Difference Between AC and DC Welding | AC vs DC Welding

Welding is a process that uses heat to join metal parts. Are you wondering about the difference between AC and DC welding? You’re not alone. It’s something that everyone has questions about. This article compares these methods as well as gives you an overview of the advantages and disadvantages of each type.

Difference between AC and DC Welding

A comparison between AC arc welding and DC arc welding is provided in the following table.

AC Welding DC Welding
A flux coating must be applied to the electrodes used in the AC welding process. There are no restrictions on the type of electrode that can be used in DC welding.
In AC welding, there is a problem with the stability of the arc. DC welding produces a highly stable arc when it is used to weld.
There is a lack of uniformity in the heat developed. There is a uniformity in the heat developed.
When only an AC supply is available during AC welding, a transformer is required. DC welding requires a rectifier or a motor-generator set when only an AC supply is available.
In comparison to DC welding, the equipment costs are very low. This equipment is very expensive, approximately twice or three times the price of a transformer.
AC welding machines have extremely high operating efficiency (about 80 to 85 percent). DC welding machines have low operating efficiency (about 30 to 40%).
The arc produced by AC welding is controlled automatically. The arc created by DC welding is extremely severe and hard to control.
Poor power factor. As a result of the extremely low power factor (around 0.3 to 0.4), a capacitor is necessary for correcting the power factor. In comparison to ac welding, the power factor in DC welding is high (around 0.6 to 0.7).
When AC welding is performed using a single-phase transformer, the three-phase supply system may become unbalanced. As part of the DC welding process, a motor-generator set is used, which uses a three-phase induction motor that is a balanced load.
The high operating voltage increases the risk of shock. The low operating voltage reduces the risk of shock.
There is less energy consumed in the welding process. The welding process consumes a large amount of energy.
Non-ferrous metals and alloys are difficult to weld due to changes in polarity in the case of AC welding. DC welding can be used to weld any type of metal.
The AC welding equipment is compact and lightweight. The size and weight of DC welding equipment are larger in comparison to DC welding.
There are few maintenances and operating costs associated with AC welding. Due to the presence of moving parts, DC welding has high maintenance and operating costs.
AC arc welding does not suffer from the problem of arc blow. DC arc welding presents a number of problems due to arc blow.

Advantages of AC Welding

1. It is one of the most cost-effective, lightest, and smallest welding machines.

2. An AC machine does not cause magnetic arc blows which are common when welding with a machine that uses DC.

3. There are low operating and maintenance costs associated with AC welding.

4. It is important to keep in mind that the transformer does not have any moving parts, therefore it is quieter and has barely any wear in it.

5. The overall electrical efficiency of the system is quite high.

Disadvantages of AC Welding

1. There is no way to change polarity.

2. Arcs are more difficult to start because of the alternating nature of the current flow, as compared to direct current.

3. The power factor of the system is low.

Advantages of DC Welding

1. When compared with AC welding, DC welding produces less spatter than AC welding.

2. There is a greater degree of stability in the arc produced with a DC supply.

3. It is possible to weld almost any metal, whether it is ferrous or non-ferrous.

Disadvantages of DC Welding

1. There is a high initial cost involved.

2. Costs associated with maintenance are higher.

3. The machine has a noisy operation when it is working.

4. It is the DC welding that causes the arc blow in the welding process.

We hope that this article has cleared your doubt regarding the difference between AC and DC welding. If you have any doubts or queries, feel free to ask. We will be happy to answer your query.

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