=50\times2 \]

\[I_{p}=\frac{50\times2}{250}\]

\[I_{p}=0.4\ \text{A}\]