Draw schematic diagram of welding transformer showing constructional features of a welding transformer. Also explain its working.
Constructional features of welding transformer:
Working of welding transformer: i) It is a step down transformer that reduces the voltage from the source voltage to a voltage desired according to the demands of the welding process. ii) Winding used is highly reactive or a separate reactor winding is added in series with the secondary winding. iii) Having large & thin primary turns and low number but thick secondary turns. iv) The secondary current is quite high. One end of secondary is connected to welding electrode while other end to the pieces to be welded. v) Due to the contact resistance ‘R’ between the electrode and pieces to be welded a very high current flows creating high heat by I2R that melts the tip of the electrode. The melted tip flows / fills the gap between the pieces to be welded creating a solid weld on cooling. vi) The secondary has several taps for adjusting the secondary voltage to control the welding current. vii) The transformer is normally large in size compared to other step down transformers as the windings are of a much larger gauge. vi) Common ratings: Primary voltage – 230 V, 415 V Secondary voltage – 40 to 60 V Secondary current – 200 to 600 A