For a DC welding Motor-Generator set, which type of DC generator is used?

• In welding, we use a differentially compound generator because of its drooping characteristics
• The generator used in welding purposes should have high current and low voltage which can be obtained by the differential compound generator
• We can’t get low voltage on high current for a dc shunt generator
• The differential compound generator provides a higher voltage at no load to initiate the arc and once the arc is formed i.e. low resistance and it provides a smaller voltage

Motor-Generator set:

• They consist of a (3-phase) motor, directly coupled to a DC generator
• As the motor speed depends mainly on the mains frequency, these units are relatively insensitive to variations in the supply voltage
• They can be remotely controlled by varying the excitation current
• The efficiency of a welding motor-generator is less and it is in the range of 50 to 60%
• The cost of a motor-generator set is high
• They have good welding characteristics