How to Repair an Inverter Welding Machine
Welding machine repair is possible for most types of welder failures, damages, and faults. However, only qualified and knowledgeable technicians should test, repair, and maintain welding power sources. Welders are high-voltage equipment with complex internal circuitry. Electric shock from a welder can cause severe injury, burns, and lead to fatal outcomes.
How Transformer and Inverter Welders Work
Transformer-based welding power sources and inverter welders have certain similarities and differences. But to understand inverter-based welders, it's critical to know how a simple transformer-based welder works.
A welding transformer receives the electrical current from the mains outlet in your shop and uses it to produce controlled low-voltage output. Essentially, all transformers have the following three components with their corresponding use:
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Primary coil - Receives the mains voltage.
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Secondary coil - This winding is connected to the output terminals (ground clamp and the torch/electrode holder). It receives the induced current via a magnetic field from the first coil.
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Core - Steel laminated sheets that concentrate the magnetic field produced by the first coil into the second coil. This steel core must be sized correctly to concentrate the magnetic fields to work with the 50/60Hz AC input from the wall, which is why transformer-based welders are so heavy and large.
Once the electrical current enters from the outlet into the first coil of the transformer, it produces a magnetic field around the wire. The iron/steel core concentrates the field, while the secondary winding receives the current.
However, the number of windings of each coil is the key in controlling the electrical current output. A step-down transformer has fewer windings in the secondary coil, which causes the volts and amps to "switch places." The energy stays the same, but the input voltage/amperage changes into different values on the output side.
For example, if you plug a welder into a 220V outlet at 30A, the step-down transformer will output 220A at 30V. These are basics of how transformers work, but there are more nuanced details and methods of output current control we can't go into in this brief overview.
An inverter-based welder also has a transformer inside, but it's drastically smaller and lighter. While a transformer in the transformer-based welder can weigh tens or hundreds of kilograms, inverter-based machines use transformers that can fit in the palm of your hand. That's why they are so efficient and lightweight.
Inverter welders use solid-state IGBT controllers to change the incoming 50/60 Hz AC current from the wall into significantly higher frequency (thousands of cycles per second). As a result, the steel transformer core can be dramatically smaller, allowing for a much more compact machine design.
Common Causes of Welding Machine Breakdowns
Besides transformers and solid-state inverter controllers, welding machines also use rectifiers, capacitors, resistors, microprocessors, specialised diodes, relays, and many other electrical components for precise current output, especially modern welders with pulsing capabilities. There are many things that can go wrong with a welder, from a burnt resistor to a breakdown in the insulating material of the transformer core.
Besides electrical faults, welding machines can have issues with wire-feeding equipment, torches, leads, gas valves, and settings panels.
Some of the most common causes of welder breakdown are:
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Poor maintenance schedule - Maintenance is critical for the machine's longevity. Cleaning the terminals, removing the dust build up, maintaining drive rolls, and inspecting cables and hoses go a long way in keeping your welder working correctly.
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Excessive heat - Internal parts of the welder get very hot during welding, which is why the manufacturer's rated duty cycle rules should be followed. Usually, welding equipment auto shuts down if overheated. But this auto feature may not always save the welder in time, especially if it's frequently pushed over its limits. Excessive heat can break down the insulation material of critical components inside the unit and burn chips and other sensitive circuitry elements.
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Dust build-up - Excessive dust inside the welder can prevent airflow and clog up the radiators. Likewise, thick dust covering the PCB acts as a blanket, further preventing heat dissipation from sensitive parts.
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Non-operational fan - If your fan breaks or stops spinning, you shouldn't use the welder until it's repaired. Cooling fans are critical for heat prevention.
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Condensation - Welding at low temperatures is also a problem. If the machine becomes too cold, the moisture from the air will condense on the PCB. As a result, tiny water droplets can short-circuit sensitive chips, leading to equipment failure.
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Aggressive environments - Welding equipment used in the offshore, oil and gas, petrochemical, marine, and construction industries are at an increased risk of internal and external corrosion and dust build-up. You may need to increase the maintenance frequency when the equipment is used in high humidity, high dust, and high saltwater environments.
Examining a Faulty Welding Machine
Before any repairs can be done, examining the faulty unit is a crucial step and we always recommend seeking a qualified technician to carry out this process. Static electric damage can occur, leading to additional damage if this step is performed incorrectly. Likewise, an inexperienced person could easily receive a fatal electric shock from the welding machine components once the machine's cover is removed. Only qualified persons should attempt to repair welding power sources, and they must follow their local codes for safely working with electrical equipment.
There are many ways an unaware person can get harmed trying to repair the internal circuitry. For example, an electrolytic capacitor could provide sufficient electricity for severe electric shock, even if the unit is powered off. Technicians use specialised resistors and other tools to discharge powered elements before the work can begin. Working on an energised unit (when necessary) requires following a set of safety procedures and significant experience, as one wrong move can severely harm the technician.
Modern inverter welders require additional precautions. Incorrect part installation and repairs can cause installed parts to explode or lead to an explosion of other parts on the board.
Our team of experienced technicians can inspect, diagnose, and fix almost any issue with transformer and inverter-based welders and engine-driven welding machines.
Common steps during the examination phase are:
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Powering down the machine.
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Checking for bare wires, obvious shorts, corroded connections, burned contacts, and loose connections.
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Inspecting the wire feeding unit, leads, hoses, and torch for damage.
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Ensuring the internal safety ground circuit is securely connected.
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Vacuum or air compressor is applied internally to clean the dust build-up.
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Visual inspection of internal components for loose connections, burns, exposed wiring, and shorts.
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Inspecting for signs of overheating and checking the insulating material condition.
There are many more steps qualified technicians will take depending on the fault type. After the initial inspection, the technician will use tools like digital multimeters (DMM) to test and troubleshoot the electrical connectivity of each element inside the unit until they pinpoint the problem. This is not recommended for unqualified persons. It's easy to get electrocuted if you use DMM incorrectly. Accidentally shorting the circuitry with a DMM can cause injuries and lead to additional parts breaking down. Likewise, it requires experience to know how to calibrate the DMM before testing. Improper DMM setup can cause injuries, damage the DMM, or have you incorrectly diagnose the issue.
Static electricity is also an issue when working with the exposed internals of an inverter-based welder. It can cause injury due to shock and lead to damage of CMOS, IGBT, MOSFET, E-proms, Op-Amps, and other sensitive parts of an inverter welder. Qualified technicians know how and when to wear a grounded wrist strap to prevent static electric shock. However, the wrist strap must never be used with powered welding equipment.
Welding Machine Repair - The Final Step
Once the machine is diagnosed and the issue is pinpointed to a single or multiple failed parts, they can be replaced if replacement parts are available. Depending on the brand and make, sometimes it may not be economically viable to attempt a repair, but repairs are an option for most welding brands.
Mechanical repairs like replacing a faulty wire drive system or failing torch components are less challenging to perform. Usually, the most complex repairs are inside the welder. Replacing faulty resistors, capacitors, diodes, microprocessors, IGBT controllers, and similar parts is more challenging and requires following strict procedures to achieve long-lasting repairs.
Most internal circuitry repairs require soldering equipment. Once you locate the faulty parts through testing, they can be removed from the PCB, and new ones can be soldered in their place. It's critical to solder the connections properly without shorts and to install suitable replacement parts. Incorrect part selection can lead to additional damage and operator injury.
Trust Alphaweld Experienced Repair Technicians for Your Welding Machine Repair
If you are experiencing issues with your welding machine or want to schedule a maintenance check, Alphaweld is here for you. Submit a service request and our team will walk you through the steps to having your machine repaired.
To speak with an expert, call (08) 9456 8000 or send us an online enquiry and we'll be happy to assist.
Disclaimer: The information in this article is intended to provide general information designed to help users understand the repair process of an inverter welding machine. It is not in the nature of professional or legal advice. While every effort is taken to ensure the information is accurate, we do not represent or warrant that this information is correct, current, complete, reliable or suitable for any purpose and it must not be relied on by you or any other person as a substitute for appropriate and independent professional advice. For your personal safety and the safety of others, we strongly recommend seeking a qualified repair technician for all welding machine repairs.