Arc welding power sources and current types In arc welding practice, which type of electrical supply can be used to sustain the welding arc and deposit sound metal?

Introduction / Context:This question checks your understanding of arc welding power sources. Arc processes such as SMAW (stick), GTAW (TIG), GMAW (MIG/MAG), SAW, and FCAW can run on alternating current (AC) or direct current (DC) depending on electrode, shielding, base metal, and desired penetration/profile.

Given Data / Assumptions:

• Arc welding requires a controlled current–voltage supply to strike and maintain an arc.
• Different processes/electrodes specify current polarity and waveforms.
• Power-line AC is typically 50 Hz or 60 Hz; high-frequency is used for arc initiation in some processes (e.g., TIG AC start) but is not itself the welding power.

Concept / Approach:The arc is sustained when sufficient current flows through ionized gas between electrode and work. DC (DCEP/DCEN) influences penetration and electrode heating. AC avoids arc blow and is common with certain stick electrodes and for TIG on aluminum (oxide cleaning with AC). High-frequency is often superimposed for arc starting or stabilization in TIG AC, but the welding power remains AC or DC at low frequency.

Step-by-Step Solution:Recognize that many electrodes are rated for DC (e.g., DCEN or DCEP) and others for AC.AC at power frequency is delivered by a welding transformer or inverter; DC is supplied by a rectifier, generator, or inverter.Therefore, suitable arc welding can be performed with AC or DC; selection depends on process requirements.Hence the most general correct choice is that any of these (AC or DC) may be used appropriately.

Verification / Alternative check:Equipment datasheets show SMAW machines available in AC, DC, or AC/DC. TIG for aluminum commonly uses AC with high-frequency stabilization; TIG for steel often uses DCEN. MIG/MAG usually uses DCEP but advanced inverters allow pulsed DC and even AC for specialty applications.

Why Other Options Are Wrong:'Alternating current at high frequency only' is misleading; HF is a superimposed signal for starting/stabilizing, not the main welding power. 'Direct current' alone ignores valid AC cases. 'Pulsed direct current exclusively' is a subset feature, not a universal rule.

Common Pitfalls:Confusing HF with the welding power type; assuming one polarity fits all electrodes; overlooking the effect of AC on arc blow and oxide cleaning in aluminum TIG.

Final Answer:Any of the above, selected to suit the process, electrode, and job