Recommendations for the repair of inverter welding machines

A welding inverter, like any other equipment, may fail sooner or later. And if this happens, the problem can be solved in two ways: return the device to a service center specializing in repair of inverter welding machines, or try to fix the problem yourself.

Welding machine repair

Before repairing a welding inverter, make sure that it is disconnected from the power supply.

Having mastered the necessary information, you will be able to fix some faults with your own hands, without resorting to the help of masters. This, of course, will save you money. However, the time may take a lot. Consider how to repair welding machines with their own hands and what malfunctions occur most often.

Features of welding inverters and their repair

Electric circuit welding inverter

Electric circuit welding inverter.

Inverter welding machines make it possible to perform high-quality welding with maximum comfort, while having minimal skills to work with it.

The welding inverter is characterized by a more complex, but less reliable design than that of welding transformers and rectifiers. An inverter, unlike its electrical predecessors, is a rather complex electronic product. If the inverter unit stops working, then the first thing to test is whether the working diodes, stabilizers, transistors and other elements of the inverter welding circuit. To do this, you must be able to use a voltmeter, multimeter and oscilloscope.

Inverter welding has its own characteristics during repairs. For example, it often happens that it is not possible to immediately identify the non-working part and it is necessary to check every element of the apparatus. Therefore, in order to properly repair an inverter, it is very important to have at least basic knowledge of electronics and skills in working with electrical circuits. If you do not own this knowledge, then it is better to give the inverter for repair to specialists. Otherwise, you will simply lose time and energy or even aggravate the situation.

Each inverter must be accompanied by instructions that list possible malfunctions and recommendations for eliminating them.

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Diagnostics of malfunctions of welding inverters

Power supply inverter welding machine

In the power supply unit of the welding inverter most often fail capacitors.

Before you start repairing inverter welding, you should know what the main types of faults are.

First, a visual inspection of the device.

If there are places with broken contacts, the parts must be disconnected, cleaned and reattached.

The most vulnerable places of the welding inverter is the terminal block. It connects the welding cable.

High current and poor contact lead to heating at the junction of the wires, which can be critical for the device.

There are several groups of all faults in inverter welding machines:

  • the malfunctions arising at a wrong choice of an operating mode of welding;
  • breakdown or incorrect operation of the electronic parts of the inverter welding.

In both cases, welding is either difficult or impossible at all. There are several factors contributing to the occurrence of faults.

They need to be diagnosed sequentially, starting with simple operations and ending with complex ones.

Control unit welding inverter

When testing the welding inverter control unit, special attention should be paid to the induction coils of the voltage regulator.

If all the recommended checks and tests have been performed, and the cause of the breakdown has not been identified and corrected, then the inverter module circuit has most likely been damaged.

Causes of electrical circuit failure can be:

  • moisture ingress inside the device (operation of the device during precipitation);
  • dust accumulated inside the housing of the apparatus leads to disruption of the normal cooling of the elements of the electrical circuit (usually this happens during continuous operation at construction sites);
  • Inverter overheating due to improper operation.
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The main types of failures of welding inverters and their elimination

In general, breakdowns of welding inverters are the result of the influence of any external factors or errors in setting up and operating the devices.

Elements of the welding inverter

Diagram of the main elements of the welding inverter.

The most common problems:

  1. Unstable arc welding or excessive spatter of electrode material. The reason is the current mismatch between the type and diameter of the electrode and the welding speed. The required current strength can be obtained from the recommendations of the electrode manufacturer, which are indicated on the package. If this information is not specified, then you can use the formula for calculating the current: 20-40 A per 1 mm of the diameter of the electrode. When reducing the welding speed, the current value also needs to be reduced.
  2. Adhesion of the welding electrode to the metal. This may be due to several reasons. In most cases, this happens due to the fact that the device is connected to a network with insufficient supply voltage. This may also be due to poor contact of the modules of the device in the panel sockets. You can eliminate this problem by tightening the fasteners and fixing the boards well. At the input of the inverter, the voltage may drop when using a power extension cord, the cross section of which is less than 2.5 mm2. An excessively long extension cord can also cause a voltage drop (with a wire length of 40 m or more, operation of the device is almost impossible, since large current losses occur in the circuit). The electrode may stick due to oxidation or burning of the contacts in the circuit, which can also lead to a voltage drop. This problem may also be encountered if the materials to be welded are improperly prepared (the contact between the electrode and the part deteriorates if there is an oxide film on it).
  3. Lack of welding when the inverter is turned on and the indicators work. The reasons for this in most cases are overheating of the apparatus and spontaneous disconnection or damage to the welding cables.
  4. Spontaneous shutdown of the inverter. When the transformer is connected to the network, its protection is triggered and the device is turned off. The reason may be a short circuit in the circuit between the wires and the housing. Protection may be activated when a circuit is made between sheets of magnetic wire or coils of coils and the breakdown of capacitors. Remedy: disconnect the transformer from the network, find the defective item and repair it - replace the capacitor, repair the insulation, etc.
  5. Large current consumption with low or no load on the network. A possible reason is the closure of the turns on the coils. The problem is eliminated by rewinding or adjusting the insulation layer.
  6. The cause of shutdown during welding works mains voltage may be incorrectly selected circuit breaker. It should be calculated on a current up to 25 A.
  7. Termination of the inverter in the process of long-term welding. Most likely, the cause of this is overheating. When exceeding the permissible temperature protection is triggered. Wait 20-30 minutes and continue.
  8. The transformer can buzz heavily, which is accompanied by overheating of the device. One of the reasons is the loosening of the bolts that tighten the leafy elements of the magnetic wire. The reason for this may be a malfunction in the fastener core, and an overload of the transformer, and the circuit between the welding cables. Check and tighten all the bolts, repair the core fastening, repair the insulation of the welding cables.

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Recommendations for self-repair of welding inverters

The appearance of the smell of burning from the housing of the welding inverter indicates a serious malfunction and requires qualified repair.

Current conversion in welding inverter

Current conversion circuit in the welding inverter.

Therefore, in this case it is better to contact the masters of specialized service.

  1. To identify and eliminate the cause of the malfunction, you need to open the welding inverter case and inspect its parts. Often the problem lies in the poor soldering of parts and contacts, in order to resume the operation of the apparatus, it is enough to solder the parts in sufficient quality. Broken, cracked and burnt wires and parts, swollen capacitors must be evaporated and replaced with new ones. They should be selected in accordance with the marking indicated on the housing or in the instructions. For watering parts is convenient to use a soldering iron with suction.
  2. If visual inspection did not reveal any visible faults, then the parts and contacts need to be called with an ohmmeter or multimeter. The most vulnerable parts in inverters are transistors. And the audit must begin with them.
  3. Next, check the remaining parts of the board with the tester - printed conductors. Torn off and burnt areas of conductors are removed and soldered jumpers.
  4. Using a tester, you should check all the connectors in the device and clean them with a white stationery eraser.
  5. Input and output rectifiers, which are diode bridges attached to the radiator, are reliable elements of the inverter. However, they sometimes fail. It is better to test the diode bridge after the wires are removed from it and the board is removed. If all the diodes are called short, then you need to find a damaged diode.
  6. At the very end, the key management board is checked. In the inverter welding machines, this element is the most difficult. From his work depends on the functioning of all parts of the welding machine. Also at the very end of the oscilloscope is checked for the presence of control signals that are fed to the bus gate of the key block.

If it was not possible to find the cause of the malfunction or breakdowns more complicated than the cases described above, then you should not try to repair the device with your own hands. It is better to give to professionals who professionally make repairs to the welding machine. Especially if the warranty period has not expired.

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