Metal work

Different between DC and AC welding machine

As earlier explained in previous article, welding is a process of joining two or more metal together by melting the base which result to binding when cooled and also using welding filler to form a joint. Metals like stainless steel cannot be weld because it prone to cracking and distortion when heated same with alloys, their melting process has often become a problem because their exact chemical composition are difficult to be known.

AC and DC welding machine

At this end of this article, the reader is expected to understand the difference between AC and DC welding machine and were they are perfectly use.

AC and DC are polarity of electrical current that flows through the electrode. Selecting an electrode with correct polarity determine the strength of the weld because the polarity of the electrode can affect the strength of weld and quality of the weld.

Current is a movement of electrons through a conductor. The alternating current (AC) and direct current (DC) is nothing but the direction of the electrons flow. Their different is just that in direct current (DC) the electrons flow steadily in single direction. While in alternating current (AC), the electrons keep switching direction from backward and then move forward.

Note: Alternating current or AC current flows in one direction half of the time and in the opposite direction the other half. AC current changes its polarity 120 times per second with a 60 hertz current.

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Common differences between AC and DC welding machine.

  1. DC is obtained from cells or battery while AC is obtained from AC generator.
  2. In AC welding machine, the arc-blow can be easily controlled, while in DC arc-blow is severe and difficulty to control.
  3. The frequency of AC welding machine is 50Hz or 60Hz depending upon the country while DJ welding machine have
    zero frequency.
  4. AC can only be used when AC power supply is available, while DC can be used anywhere with engine driven DC generator or by rectified AC supply.
  5. DC flows in one direction in the circuit while AC reverses it direction while flowing in a circuit.
  6. In DC, it passive parameter is resistance only while in AC, it has a passive parameter importance.
  7. In AC, it is easy to be transfer over longer distances and has ability to provide more power while DC cannot travel very far until it begins to lose energy.
  8. DC contains Steady magnetism along the wire while in AC it rotates along the wire because of the direction of flow of electrons
  9. AC welding machine has lower operating cost, while DC has higher operating cost.
  10. AC current of magnitude change with time, while DC current of magnitude is constant
  11. DC are pure and pulsating while AC are trapezoidal, triangular, sinusoidal and square.
  12. DC is always 1 – power factor while AC is positioned between 0 & 1.
  13. AC is cheaper, small in size, light in weight and simple to operate while DC is two to three times costlier, larger in size, heavier in weight and even more complicated.
  14. AC is easier to maintain and more economical because it has no moving parts while DC has high maintenance because of it moving parts.
  15. AC does not require changing of polarity because heat generated is equal at all poles while in DC, heat generated is different with work and electrode which required changing of polarity.
  16. AC types are not suitable for welding all metals like non-ferrous and alloys, while DC is suitable for welding all metals by changing it polarity.
  17. In AC bare electrode cannot be used. It only work with specially designed coated electrodes, which in DC both bare electrodes and coated electrodes can be used.
  18. AC welding machine is not suitable for welding sheet metals due to the difficulties in starting the arc.
  19. AC welding machine is not suitable for welding of sheet metals due to difficulty in starting the arc, while DC is used in welding all sorts of work. The arc is easier to start.
  20. AC welding machine has high efficiency (0.8 to 0.85), while DC welding machine is low efficiency of 0.3 to 0.6.

And that’s it for AC and DC welding machine, i hope you now clearly differentiate between AC and DC welding machine. Well with these 20 differences explained above, i wish you luck!. But don’t forget to share this article with other technical students and please join our comment box.

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