The most complex element of the inverter is the key control board, the health of which depends on the performance of the entire device. Such a board for the presence of control signals that are fed to the gate buses of the key block is checked using an oscilloscope. The final step in testing and repairing the electronic circuits of the inverter device should be to check the contacts of all existing connectors and clean them with a regular eraser.
Self-repair of an electronic device such as an inverter is quite difficult. It is almost impossible to learn how to repair this equipment just by watching a training video, for this you need to have certain knowledge and skills. If you have such knowledge and skills, then watching such a video will give you the opportunity to make up for the lack of experience.
VIDEO 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.
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If the indicator is on, this indicates overheating of the main modules of the unit. Also, the device can turn off spontaneously, which indicates tripping of thermal protection ... So that these interruptions in the operation of the unit do not occur in the future, again, it is necessary to adhere to the correct mode of the duration of the on (DC). For example, if duty cycle = 70%, then the device should work in the following mode: after 7 minutes of operation, the unit will have 3 minutes to cool down.
In fact, there can be a lot of various breakdowns and the reasons that cause them, and it is difficult to list them all. Therefore, it is better to immediately understand what algorithm is used to diagnose the welding inverter in search of faults. You can find out how the device is diagnosed by watching the following training video.
The design of a welding inverter is rather complex, therefore, the least safe to operate. The great advantage is the high quality of the work performed by the device. At the same time, any structure wears out and breaks down over time. Therefore, there are two solutions to this problem. In the first case, the apparatus is repaired by hand, and the second case is associated with contacting specialists for the repair of welding inverters.
Diagram of a welding inverter semiautomatic device.
A complex device requires appropriate knowledge and the correct approach to repair. It is important to understand electronics here, that is, diodes, transistors, resistors and stabilizers.
What devices will be needed for this:
Multimeter connection diagram.
Other special instruments will be required to measure various indicators. It can be too difficult to detect a malfunction, therefore, it will be necessary to check all the elements more than once, their certain sequence, in which they should be contained in the general scheme.
The operation of the inverter is based on a scheme associated with a step-by-step signal conversion. Initially, the current is rectified due to the input rectifier, after which it begins to be converted into variable frequency current due to the inverter module. Then, a power transformer is involved in the conversion process, therefore, the frequency current is converted into a welding one. After the transformer, the variable frequency current is converted into a welding form due to the output rectifier. Before inspecting the inverter, refer to its microcircuit and drawings.
It is necessary to emphasize that the main features of welding inverters is the accuracy of work. If even the highest quality inverter is out of order, then among the main reasons for this are the following:
Incorrect use of the device.
Lack of accurate connection of the device.
Changes in mains voltage.
Changes in current strength.
Figure 1. List of possible malfunctions of the welding inverter.
The causes of breakdowns can also be bad weather conditions, if they are observed during the operation of the device on the street. These may be too dirty rooms, high levels of humidity, rain, snow, etc. The most vulnerable point of the inverter is the terminal block, the cable is connected to it. The lack of normal contact and at the same time a significant indicator of the current strength will be a prerequisite associated with overheating of all elements and connections.
Melting of the insulation is also a malfunction, which can cause a short circuit. The list of possible malfunctions is presented in the table (Fig. 1).At the same time, do-it-yourself repair of the welding inverter is carried out by stripping the contacts and tightly joining the connection, which heats up during operation.
There are the following main stages associated with the diagnosis of inverter malfunctions:
The equipment does not turn on.
The inverter shuts down by itself.
The appliance makes a lot of noise.
Strong overheating of the structure occurs.
An interruption of the electric arc is observed during welding.
Poor current regulation.
Electricity consumption is over-limit.
If the device does not turn on, then the main reason for this is:
Lack of mains voltage.
Operation of the machine on the dashboard.
The equipment stops working.
Before starting the repair of the inverter for welding with their own hands, they check the transistors, which often fail in the first place.
Diagram of an electronic oscilloscope device.
A thorough inspection will be required here. The appearance of the faulty part speaks for itself, featuring a warped body. If a burned-out transistor is found, it must be replaced with a new one. If there are no external defects, then with the help of a multimeter it is necessary to ring the transistor, after which you should select a new element and make it a high-quality installation in place of the previous transistor.
Power transistors have driver elements that should be checked second. This type of parts is more resistant to damage, since this can happen to the elements that power the drivers themselves. An ohmmeter allows you to check the performance of the power transistors, after which the part can be evaporated and replaced with an analog.
If there are difficulties in detecting defects, then it is very important to check the rectifiers connected by diode bridges mounted on the basis of a radiator. These elements of the inverter have significant durability, as breakdown inside the mechanism can occur. Diagnostics of the diode bridge requires first to release it from any wires with a soldering iron, removing it from the control board, respectively. The work with the inverter is greatly facilitated by the lack of dependence of the circuit on a short circuit. A soldering iron equipped with a suction helps to evaporate the faulty diode.
Finishing the diagnostics, they inspect the board that allows you to manage the keys. This detail is a complex and important element of the apparatus. Finishing the repair of the inverter, they check the operation of the control signals, which should go to the busbars of the gates of the key module.
Diagram of the front panel of the inverter.
Monitoring this control signal is not difficult as an oscilloscope can be used. If the case is unclear, expert intervention will be required.
Long and trouble-free operation of the inverter can be ensured by observing special rules:
Carrying out a technical inspection of the welding inverter before starting work with it and preparing the workplace.
Installation of the device in a horizontal position, which will prepare the workplace.
Connecting welding cables to the power connectors of the device: to the electrode holder with a "+" sign, and to ground - with a "-" sign.
Checking the fixation of the cable glands in the soldering sockets by turning them clockwise.
Connect the appliance to the power supply by plugging it into a power outlet.
Switch the switch to the "ON" position to turn on the fan.
Trial arc ignition.
The current regulator knob sets the required mode for welding.
If you follow the recommendations related to the correct maintenance of the device, then it will serve for a long time:
Block diagram of a digital voltmeter with a time-to-pulse converter.
It is strictly forbidden to use the device with the cover removed for a long time.
Inspection of the internal components of the device should be carried out more often, which is determined by the frequency of use of the device and the degree of contamination of the working space.
The dust accumulated in the device must be removed by using compressed air at low pressure, i.e. less than 10 bar.
Cleaning of electronic boards is not done with a jet of compressed air, but only with a small brush.
Before carrying out work, a safety check should be carried out when fixing the power connectors in the corresponding sockets of the device, check the power plug, socket and the insulation of the electronic cable.
Transport and storage of the device must be suitable for weather conditions.
When transporting the device by transport, it can also be placed in an upright position.
Store the device only in a dry room where the relative humidity is 80%.
The inverter is kept disconnected from the mains.
Welding inverter circuit.
To repair a faulty inverter, you should find out all the principles of its operation. At the first stage of work with the welding inverter, the mains voltage is rectified by the devices, and then it is converted into a variable frequency voltage. After that, it is reduced to a level that allows safe welding. The last stage is associated with the presence of constant welding voltage.
The listed processes are regulated by the control unit, which has a rather complex design. Starting the repair of the welding inverter, it must be visually inspected in order to clean out all the places that do not have normal contact.
These zones are traditionally rectifier diodes. It is possible to mount the diodes using threaded connections, and all special tools are not needed.
Pre-check the diodes, examining their "throughput" or "breakdown", which is associated with the possibility of free passage of current through the diode in the same direction. This is done with a multimeter. With a constant resistance, in the case of measurements from plus to minus, the diode should be replaced.
VIDEO Even a faulty diode will allow welding with an inverter, and the ability to turn on the device is not associated with ensuring normal operation. If the device cannot be turned on or off normally, an urgent repair will be required. Any inverter model has a fuse on the control board. If you dismantle it, then you can get to this device.
Removing the control board requires marking all connectors, of which there can be more than three, and they themselves are similar to each other. If the fuse is defective, then it is not difficult to assemble and install it, only patience and accuracy are required.
Welding inverter power circuit.
Often the reason for the failure of the transistors of welding inverters is insufficient cooling. The element contact must have thermal grease and a heat sink plate. It is not difficult to unsolder and install the part, but it is imperative to control the possibility of its overheating, since a sufficiently hard-melting solder is used for soldering.
If the power transistor fails, then this leads to breakdown of the drivers adjacent to this part. Diodes and zener diodes can often fail. The transistors are first inspected from the outside and then replaced.
If the transistors have already been inspected and checked, followed by replacement, since the cause of their breakdown has been found, then the presence of a "swinging" driver is considered as a prerequisite. Similarly, using the tester, you can call any elements of the board, replacing them with serviceable ones.
It is imperative to check the printed conductors of the board, which will reveal the presence of burn. Existing burnt-on areas can be removed and the other jumpers can be re-soldered.All soldering points are covered with a special varnish. First, check and clean each pin of the connectors with a white drawing eraser.
Diagram of the internal device of the welding inverter.
Rectifiers are output and input full-wave diode bridges that are equipped with silicon valves. They are considered reliable parts, but they can also wear out. Controlling them is not a difficult task. Soldering bridges from electronic circuits is associated with dismantling the brackets. If the bridge is ringing only in one of the directions, then it is serviceable, and if in both directions at once, then this bridge is broken. The check is carried out when the bridge is already assembled and in place.
Checking the board that allows the control of the device is associated with a continuity tester, which allows you to control the gate control signal using the key module. You can check it using an instrument called an oscilloscope. In a normal test, all signals will be correct, otherwise it will turn out that something has been missed.
VIDEO If a semiautomatic welding machine is used, then only mechanical malfunctions can occur in it. For example, if a delay in wire feeding is detected, then this may occur for the following two reasons:
The wire feeder has a low clamping force that needs to be adjusted correctly.
A strong process of friction is observed between the wire and the channel in the sleeve.
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Change the channel in one pull. For this purpose, the old one is removed and a new channel is placed, allowing to unite the beginning and the end.
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.
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.
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:
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.
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 elements using 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 conductor where 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 faults that 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).
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