Safety Precautions Before Beginning Troubleshooting
Welding power sources utilize high input voltages (220V or 380V) and contain high-temperature elements. Before carrying out any inspections, please ensure:
- Complete Power Disconnection: Turn off the main switch of the welding power supply and unplug the input power cable (for three-phase power, make sure all phases are disconnected). Allow 5 to 10 minutes for internal capacitors to fully discharge—this prevents electric shock from residual high voltage.
- Insulation Protection: Wear insulated gloves and safety shoes, and use tools with insulated handles such as screwdrivers and multimeters. Avoid direct contact with circuit boards or terminal blocks.
- Workspace Safety: Remove flammable or explosive materials (including welding wire and alcohol) from the work area. Ensure sufficient ventilation to avoid overheating during operation.
General Troubleshooting Steps
🔍 Visual Inspection – Start with the Basics
No tools are required at this stage. Focus on obvious issues:
- Input and Output Cables
- Input Cable (Grid Side): Look for damage, wear, oxidation, or loose connections. Replace damaged cables with copper conductors of the same specifications (e.g., at least 4mm² for 380V systems).
- Output Cable (Torch and Ground Clamp): Check for signs of overheating or burns. A loose ground clamp can lead to unstable output—often misinterpreted as a power supply failure.
- Equipment Housing and Indicators
- Inspect the casing for deformation or discoloration, which may suggest internal short circuits or overheating.
- Check indicator lights (“Power”, “Fault”, etc.). If no lights are on, the power switch or internal fuse may be faulty. A continuous “Fault” indicator requires checking the manual for error codes (e.g., IGBT overcurrent or overheating).
- Inspection of Internal Components
Only basic components should be checked at this stage—after removing covers where necessary.- Fuse: Usually labeled “FUSE” near the power input. If the filament is broken, replace it with a fuse of the same rating (e.g., 5A/250V). Never use a higher rating to avoid damaging other components.
- Cooling Fan: After re-powering, observe whether the fan is spinning. If not, the motor or thermal switch may be faulty. Replace the fan to prevent overheating.
🔧 Basic Parameter Testing – Using a Multimeter
Use a multimeter to identify common circuit problems:
- Input Voltage Measurement
Set the multimeter to the AC voltage setting (500V range). For 220V, measure between live and neutral; for 380V, measure between phases. Normal voltage should be within ±10% of the rated value. If voltage is missing or too low, check external power issues (e.g., tripped breakers or faulty wiring) before concluding the welder is faulty. - Output Voltage Measurement
Typical no-load voltages: around 50–80V for manual welding, and 80–100V for TIG welding.
With the machine powered on (and no load connected), set the multimeter to DC voltage (100V range) and measure between the “+” and “–” output terminals.- No voltage indicates an open circuit (e.g., contactor not engaging or loose terminals).
- Very low voltage (e.g., below 30V) suggests failure of the internal power module.
- Testing Key Components
- Contactor: After power disconnection, use the continuity test to check the coil. Replace if open. When energized, check the contacts—lack of continuity may mean oxidation, requiring cleaning or replacement.
- Rectifier Bridge: With power off, use the diode test mode. If there is conduction in both directions—or no conduction in either—between input and output terminals, the rectifier is faulty and must be replaced with an identical model.
⚙️ Advanced Diagnostics – For Complex Issues
If the above steps do not resolve the issue, the problem may lie in internal components such as IGBT modules, control boards, or feedback circuits. These tasks should be performed by qualified technicians:
- IGBT Modules
As core components of inverter welding machines, IGBTs are susceptible to overcurrent damage.
Use the diode test function to measure between the collector (C), emitter (E), and gate (G). If there is conduction in both directions between C and E, the IGBT is shorted and must be replaced. Apply thermal paste during reassembly to ensure good heat dissipation. - Control Boards
- Visually inspect for damaged parts: bulging capacitors, burnt resistors, or poor solder joints. Replace components as needed.
- Use an oscilloscope to examine drive signals (e.g., IGBT gate voltage). If no signal is present, the driver IC or feedback circuit may be faulty.
