Question

The primary winding of the welding transformer has 1000 turns and the secondary winding 110 turns. It is connected to the mains at a voltage of 230 V, giving a secondary current of 120 A. Assume an ideal welding transformer.

a) What is the primary current? How big a fuse should there be behind the socket to which the welding transformer is connected - which of the 10 A, 16 A or 20 A fuses is large enough?

b) What is the secondary voltage?

c) Why is the secondary current in the welding transformer desired high?

Answer 1

Gives

$N_1=1000\\N_2=110\\V_1=230V$

$I_2=120A$

Part(b)

$\frac{V_1}{V_2}=\frac{N_1}{N_2}\\V_2=\frac{N_2}{N_1}\times V_1$

$V_2=\frac{110}{1000}\times 230$

V₂=25.3V

Part(A)

$I_1=\frac{N_2}{N_1}\times I_2$

$I_1=\frac{110}{1000}\times 120=13.2A$

Part(c)

big a fuse should there be behind the socket to which the welding transformer is connected 10 Amp

$I_2=120A$ then turn $N_2=110$

High current flow in low turn transformer

$I\alpha \frac{1}{N}$

Current inversely proportional to turns