Welding Machines

Characteristics of A.C. Welding Machine: 

• A.C. welding machine is cheaper, small in size, light in weight, and simple to operate.
• Maintenance of A.C. welding machine is easier and more economical because there is no moving part in it.
• The heat generated is equal at both the poles, so it does not require changing of polarity.
• A.C. welding machine is not suitable for welding all metals particularly non-ferrous metals and alloys.
• The bare electrode cannot be used. Only specially designed coated electrodes can be used.
• A.C. welding machine is not suitable for welding sheet metals due to difficulty in starting the arc.
• The problem of arc-blow can be easily controlled.
• Voltage drop in A.C. is less, hence, can be used at large distances from the power supply.
• It can only be used when A.C. power supply is available.
• Less electric energy consumption per kg of metal deposited (3 to 4 kWh.).
• A.C. Welding machine has high efficiency (0.8 to 0.85).
• It has a lower operating cost.
• A.C. Welding machine has a disadvantage of using low power factor at the welding station, (0.3 to 0.4).

Characteristics of D.C. Welding Machine:

• D.C. welding machine is two to three times costlier, larger in size, heavier in weight, and is more complicated.
• Maintenance cost is higher because of the many moving parts in it.
• The heat generated is different at the work and the electrode by changing the polarity.
• D.C. welding machine is suitable for welding all types of metals by changing the polarity.
• Both coated and bare electrodes can be used in D.C. welding machines.
• It is used for all sorts of work as starting the arc is easier comparatively.
• Arc-blow is severe and difficult to control.
• Voltage drop is relatively higher, it can be used only at a short distance from the power supply.
• It can be used anywhere with an engine-driven D.C. generator or by rectified A.C. supply.
• Higher electric energy consumption per kg of metal deposited (6 to 10 kWh).
• The efficiency of the D.C. Welding machine is low only 0.3 to 0.6.
• It has a higher operating cost.
• The motor in a D.C. Welding has an advantage of a high power factor of 0.6 to 0.7.

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