Photo AI
Answer any three of the following: (i) Describe the operation of a transformer in electric arc welding - Leaving Cert Engineering - Question (b) - 2020
Question (b)
Answer any three of the following: (i) Describe the operation of a transformer in electric arc welding. (ii) Outline two welding defects that may arise in manual m... show full transcript
Worked Solution & Example Answer:Answer any three of the following: (i) Describe the operation of a transformer in electric arc welding - Leaving Cert Engineering - Question (b) - 2020
Step 1
Describe the operation of a transformer in electric arc welding.
Answer
A transformer in electric arc welding serves to either step down or step up the voltage in a circuit. In a step-down transformer, the secondary voltage is directly proportional to the primary voltage, based on the number of turns in each coil.
For example, if the primary coil has 50 turns and carries 1000 volts while the secondary coil has 10 turns, the secondary voltage can be calculated as:
In practical welding, a variable transformer is utilized to adjust the output by moving the primary coil towards the secondary coil, resulting in a changing voltage.
Step 2
Outline two welding defects that may arise in manual metal arc welding.
Answer
-
Porosity: This defect is characterized by voids or cavities within the weld due to trapped gases. It can occur when moisture is present or during improper shielding.
-
Lack of Penetration: This defect occurs when the weld bead fails to merge adequately with the base metals, often because the welder moves the electrode too quickly or at an improper angle.
Step 3
Explain the difference between a consumable and a non-consumable electrode.
Answer
Consumable electrodes are those that melt and become part of the weld during the welding process, commonly used in methods like MMA (Manual Metal Arc) and SAW (Submerged Arc Welding). In contrast, non-consumable electrodes, such as those used in TIG (Tungsten Inert Gas) welding, do not melt away; instead, they provide the arc necessary for welding while a filler material is added separately.