DIY repair inverter welding machine

In detail: do-it-yourself repair inverter welding machine from a real master for the site my.housecope.com.

Repair of welding inverters, despite its complexity, in most cases can be done independently. And if you are well versed in the design of such devices and have an idea of what is more likely to fail in them, you can successfully optimize the costs of professional service.

Replacement of radio components in the process of repairing a welding inverter

The main purpose of any inverter is to generate a constant welding current, which is obtained by rectifying a high-frequency alternating current. The use of a high-frequency alternating current, converted by means of a special inverter module from a rectified mains supply, is due to the fact that the strength of such a current can be effectively increased to the required value using a compact transformer. It is this principle underlying the operation of the inverter that allows such equipment to be compact in size with high efficiency.

Functional diagram of the welding inverter

The welding inverter circuit, which determines its technical characteristics, includes the following main elements:

a primary rectifier unit, the basis of which is a diode bridge (the task of such a unit is to rectify an alternating current supplied from a standard electrical network);
an inverter unit, the main element of which is a transistor assembly (it is with the help of this unit that the direct current supplied to its input is converted into an alternating current, the frequency of which is 50–100 kHz);
a high-frequency step-down transformer, on which, due to a decrease in the input voltage, the output current is significantly increased (due to the principle of high-frequency transformation, a current can be generated at the output of such a device, the strength of which reaches 200–250 A);
output rectifier, assembled on the basis of power diodes (the task of this block of the inverter includes rectifying an alternating high-frequency current, which is necessary for performing welding).

Video (click to play).

The welding inverter circuit contains a number of other elements that improve its operation and functionality, but the main ones are the ones listed above.

Repair of an inverter-type welding machine has a number of features, which is explained by the complexity of the design of such a device. Any inverter, unlike other types of welding machines, is electronic, which requires specialists involved in its maintenance and repair to have at least basic radio engineering knowledge, as well as skills in handling various measuring instruments - a voltmeter, digital multimeter, oscilloscope, etc. ...

In the process of maintenance and repair, the elements that make up the welding inverter circuit are checked. This includes transistors, diodes, resistors, zener diodes, transformer and choke devices. The peculiarity of the design of the inverter is that very often during its repair it is impossible or very difficult to determine the failure of which particular element was the cause of the malfunction.

A sign of a burnt out resistor may be a small carbon deposit on the board, which is difficult to distinguish with an inexperienced eye.

In such situations, all the details are checked sequentially. To successfully solve such a problem, it is necessary not only to be able to use measuring instruments, but also to be quite familiar with electronic circuits.If you do not have such skills and knowledge at least at the initial level, then repairing a welding inverter with your own hands can lead to even more serious damage.

Realistically assessing their strengths, knowledge and experience and deciding to undertake independent repair of inverter-type equipment, it is important not only to watch a training video on this topic, but also to carefully study the instructions, in which manufacturers list the most typical malfunctions of welding inverters, as well as ways to eliminate them.

Situations that can cause the inverter to fail or lead to malfunctions can be divided into two main types:

associated with the wrong choice of welding mode;

caused by the failure of parts of the device or their incorrect operation.

The technique for detecting an inverter malfunction for subsequent repair is reduced to the sequential execution of technological operations, from the simplest to the most complex. The modes in which such checks are performed and what their essence is, is usually specified in the equipment instructions.Common inverter malfunctions, their causes and remediesIf the recommended actions did not lead to the desired results and the operation of the device has not been restored, most often this means that the cause of the malfunction should be looked for in the electronic circuit. The reasons for the failure of its blocks and individual elements may be different. Let's list the most common ones.

Moisture has penetrated into the interior of the device, which can happen if precipitation falls on the body of the device.

Dust has accumulated on the elements of the electronic circuit, which leads to a violation of their full cooling. The maximum amount of dust gets into inverters when they are used in highly dusty rooms or on construction sites. In order not to bring the equipment to such a state, its interior must be regularly cleaned.

Overheating of the elements of the electronic circuit of the inverter and, as a consequence, their failure can lead to non-observance of the duration of the switch (DC). This parameter, which must be strictly observed, is indicated in the technical passport of the equipment.

Liquid traces inside the inverter housingThe most common problems encountered when operating inverters are as follows.Unstable arc burning or active metal spatter This situation may indicate that the wrong amperage has been selected for welding. As you know, this parameter is selected depending on the type and diameter of the electrode, as well as on the speed of welding. If the packaging of the electrodes that you are using does not contain recommendations on the optimal value of the current strength, you can calculate it using a simple formula: 1 mm of the electrode diameter should account for 20–40 A of welding current. It should also be borne in mind that the lower the welding speed, the lower the current must be.Dependence of the diameter of the electrodes on the strength of the welding currentThis problem can be associated with a number of reasons, and most of them are based on undervoltage. Modern models of inverter devices also operate at reduced voltage, but when its value drops below the minimum value for which the equipment is designed, the electrode begins to stick. A drop in the voltage value at the output of the equipment can occur if the units of the device are poorly in contact with the panel sockets.This reason can be eliminated very simply: by cleaning the contact sockets and fixing the electronic boards in them more tightly.If the wire through which the inverter is connected to the mains has a cross section of less than 2.5 mm2, this can also lead to a voltage drop at the input of the device. This is guaranteed to happen even if such a wire is too long.If the length of the supply wire exceeds 40 meters, it is practically impossible to use an inverter for welding, which will be connected with its help. The voltage in the supply circuit can also drop if its contacts are burnt or oxidized. A frequent cause of electrode sticking is insufficiently high-quality preparation of the surfaces of the parts to be welded, which must be thoroughly cleaned not only from the existing contaminants, but also from the oxide film.Selection of the cross-section of the welding cableThis situation often occurs in the event of overheating of the inverter device. At the same time, the control indicator on the panel of the device should light up. If the glow of the latter is hardly noticeable, and the inverter does not have a sound alert function, then the welder may simply not be aware of overheating. This state of the welding inverter is also characteristic of a break or spontaneous disconnection of the welding wires.Spontaneous shutdown of the inverter during welding Most often, this situation occurs when the supply of the supply voltage is turned off by circuit breakers whose operating parameters are incorrectly selected. When working with an inverter device, automatic machines designed for a current of at least 25 A must be installed in the electrical panel.

If you know how to repair welding inverters with your own hands, then you can fix most of the problems yourself. Possession of information about other faults will prevent unreasonable costs for service maintenance.

Welding inverter machines provide high quality welding with minimum professional skills and maximum welder comfort. They have a more complex design than welding rectifiers and transformers and, accordingly, less reliable. Unlike the aforementioned predecessors, which are mostly electrical products, inverter devices are a rather complex electronic device.

Therefore, in the event of a failure of any component of this equipment, an integral part of diagnostics and repair will be checking the performance of diodes, transistors, zener diodes, resistors, and other elements of the inverter's electronic circuit. It is possible that you will need to be able to work not only with a voltmeter, digital multimeter, and other ordinary measuring equipment, but also with an oscilloscope.

The repair of inverter welding machines also differs in the following feature: there are often cases when it is impossible or difficult to determine the faulty element by the nature of the malfunction and you have to consistently check all the components of the circuit. From all of the above, it follows that for a successful self-repair, knowledge in electronics (at least at the initial, basic level) and little skills in working with electrical circuits are required. In the absence of these, do-it-yourself repairs can result in a waste of energy, time and even lead to additional malfunctions.

An instruction is included with each unit, which contains a complete list of possible malfunctions and the corresponding solutions to the problems that have arisen. Therefore, before doing anything, you should familiarize yourself with the recommendations of the manufacturer of the inverter.

All malfunctions of welding inverters of any type (household, professional, industrial) can be divided into the following groups:

caused by the wrong choice of the welding operating mode;

associated with the failure or malfunction of the electronic components of the device.

In any case, the welding process is difficult or impossible. Several factors can cause a problem with the machine. They should be identified sequentially, moving from a simple action (operation) to a more complex one. If all the recommended checks are completed, but normal operation of the welding machine has not been restored, then there is a high probability of a malfunction of the inverter module electrical circuit. The main reasons for the failure of an electronic circuit are:

Ingress of moisture into the device - most often occurs due to precipitation (snow, rain).
Dust accumulated inside the housing interferes with the normal cooling of the electronic components. As a rule, most of the dust gets into the machine when it is used on construction sites. To prevent this from causing damage to the inverter, it must be cleaned periodically.
Failure to comply with the manufacturer's mode of continuity of welding work can also lead to failure of the inverter electronics as a result of its overheating.

Most often, malfunctions are associated with external factors, settings and errors in the operation of the inverter. The most typical situations:

The welding arc is unstable or the work is accompanied by excessive spatter of the electrode material. This occurs when the wrong choice of current, which must correspond to the diameter and type of the electrode, as well as the welding speed. The manufacturer of the electrodes indicates recommendations for the selection of the current strength on the packaging. In the absence of such information, it is worth using the simplest formula: apply 20–40 A per 1 mm of the electrode diameter. If the welding speed is reduced, the current should be reduced.

The welding electrode sticks to metal - this can be caused by several reasons. Most often this happens due to a too low supply voltage of the network to which the device is connected, and in the case of an inverter with the ability to work at a reduced voltage, the latter is reduced when the load is connected to a level lower than the specified minimum. Another possible reason is poor contact of the device modules in the panel sockets. It is eliminated by tightening the fasteners or tighter fixing of the inserts (boards). A voltage drop at the input of the device can be caused by the use of a power strip, whose wire has a cross section of less than 2.5 mm 2, which also leads to a decrease in the supply voltage of the inverter during welding. Also, the reason may be too long an extension cord (with an extension wire length of more than 40 m, efficient operation is generally impossible due to very large losses in the supply circuit). Sticking can occur due to the burning or oxidation of contacts in the power supply circuit, which also leads to a significant "sagging" of the voltage. This problem can also manifest itself in the case of poor preparation of the products to be welded (the oxide film significantly worsens the contact of the part with the electrode).

The inverter is on, its indicators are on, but no welding. Most often this occurs due to overheating of the device, when the glow of the control indicator or lamp (if available) is hardly noticeable, and the inverter does not have a sound signal. The second reason is spontaneous disconnection of welding cables or their breakage (damage).

Turning off the mains voltage during welding - an incorrectly selected circuit breaker is installed in the electrical panel. This device must be rated for up to 25 A.

The inverter does not turn on - low voltage in the network, insufficient for the operation of the device.

Stopping the operation of the inverter during prolonged welding - most likely the temperature protection has tripped, which is not a malfunction. After a pause of 20-30 minutes, welding can be resumed.

Serious damage to the inverter module may be indicated by the smell of burning or smoke coming from the casing. In this case, it is better to seek help from service specialists. Do-it-yourself repair of welding inverters requires certain skills and knowledge.To identify and eliminate the cause of the malfunction, the body of the device is opened and its filling is visually inspected. Sometimes the whole point is only in poor-quality soldering of parts, wires, other contacts on the circuit boards, and it is enough to re-solder them to make the device work.At first, they try to identify damaged parts visually - they may be cracked, have a darkened case or pins burned out on the board, electrolytic capacitors will be swollen at the top. All identified faulty elements are soldered and replaced with the same or similar ones with suitable characteristics. The selection is made according to the markings on the case or according to tables. When soldering parts, the use of a soldering iron with suction will provide maximum speed and convenience of work. Image - DIY repair inverter welding machine

If the visual inspection did not bring any result, then proceed to ringing (testing) the parts using an ohmmeter or multimeter. The most vulnerable elements of inverter modules are transistors. Therefore, the repair of the apparatus usually begins with their inspection and verification. Power transistors rarely fail by themselves - as a rule, this is preceded by a failure of the elements of the "swinging" circuit (driver), the details of which are checked first. In the same way, by means of the tester, they call the rest of the board elements.

On the board, it is necessary to check the condition of all printed conductors for the absence of breaks and burns. The burnt areas are removed and the jumpers are soldered, as in the case of breaks, with a PEL wire (with a cross section corresponding to the board conductor). You should also check and, if necessary, clean (with a white eraser) the contacts of all connectors in the device.

Rectifiers (input and output), which are conventional diode bridges mounted on a heatsink, are considered to be quite reliable components of inverters. But sometimes they fail. It is most convenient to check the diode bridge after unsoldering the wires from it and removing it from the board. If the entire group of diodes rings for a short time, then you should look for a broken (faulty) diode.

The key management board is checked last. In the inverter module, this is the most complex element and the operation of all other components of the apparatus depends on its functioning. The final stage in the repair of the inverter welding device should be to check the presence of control signals coming to the busbars of the gates of the key block. Diagnose this signal using an oscilloscope.

In cases that are unclear and more complex than those described above, the intervention of specialists will be required. Trying to fix the malfunction yourself is not worth it, especially when the inverter is under warranty.

Inverter welding machines are gaining more and more popularity among master welders due to their compact size, low weight and reasonable prices. Like any other equipment, these devices can fail due to improper operation or due to design flaws. In some cases, the repair of inverter welding machines can be carried out independently by examining the inverter device, but there are breakdowns that are eliminated only at the service center.Welding inverters, depending on the models, operate both from a household electrical network (220 V) and from a three-phase (380 V). The only thing to consider when connecting the device to a household network is its power consumption. If it exceeds the capabilities of the wiring, then the unit will not work with a sagging network.So, the following main modules are included in the device of an inverter welding machine.Just like diodes, transistors are installed on radiators for better heat dissipation from them. To protect the transistor unit from voltage surges, an RC filter is installed in front of it.Below is a diagram that clearly shows the principle of operation of the welding inverter.So, the principle of operation of this module of the welding machine is as follows. The primary rectifier of the inverter is supplied with voltage from the household electrical network or from generators, gasoline or diesel.The incoming current is alternating, but passing through the diode block, becomes permanent... The rectified current is fed to the inverter, where it is converted back to alternating current, but with changed frequency characteristics, that is, it becomes high-frequency. Further, the high-frequency voltage is reduced by a transformer to 60-70 V with a simultaneous increase in the current strength. At the next stage, the current again enters the rectifier, where it is converted to DC, after which it is supplied to the output terminals of the unit. All current conversions controlled by a microprocessor control unit.Modern inverters, especially those based on the IGBT module, are quite demanding on the rules of operation. This is explained by the fact that when the unit is operating, its internal modules give off a lot of heat... Although both radiators and a fan are used to remove heat from power units and electronic boards, these measures are sometimes not enough, especially in inexpensive units. Therefore, you need to strictly follow the rules that are indicated in the instructions for the device, implying periodic shutdown of the installation for cooling.This rule is usually referred to as the “Duty Cycle” (Duty Cycle), which is measured as a percentage. Not observing the PV, overheating of the main units of the apparatus occurs and their failure occurs. If this happens with a new unit, then this breakdown is not subject to warranty repair.Also, if the inverter welding machine is working in dusty rooms, dust settles on its radiators and interferes with normal heat transfer, which inevitably leads to overheating and breakdown of electrical components. If it is impossible to get rid of the presence of dust in the air, it is required to open the inverter case more often and clean all the components of the device from accumulated dirt.But most often inverters fail when they work at low temperatures. Breakdowns occur due to the appearance of condensation on the heated control board, as a result of which a short circuit occurs between the parts of this electronic module.A distinctive feature of inverters is the presence of an electronic control board, therefore, only a qualified specialist can diagnose and eliminate a malfunction in this unit.... In addition, diode bridges, transistor blocks, transformers and other parts of the electrical circuit of the apparatus can fail. To carry out diagnostics with your own hands, you need to have certain knowledge and skills in working with measuring instruments such as an oscilloscope and a multimeter.From the above, it becomes clear that, without the necessary skills and knowledge, it is not recommended to start repairing the device, especially electronics. Otherwise, it can be completely disabled, and repairing the welding inverter will cost half the cost of a new unit.As already mentioned, inverters fail due to external factors affecting the “vital” units of the apparatus. Also, malfunctions of the welding inverter can occur due to improper operation of the equipment or errors in its settings. The most common malfunctions or interruptions in inverter operation are as follows.Very often, this breakdown is caused by faulty network cable apparatus. Therefore, first you need to remove the cover from the unit and ring each wire of the cable with a tester. But if everything is in order with the cable, then more serious diagnostics of the inverter will be required. Perhaps the problem lies in the standby power source of the device. The repair technique for the “duty room” using the example of a Resant brand inverter is shown in this video.This malfunction can be caused by an incorrect setting of the amperage for a certain diameter of the electrode.You should also consider and welding speed... The smaller it is, the lower the current value must be set on the control panel of the unit.In addition, to match the current strength to the diameter of the additive, you can use the table below.If the welding current is not regulated, the cause may be breakdown of the regulator or violation of the contacts of the wires connected to it. It is necessary to remove the cover of the unit and check the reliability of the connection of the conductors, and, if necessary, ring the regulator with a multimeter. If everything is in order with him, then this breakdown can be caused by a short circuit in the choke or a malfunction of the secondary transformer, which will need to be checked with a multimeter. If a malfunction is found in these modules, they must be replaced or rewound to a specialist.Excessive power consumption, even when the device is not loaded, most often causes turn-to-turn closure in one of the transformers. In this case, you will not be able to repair them yourself. It is necessary to take the transformer to the master for rewinding.This happens if the voltage drops in the network... To get rid of the sticking of the electrode to the parts to be welded, you will need to correctly select and set up the welding mode (according to the instructions for the device). Also, the voltage in the network may sag if the device is connected to an extension cord with a small wire cross-section (less than 2.5 mm 2).It is not uncommon for a voltage drop that causes the electrode to stick when using a power strip that is too long. In this case, the problem is solved by connecting the inverter to the generator.

Quite often, home craftsmen are faced with the need to perform welding. To do this, they need special welding equipment.

Today, welding inverters are a fairly common type of similar apparatus, which can increasingly be found among many owners. However, at a certain moment, this equipment may fail, which makes one think about repairs.

Moreover, in this case, it is not necessary to contact specialists; in some cases, you can return the welding machine to working condition on your own. The main thing is to know what exactly led to the malfunction and how you can eliminate it yourself without incurring unnecessary service costs.

One of the main qualities that ensured the popularity of inverter welding machines is high quality welding, which can be provided by any person who does not have sufficient skills in handling it. At the same time, the operating conditions of this unit themselves are distinguished by a high level of convenience.

It should be mentioned that this equipment has a more complex design when compared with welding rectifiers and transformers. This, in turn, negatively affects their reliability. It should also be said that the predecessors listed above are electrical devices. In contrast, inverter devices are one of the varieties of complex electronic devices.

For this reason, if the owner is faced with malfunctions in the operation of the welding inverter, in order to find the cause of the malfunction and carry out the repair itself, it is necessary to make sure that its constituent elements are working: diodes, transistors, zener diodes, resistors, as well as other elements of the inverter electronic circuit. You should also be prepared for the fact that the user will be faced with the need to use devices such as a voltmeter, digital multimeter, as well as other ordinary measuring equipment, including an oscilloscope.

When starting to repair inverter welding machines, you need to remember the following point: it is often difficult to understand, focusing only on the nature of the problem that has arisen, what exactly led to the termination of the operation of the machine.

In such a situation, the owner has no choice but to take turns check each element of the circuit... Therefore, in order for the repair to justify the efforts and time spent on it and to ensure the necessary result, the owner of such a device must have certain knowledge of electronics, as well as at least minimal skills in working with electrical circuits.

If he does not understand this plan, then, having decided on an independent repair of the inverter welding machine, he only risks wasting time in vain, without having achieved his goal. It is possible that his initiative may worsen the operation of the device, and the actions performed by him will cause new problems.

If we consider all the problems that are diagnosed during the operation of welding inverters of any type, then they can be classified into several groups:

malfunctions resulting from an illiterate choice of the welding operating mode;
malfunctions caused by a malfunction or improper operation of the electronic components of the equipment.

Regardless of the nature of the malfunction, such a situation will not allow the owner to continue welding in the usual mode. Various factors can cause a malfunction in the operation of the welding inverter. To determine the exact cause, it is necessary to check each of them in turn, and at the beginning they start with simple operations and gradually move on to more complex ones. After carrying out all the recommended diagnostic procedures, it may happen that the welding machine is still inoperative. In this case, it can be assumed that the problem is related to the inoperative electrical circuit of the inverter module. The most common failure of an electronic circuit occurs for the following reasons:

Penetration of moisture into the device. In most cases, precipitation contributes to this.
In the event of dust accumulation under the housing, favorable conditions arise for disrupting the correct cooling of the components of the electronic circuit. Equipment used on construction sites is most often at greatest risk of contamination. To prevent damage to the inverter under these operating conditions, clean it regularly.
Disregard of the manufacturer's recommendations regarding the proper use of the inverter without interruption. This can also be one of the causes of malfunctions in the operation of the electronics of the equipment, arising against the background of its overheating.

Usually, inverter devices fail due to external factors, as well as incorrect settings and neglect of the recommendations for using the device. Among such situations, the following can most often be observed:

A burning odor from the cabinet of the unit may be a sign of a serious problem with the inverter module. In such a situation, the best solution would be service call... To fix such a malfunction with your own hands, the owner must have certain skills and knowledge.

The do-it-yourself repair procedure consists in gaining access to the body of the device, further examining its filling. In some cases, the cause of the malfunction may be poor soldering of elements, cables, and other contacts on the circuit boards.

Therefore, in such a situation, return the device to working condition. can be by soldering... At the initial stage, you need to try to find out which elements are out of order. This may be indicated by cracks, dark spots on the case, or signs of burnout on the terminal board, as well as swelling of the top of the electrolytic capacitors.

After it was possible to establish the faulty nodes, they must be evaporated, then replaced with parts identical or similar to them in terms of characteristics. When choosing replacement parts, pay attention to the markings on the body, or use tables. When removing damaged elements, it is recommended to use a soldering iron with suction. This will allow you to complete the work with a minimum amount of time and avoid serious problems.

In some cases, the survey may not produce results. In a situation like this, it makes sense to start ring out elementsusing an ohmmeter or multimeter. Transistors have the lowest level of protection. For this reason, during the repair of the device, it is necessary first of all to examine them and check their operability. Most power transistors are highly reliable. And if, nevertheless, they turned out to be faulty, then the most often favorable factor for this is the failure of the elements of the "swinging" their circuit. The elements of the latter must be checked at the very beginning. After completing the check, it is necessary to subject the nickname and other elements of the board.

When examining the board, attention should be paid to the state each printed conductorwhere you need to make sure that they do not have breaks and burns. If burnt areas were found, they must be removed and the jumpers soldered. This operation is performed by hand in the same way as in the case of damage to the PEL cable. If necessary, then the contacts of each of the connectors present in the device should also be checked. In some cases, they will need to be cleaned.

Inverter welding machines can greatly simplify the welding procedure for various products. The failure of this equipment can upset any owner. However, you should not contact the service center specialists ahead of time. In some cases, you can return the device to a working condition with your own hands. Often this equipment has quite simple faultsthat can be easily eliminated. The main thing is to clearly understand what exactly led to the failure of the device and how to properly repair it.

Video (click to play).