In part 3 of the Gas Metal Arc Welding (GMAW) blog, we will discuss the power circuit.

Often people forget the basics when setting up gas metal arc welding machines, it’s these basics that create a lot of frustration with welders.

Welding is complex but it doesn’t have to be difficult if you understand how a machine works.

This blog breaks it down the main elements of the GMAW power circuit and discusses issues that may arise and how to troubleshoot them.


Power circuit

A common thing people have problems with is the power supply.

If you are experiencing issues with power, the first thing you need to do is ensure all of your connections are tight. Some of these checks will need to be done by a licensed electrician for safety and accuracy. For example, the cable connecting the three-phase plug, which is known as the primary cable, and connections inside the power source body requires an electrician.

You need to ensure that all connections are tight and in the correct polarity so the machine or power source receives the correct amount of electricity.

Three phase connection

Three phase connection



You need to inspect the pins on the three-phase plug to ensure there is no evidence of earthing or arcing. Incorrect connection of the three-phase plug can cause sparking, which damages the power source. This damage creates issues with what is effectively known as clean power.

The connections on the secondary side or output side should also be checked. Inspect them thoroughly to make sure the connections are of the right type and are tight. This ensures you are getting all of the available power transferred from the power source into your machine.

Work return lead connection

Work return lead connection


Loose connections

The connections including both electrode and work return (often called earth lead) need to be tight. Loose connections create an increase in resistance.

An increase in resistance can cause:

  • reduction of power
  • overheating the insulators
  • damage to the machine

Damage to your machine can cause the output terminals to short-circuit to the case of the machine. This is not only costly but also extremely dangerous because the machine body or cables can become live.

You must ensure the output leads are of an adequate rating or they will overheat. As mentioned above, heat causes resistance which results in the erosion of the insulation.

G-clamp type clamps on your work return are far more effective as they generate a more positive connection than spring type clamps.

G clamp type work return lead

G clamp type work return lead



Spring clamp type work return lead

Spring clamp type work return lead


Hidden connections

There are a number of other connections which are not immediately apparent. These connections are located where the output terminal from the power source joins to (what is referred to as) the transfer block.

This is the block or brass connection located in front of the wire feeder, between the drive rolls and the torch. This connection is attached and must be tight, to ensure you have the full transfer of energy from the power source to your feed wire or electrode.

Transfer block

Transfer block


Torch connections

There are many types of torches with each having different connection types. Some of these include:

  • Euro fitting
  • Tweco
  • Bernard
  • Binsel

To get a good weld you must ensure all torch connections are tight as these connections transfer energy or electricity into the torch. This is then carried down to the contact tip and finally to the filler wire. The connection between the wire feed and the torch must have a gas-tight seal. Similarly, the shielding gas must also have a gas-tight seal.

Torch connections

Torch connections


Understand the maintenance

The analogy often used at Technoweld is:

“if a Formula One car driver doesn’t ensure their car is maintained,

they will constantly break down, run poorly and maybe not even finish the race”

For welding applications, if you do not understand how to maintain a machine, you will potentially get poor welds and your arc on time will be reduced, as you are constantly fighting against the equipment.

Welding can be complex but it doesn’t have to be difficult.


Technoweld can help

If you require further information or training on how to properly maintain your machine to get the most accurate and effective weld, contact Technoweld. Our team has a deep understanding and appreciation for high-quality equipment maintenance. Our diligence in this area allows us to weld to standard and to meet quality expectations with every single arc.