Features of operation and possible malfunctions of welding inverters. Various malfunctions of welding inverters Features of operation and possible malfunctions of welding inverters

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, repair of inverter welding machines you can do it yourself by examining the device of the inverter, but there are breakdowns that are fixed only in a 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 possibilities of electrical wiring, then the unit will not work with a sagging network.

So, the device of the inverter welding machine includes the following main modules.

How an inverter works

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 receives voltage from the household electrical network or from generators, gasoline or diesel. The incoming current is variable, but passing through the diode block, becomes permanent. The rectified current is fed to the inverter, where it is inversely converted 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 current strength. At the next stage, the current again enters the rectifier, where it is converted to direct current, after which it is fed to the output terminals of the unit. All current conversion controlled by a microprocessor control unit.

Causes of breakdowns of inverters

Modern inverters, especially those made on the basis of an IGBT module, are quite demanding on the operating rules. This is explained by the fact that during the operation of the unit, its internal modules give off a lot of heat. Although both heatsinks 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, it is necessary to strictly follow the rules that are indicated in the instructions for the device, which imply periodic shutdown of the unit for cooling.

This rule is usually referred to as “Duration On” (DU), which is measured as a percentage. Not observing the PV, the main components of the apparatus overheat and fail. If this happens with a new unit, then this failure is not subject to warranty repair.

Also, if the inverter welding machine is running 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 necessary to open the inverter case more often and clean all the components of the device from accumulated contaminants.

But more often than not, inverters fail when they work at low temperatures. Breakdowns occur due to the appearance of condensate on a heated control board, resulting in a short circuit between the parts of this electronic module.

Repair features

A distinctive feature of inverters is the presence electronic board control, therefore, only a qualified specialist can diagnose and eliminate a malfunction in this unit. In addition, diode bridges, transistor blocks, transformers and other parts can fail. electrical circuit device. To carry out diagnostics with your own hands, you need to have certain knowledge and skills in working with such measuring instruments like an oscilloscope and a multimeter.

From the foregoing, 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 the repair of the welding inverter will cost half the cost of a new unit.

The main malfunctions of the unit and their diagnostics

As already mentioned, inverters fail due to the impact on the “vital” blocks of the apparatus external factors. Also, malfunctions of the welding inverter can occur due to improper operation of the equipment or errors in its settings. The following malfunctions or interruptions in the operation of inverters are most often encountered.

The device does not turn on

Very often this failure is caused malfunction network cable device. Therefore, you first need to remove the casing from the unit and ring each cable wire 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 supply of the device. The technique for repairing the "duty room" using the example of a Resant brand inverter is shown in this video.

Welding arc instability or metal spatter

This error may be caused incorrect setting current strength for a certain electrode diameter.

Advice! If there are no recommended current values ​​on the package for the electrodes, then it can be calculated using the following formula: for each millimeter of equipment there should be welding current within 20-40 A.

It should also be taken into account welding speed. The smaller it is, the lower the current value must be set on the control panel of the unit. In addition, in order for the current strength to correspond to the diameter of the additive, you can use the table below.

Welding current not adjustable

If the welding current is not adjusted, the cause may be regulator failure or violation of the contacts of the wires connected to it. It is necessary to remove the casing 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 it, then this breakdown can be caused by a short circuit in the inductor 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 by a specialist.

Large power consumption

Excessive power consumption, even when the machine is unloaded, causes, most often, interturn short circuit 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.

The electrode sticks to the metal

This happens if network voltage drops. To get rid of the electrode sticking to the parts to be welded, you will need to correctly select and adjust the welding mode (according to the instructions for the machine). Also, the voltage in the network may sag if the device is connected to an extension cord with a small wire section (less than 2.5 mm 2).

It is not uncommon for a voltage drop causing sticking of the electrode to occur when using an extension cord that is too long. In this case, the problem is solved by connecting the inverter to the generator.

Burning overheat

If the indicator is on, this indicates overheating of the main modules of the unit. Also, the device may spontaneously turn off, which indicates thermal protection trip. So that these interruptions in the operation of the unit do not happen in the future, again, you need to adhere to correct mode duration of inclusion (PV). For example, if PV = 70%, then the device must operate in the following mode: after 7 minutes of operation, the unit will be given 3 minutes to cool down.

In fact, various breakdowns and there can be quite a lot of reasons causing 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 looking at the following tutorial.

When buying an inverter welding machine to work in a garage or in the country, the first thought is wow, now I’ll cook everything! No welder's diploma required, the device is designed for the user without special education. Handling welding has become easier and more comfortable. The main thing is to understand the principle of operation and first aid in case of difficulties and breakdowns.

Inverter devices - a new generation of manual welding

Since the early 2000s, inverter welders have become cheaper and more affordable. To spend at home welding work, it is enough to have this small and easy-to-handle device and good electrodes.

Benefits of inverters

Inverter devices are light in weight, compact in size, and their scope and welding quality are higher than those of heavy and bulky welding transformers. They fulfill their task in full: they cook cars, gates, pipe structures (for example, greenhouses or gazebos). Working with them is mobile - throwing a sliding belt over the shoulder, welding is carried out in any hard-to-reach places.

With vertical, horizontal or top welding, the current is reduced by 10–20%, and when welding at an angle, it is increased by the same amount compared to the usual position.

There are also no problems with the connection, the welding machine runs on a conventional electrical network. It is great that it will not stop when the mains voltage drops. If the deviation is within +/- 15%, the device will continue to operate normally. The current value can be adjusted by selecting the power depending on the type and thickness of the metal. All this makes inverters ideal for both beginners and professionals.

Video: testing a homemade inverter apparatus

How Welding Inverters Work

The inverter unit connects the parts direct current using arc welding with a coated electrode. A big plus is that at the very beginning of the process there are no power surges in the network to which the device is connected. Storage capacitor ensures continuity electrical circuit and soft ignition of the arc with its further automatic maintenance. When connected to an electrical outlet, the alternating mains voltage with a frequency of 50 Hz is converted first into a constant, and then into a high-frequency modulated voltage. Then, using a high-frequency transformer, the current increases, the voltage decreases, and the output current is rectified. The device provides adjustment of size of welding current and protection against an overheat.

The inverter device first rectifies and modulates the input current, and then increases its strength by reducing the voltage until the arc appears

The basic mode of operation of inverter welding machines is MMA. This is manual arc welding with piece coated electrodes. For welding steel and cast iron products permanent or alternating current use a diameter of 1.6–5.0 mm.

Devices differ in power and duration of the working cycle. The second indicator is the period during which it is allowed to cook at the maximum allowable power in order to prevent the device from overheating. It is denoted by the letters PV (on period) and is determined as a percentage relative to a time unit of 10 minutes. For example, if the appliance says 60% PV, this means that it can be boiled for 6 minutes and then turned off for 4 minutes. Sometimes the welding cycle is set to 5 minutes. Then the value of the PV indicator of 60% means a period of work of 3, and a rest of 2 minutes. The PV and duty cycle indicators are indicated in the instructions for each device.

The device of the welding machine

In order not to look for a repair specialist at the first difficulties in the operation of the device, it is advisable to have at least a basic idea of ​​\u200b\u200bits design.

Do-it-yourself inverter assembly scheme

Masters with knowledge of electrical engineering assemble the welding machine themselves. Not only for the sake of economy, but also at the behest creative soul. Schematic diagrams of inverters, drawings and instructions of those who made the inverter themselves are posted on the Internet. The main thing is to get stability welding arc. Most often, the “oblique bridge” circuit (“Barmaley circuit”) is used using two key transistors: bipolar or field-effect. They are placed on a radiator to remove heat, they open and close synchronously.

In the “Barmaley circuit”, the main control elements are two transistors that open and close synchronously

The electrical solution of the circuit eliminates high-voltage surges and allows the use of relatively low-level switches. The scheme is used because of its simplicity, reliability and not very expensive consumables.

Video: an overview of the Barmaley scheme

Do-it-yourself inverter assembly

The apparatus is assembled from the following blocks:

• power supply for stabilizing input signals. A metal partition is placed between it and other elements and blocks. The multi-winding choke is controlled by transistors and a stored energy capacitor. Diodes are used in the throttle control system;
• a power unit, with the participation of which a full cycle of current conversion takes place. They are assembled from a primary rectifier, an inverter transistor converter, a step-down high-frequency transformer and an output rectifier;
• Control block. It is based on a master oscillator with a special microcircuit or a pulse-width modulator. They put a resonant choke and 6-10 resonant capacitors;
• protective block. More often they are assembled on a power unit, installing thermal switches for thermal protection of its elements. To avoid overloads, they put a board based on the 561LA7 chip. Snubbers with resistors and capacitors K78-2 protect the converter and rectifiers.

Video: welding inverter assembly

Causes of failure of inverters

The design of inverter welding machines is more complicated than transformer ones and, unfortunately, less reliable. This often leads to failure of various nodes for the following reasons:

• low protection against dust. When it accumulates inside, a thermal protection signal is triggered, the device turns off. Need dismantling at least twice a year to clean the internal parts with a jet compressed air or soft brush;
• moisture getting inside, causing a short circuit, dangerous for the unit;
• low quality of the cooling system in cheap devices. Because of this, the plastic parts of the structure melt, and the emergency shutdown does not work. In models with tunnel ventilation, the radiator is located along the body, and the main components are inside it. Such devices are much more expensive;
• power surges, especially drops to 190 V or more;
• overload when cutting thick metal and work for which a particular machine is not designed. Then the IGBT power module fails;
• poor-quality fastening in the contacts of the pads, which provokes overheating of these places and sparking;
• sensitivity to shocks and falls due to the presence of plastic parts;
• low quality of spare parts that are used in repairs;
• temperature violation. Electronic microprocessors melt and break when overheated. It is recommended to adhere to the range from -10 to +40 o C.

Frequent breakdowns of welding inverters

Malfunctions can be both mechanical and related to the failure of electronics. Welding machine - complex device, problems can occur anywhere:

Short circuit or breakage in any important node wiring diagram makes it impossible to operate the welding machine:

• a malfunction of the control board does not give a stable welding current and does not allow a normal arc to be obtained;
• damage to the transistor of the upper printed circuit board leads to the shutdown of the device;
• failure of the overheating protection system is determined by the smell of burnt insulation, smoke comes from inside the case.

Repair methods for inverter welding machines

When starting to repair a faulty unit, it is worth considering some points.

What is fixed without opening

The poor quality of the device does not always mean an internal breakdown. Wet or poor quality electrodes are often the culprit. If drying or replacing does not give a beautiful seam, consider other possible reasons:

• poor ignition, sticking of electrodes to metal is often due to power loss in work cables or low welding current. Correct selection cable sizing and increased amperage can alleviate the problem. Do not use power extension cords with a wire cross section of less than 2.5 mm2 and great length. Optimal length up to 15 m, maximum - 40 m, otherwise the device will not work due to current loss. Welding cable is recommended up to 5 m long;

  To connect the welding machine, you must use an extension cord with a wire section of at least 2.5 square meters. mm and length no more than 40 m

• interruption, arc pulsation causes instability or low value of the welding current. Check the reliability of the connections or increase the current. If there are significant power surges in the network, use a stabilizer;
• strong spatter of metal provokes a high welding current or incorrectly set polarity. Decrease the current strength and observe the polarity;
• humpbacked, with undercuts, the seam is corrected by increasing the current and correct installation polarity;
• porous seam with large quantity defects are obtained due to unprepared metal or long arc welding. The number of weld defects can be reduced by cleaning the rusty and dirty surface and bringing the electrode closer to the metal.

  Defects weld occur due to insufficient cleaning of the surfaces to be treated, incorrect polarity or too much removal of the electrode from the welding site

It is important to choose the right electrode size for the correct operation of the welding machine.

Table: Correspondence of the diameter of the electrodes with the thickness of the metal

Internal organization

To be able to repair the welding machine yourself, you first need to deal with its internal structure. On the front panel there are sockets for working cables, a current regulator knob and an on indicator. If the design provides for additional functions, working indicators are located here.

On the front panel of the welding machine there are sockets for connecting cables, a knob for adjusting the current intensity and an operating mode indicator

The test begins with an external inspection of the device. First, check for the presence mechanical damage. If there are black spots on the case, most likely a short circuit has occurred. The tester checks the fuses, replace them if necessary, examine the insulation of the welding cables, the connections in the sockets. If necessary, tighten the bolts, clean the contacts.

After unscrewing the screws and removing the casing, the inner part machine containing the following components:

• board with power transistors;
• control board;
• rectifier diode board;
• mains voltage rectification board;
• fan;
• controls - handle and switches.

Tools for the job

Repair will require the following tools .

Do-it-yourself welding machine repair

The filling of the welding machine is clear to those who work with radio electronics. If the necessary skills in this area are not available, intervention will only hurt. Without knowing the rules for handling the board and the technology of such fine work, it is possible to cause damage much greater than the initial one. It is cheaper and safer to entrust repairs to a professional.

If it is difficult to find a specialized workshop, you have to restore the welding inverter yourself. Important sequentially check what stopped the device.

If you encounter difficulties, read the operating instructions for the welding machine first. It must have a section on possible problems when welding, the causes of malfunctions and recommendations for their elimination.

After removing the cover of the device, there is often a noticeable violation of the soldering of parts, swelling of capacitors, and broken contacts. In such cases, damaged parts are replaced with similar ones. Torn off and burnt areas are removed and soldered again. If it is not possible to quickly determine the cause of the breakdown, check each element of the electrical circuit. Test diodes, transistors, zener diodes, resistors and other details.

A detailed check is carried out sequentially: from the parts that most often fail to the most resistant.

1. Power diodes. For their continuity, the tester is switched to diode mode, the probes touch the output terminals. If there is ringing in one direction, but not in the other, the power diodes are in order, the lower module of the device is working.

   If the input terminals ring only in one direction, then the power diodes are working.

2. Power transistors. Power transistors are the most vulnerable parts in an inverter. Keep in mind that when transistors are arranged in blocks, due to one faulty, the entire arm does not work. Check them in the following order:
   
3. Button contact. It is checked in ringing mode by putting the button in the “on” position. If the contacts are ringing, the button works.

   The button is checked in the “on” mode by calling its contacts

4. network bridges. These are reliable elements, but they also sometimes fail. Before checking, it is better to unsolder the wires from them and remove the board. In ringing mode, the black probe is placed on the positive terminal of the diode, and each terminal of the network bridge is touched in turn with red. Then vice versa - red is put on the negative terminal of the diode, black on each output of the network bridge. If the tester shows numbers everywhere, short circuit no, the diode bridges are fine.

   The diode bridge is tested by touching each of its terminals in turn.

5. Field effect transistor in the primary power supply. It is checked according to the scheme described in the second paragraph. If there is a charge, the power supply is good.

   The field effect transistor in the primary power supply is called in the same sequence as the power transistors

6. Power nodes. If there is no oscilloscope, use a tester that is put into voltage test mode. The device is connected to the network through a light bulb. If there is voltage at the output, the lamp will light up, i.e. the nodes are working.

   If the lamp connected in series with the device lights up, the power units are working

7. charging resistor. cliff charger possible if the lamp does not light up when the device is turned on. They check the serial chain of the PTC and NTC, which provides the charge of the capacitor. The resistance breaks when the diode bridges or power transistors are short-circuited.

   To check the charging resistor, check the serial chain of the PTC and NTC

8. Key management board. This is a complex element of the inverter, on the functioning of which the operation of the entire device depends. They check the switched on device in voltage mode up to 20 V. The regulator is set to the minimum position, the black probe is installed on the terminal, the red probe is on the sixth output. When the regulator is turned to the maximum position, the tester shows a change in voltage. If on devices 160-200 A the change is in the range of 2.4-3.2 V, the regulator circuit is in order.

   Testing of the key management board is carried out by a tester with the device turned on in voltage mode up to 20 V

9. cliff feedback. The device is turned on, the voltage is set on the tester in the range of 20 V. The black probe is placed on the terminal, the red one on the second output. A 200 A device will display a voltage of 14-50 mV. If there is an open shunt feedback, the tester will read about 500 mV. So there is no feedback anywhere.
   

   When looking for a break in the feedback, the red probe is installed on the second output of the microcircuit

10. Power Supply. In the “on” mode, the presence of a voltage of 300 V from the capacitor to the inverter board is checked. Check the integrity of the circuit and the transistor. At the output of the power supply, two diodes provide 25 V. If the ringing showed that there is no short circuit, the secondary circuits do not load the power supply, it will start. If there is no start, the optocoupler or transistor may be broken. If the power supply starts up for a short time and then disconnects from the mains, check the transistor. If it warms up, it means that the diode is broken nearby and needs to be replaced.
    

    Before checking the power supply, unplug the device!

    At the first stage of the repair of the power supply, the presence of a voltage of 300 V is checked on the inverter board.

When self-repairing, craftsmen use phosphoric acid. If you need to solder something to the diode cases (for example, broken racks), they are pre-tinned. When repairing a broken rack, perpendicularity is taken into account. It is important to install it, clearly combining the holes. If soldered even with minimal distortion, the subsequent tightening of the mount will break the rack again.

If not technical hair dryer, for soldering use a soldering iron 100-150 watts. So the connectors and tracks will not be damaged. Experts recommend for best result before soldering, heat the block to 160–170 0 C, while the plastic parts of the fan cannot be heated. When working with a soldering iron or other heating elements Care must be taken not to touch the fusible parts of the apparatus.

Video: repair of the welding machine and analysis of its main malfunctions

The inverter welding machine is confidently prescribed in home workshops. Before buying, you should spend time learning the basics of welding and electrical engineering. This will help you navigate the characteristics of the device and, if necessary, repair it yourself. Difficult cases it is better to entrust the experts.

The welding inverter is modern equipment, the use of which in the welding process makes it possible to achieve very High Quality work and gives the welder the opportunity to work in comfortable conditions. But at the same time, the welding inverter also has a more complex design compared to previous models of welding equipment, which increases the chance of a malfunction during its operation.

As a rule, all malfunctions of the welding inverter can be divided into two groups:

• malfunctions associated with incorrect operation of the electronic "stuffing" of the device

• malfunctions associated with wrong choice operating mode.

The second type of malfunction occurs most often, therefore, before contacting a specialized workshop or starting to disassemble the device on your own in order to identify a breakdown, you need to check whether all the settings for the operating mode are set correctly, and in addition, you should read the operating instructions for this device again, to determine if you are making any mistakes in the process. Most manufacturers, when compiling instructions, indicate the causes of malfunctions of the welding inverter that may occur during operation, and also describe how these malfunctions can be eliminated on their own.

Causes of breakdowns of welding inverters and options for their elimination.

There are a number of typical faults that occur when we are talking about welding inverters:

• instability of the welding arc and strong spattering of the metal;
• sticking welding electrode;
• lack of welding process when the machine is turned on;
• lack of reaction of the device when it is turned on.

Let us consider in more detail why this or that situation may arise, and what can be done in the event of any malfunction of the welding inverters.

• Welding arc instability and strong metal spatter.

This malfunction may occur if you incorrectly selected the current during welding. As a rule, the welding current is selected in accordance with the type and size of the electrode used in welding. But there is one more thing to remember here. important rule: the selected current must also correspond to the speed at which welding is carried out. If the welding speed decreases during operation, then the welding current must also be reduced.

• Sticking welding electrode.

There can actually be several reasons for this type of malfunction. It is possible that during welding, the voltage unexpectedly decreased in the network, which led to a strong sticking of the welding electrode. It can also “stick” even if the inverter is connected to the network with a cable with a too small cross section. Another reason for this "behavior" of the electrode may be poor contact of the electrode with the surface to be welded due to the fact that the surface has undergone oxidation due to exposure to atmospheric oxygen. In this case, welding must be stopped, and the surface of the part must be cleaned from the film.

• Lack of welding process when the machine is turned on.

In the vast majority of cases, this behavior of the welding inverter can be explained by the absence of mass on the surface of the part to be welded. In addition, it would be useful to check the condition of the welding cable - it may be damaged. This situation is quite common in the event that the part being welded has a large weight, as a result of which the fall of the part on the wire can violate its integrity.

• No reaction of the device when turned on.

If nothing happens when the welding inverter is turned on, then the cause of such a malfunction should be sought, in many cases, not in the inverter itself, but in the electrical network to which it is connected. The mains voltage may be too low and therefore the machine cannot work. Another reason that the device does not turn on may be an incorrectly selected circuit breaker installed in the shield. A weak switch is able to trip when the inverter is turned on. In addition, turning off the device can lead to the fact that the electricity will disappear throughout the house.

In addition to these malfunctions, there are also interruptions in the operation of the welding inverter, which are not associated with a breakdown of the device, but are the result of a fairly high-quality and timely operation of the protection systems that the inverter is equipped with. So, for example, for a long continuous work the inverter may trip spontaneously. This happens if the device overheats and the temperature protection trips. In this case, you should stop the welding process for about 20-30 minutes, let the machine cool down, after which work can be continued.

It is well known that the repair of welding machines in the vast majority of cases can be organized and carried out independently. The only exception is the restoration of the electronic inverter, the complexity of the circuit of which does not allow for a full repair at home.

Just one attempt to disable the inverter protection can confuse even an electrical engineer. So in this case, it is best to seek help from a specialized workshop.

The main manifestations of malfunctions of electric arc welding machines are:

• the device does not turn on when connected to the mains and starting;
• sticking of the electrode with a simultaneous hum in the area of ​​​​the converter;
• spontaneous shutdown of the welding machine in case of overheating.

Repair always begins with an inspection of the welding machine, checking the supply voltage. It is not difficult to repair transformer welding machines, moreover, they are picky in maintenance. For inverter devices, it is more difficult to determine a breakdown, and repairs at home are often impossible.

However, with proper handling, inverters last a long time and do not break. It must be protected from dust, high humidity, frost, and stored in a dry place. There are the most typical malfunctions of welding machines, which you can fix with your own hands.

Device won't start

In this case, first of all, you need to make sure that there is voltage in the network and the integrity of the fuses installed in the transformer windings. If they are in good condition, use the tester to ring the current windings and each of the rectifier diodes, thereby checking their performance.

If one of the current windings breaks, it will need to be rewound, and in the event of a malfunction of both, it is easier to replace the entire transformer. A damaged or "suspicious" diode is replaced with a new one. After repair, the welding machine is turned on again and checked for serviceability.

Sometimes the filter capacitor fails. In this case, the repair will consist in checking it and replacing it with a new part.

In case of serviceability of all elements of the circuit, it is necessary to deal with mains voltage, which can be greatly underestimated and is simply not enough for the normal functioning of the welding machine.

Sticky electrode (arc interruption)

The cause of sticking of the electrode and interruption of the arc may be a decrease in voltage due to a short circuit in the transformer windings, faulty diodes or loose connecting contacts. Breakdown of the capacitor filter or short circuit is also possible. individual parts on the body of the welding machine.

Organizational reasons, due to which the device does not cook as it should, include excessive length welding wires(more than 30 meters).

If sticking is accompanied by a strong hum of the transformer, this also indicates an overload in the load circuits of the device or a short circuit in the welding wires.

One of the repair options to eliminate these effects can be the restoration of the insulation of the connecting cables, as well as the tightening of loose contacts and terminal blocks.

Spontaneous shutdown

In some cases, repairs can be carried out independently if the device starts to turn off spontaneously. Most models of welding machines are equipped with protective circuit(automatic), triggered in a critical situation, accompanied by a deviation from normal operation. One of the options for such protection involves blocking the operation of the device when the ventilation module is turned off.

After a spontaneous shutdown of the welding machine, first of all, you should check the state of protection and try to return this element to working condition.

If the protective node is triggered again, it is necessary to proceed to troubleshooting using one of the methods described above related to short circuits or malfunction of individual parts.

In this situation, the first thing to do is to make sure that the cooling unit of the unit is working properly and that the overheating interior spaces excluded.

It also happens that the cooling unit does not cope with its functions due to the fact that the welding machine has been under a load exceeding allowable rate. The only right decision in this case is to let it “rest” for about 30-40 minutes, and then try to turn it on again.

In the absence of internal protection, the circuit breaker can be installed in electrical panel. To maintain the normal functioning of the welding unit, its settings must correspond to the selected modes.

So, some models of such devices (a welding inverter, in particular), in accordance with the instructions, must work according to a schedule that involves a break of 3-4 minutes after 7-8 minutes of continuous welding.

Malfunctions of inverter devices

Before repairing an inverter welding machine with your own hands, it is advisable to familiarize yourself with the principle of operation, as well as with its electronic circuit. Their knowledge will allow you to quickly identify the causes of breakdowns and try to eliminate them in a timely manner.

Wiring diagram

The operation of this device is based on the principle of double conversion of the input voltage and obtaining a constant welding current at the output by rectifying a high-frequency signal.

The use of an intermediate high-frequency signal makes it possible to obtain a compact pulse device with the ability to effectively adjust the output current.

Breakdowns of all welding inverters can be conditionally divided into the following types:

• malfunctions associated with errors in the choice of welding mode;
• failures in operation due to failure of the electronic (converting) module or other parts of the device.

The method for identifying inverter malfunctions associated with malfunctions in the operation of the circuit involves the sequential execution of operations performed according to the principle “from simple damage to more complex failure”. The nature and cause of breakdowns, as well as repair methods, can be found in more detail in the summary table.

It also provides data on the main parameters of welding, providing a trouble-free (without turning off the inverter) operation of the device.

Operation features

Maintenance and repair of welding machines inverter type differs in a number of features related to the complexity of the circuit of these electronic units. To repair them, you will need certain knowledge, as well as the ability to handle measuring instruments such as digital multimeter, oscilloscope and the like.

Under renovation electronic circuit first, a visual inspection of the boards is carried out in order to identify burnt or "suspicious" elements in the composition of individual functional modules.

If during the inspection no violations can be found, the troubleshooting continues by detecting violations in the operation of the electronic circuit (checking voltage levels and the presence of a signal at its control points).

This will require an oscilloscope and a multimeter, which should be started only if you have full confidence in your abilities. If you have any doubts about your qualifications, the only right decision would be to take (take) the device to a specialized workshop.

Complex repair specialists impulse devices they will quickly find and eliminate the malfunction that has arisen, and at the same time they will carry out maintenance of this unit.

Self-repair procedure

If you decide to repair the board yourself, we recommend using the following tips experienced professionals.

When detected during visual inspection burnt wires and parts should be replaced with new ones, and at the same time, plug all the connectors, which will eliminate the possibility of contact loss in them.

If such a repair did not lead to the desired result, you will have to start a block-by-block examination of the electronic signal conversion circuits.

To do this, it is necessary to find sources that provide diagrams of voltages and currents, designed for a more complete understanding of the operation of this unit.

Based on these diagrams, using an oscilloscope, you can sequentially check all electronic circuits and identify a node in which the normal signal conversion picture is disturbed.

One of the most complex components of an inverter welding machine is the electronic key control board, the serviceability of which can be checked using the same oscilloscope.

If you doubt the performance of this board, you can try to replace it with a working one (from another working inverter) and try to start the welding machine again.

In the event of a favorable outcome, it remains only to give your board for repair or replace it with a purchased new one. The same should be done if there are suspicions about the serviceability of all other modules or blocks of the welding machine.

In conclusion, we recall that the repair of any welding units(and inverters, in particular) is considered a rather complicated procedure that requires certain skills and the ability to handle complex measuring equipment.

If you have the slightest doubt about your professionalism, you should use the help of specialists and give them the opportunity to return the faulty device to work.

Here, the repair of the TELWIN Force 165 welding inverter will be considered. For those who are not familiar with the device and circuitry of the welding inverter, we suggest that you first familiarize yourself with the materials on this topic, namely:

In these two articles, using the example of a real TELWIN Force 165 device and a circuit diagram of TELWIN Tecnica 144-164 welding inverters, it is described in detail electronic stuffing and the purpose of each circuit element.

But let's get back to our faulty machine - the TELWIN Force 165 welding inverter. According to the owner, the machine worked properly, but suddenly, after a short break in work, it completely refused to perform its duties. When trying to start work, the spark did not appear, and an unnatural sound for regular work"hum" and "squeak".

According to the owner, it was also known that the device seemed to be working - the noise of the blower fan was heard, the indicator of normal operation turned on. And this indicates that the inverter transistors are working.

One got the impression that the welding inverter "goes into protection" - the internal protective circuits are triggered, which are part of any pulse unit, especially such a powerful one.

I started troubleshooting the welding inverter in an unusual way. The instrument did not turn on.

I had not come across such devices before, and they were new to me. Therefore, the first thing I did was open the case and began to check all the details hitherto known to me with a multimeter.

On the printed circuit board welding inverter found familiar elements: a fan, a powerful diode bridge (a radiator is installed on it), high-voltage electrolytic filter capacitors, an EMC filter, key powerful inverter transistors (installed on a radiator), a pulse transformer, an electromagnetic relay ...

An unpleasant surprise turned out to be that the surface of the printed circuit board was filled with some kind of varnish, which made it difficult to read the markings of SMD elements and microcircuits.

Protective elements were also found. One of them is a thermal fuse at 90 0 C. It is glued to the radiator of the diode bridge.

As far as I know, such thermal fuses work tightly, that is, if they heat up above their response temperature, they open forever. Similar thermal fuses can be found in power transformers. There they are included in the primary circuit and glued to it. Protect the transformer from overheating. Sometimes it can be falsely judged that the primary winding of the transformer is open, although it is worth removing (or short-circuiting) this very thermal fuse, as it turns out that the transformer is working.

Therefore, the first thing I checked was the integrity of the thermal fuse at 90 0 C. It turned out to be working.

In addition, on one of the radiators, to which powerful inverter key transistors are attached, there is also temperature sensor. Outwardly, it is very similar to the KSD series thermal switch, which is used in thermopots, water heaters and other household electrical appliances.

The peculiarity of these thermal switches is that their contacts close again if the temperature drops below a certain value. It is clear that this temperature sensor monitors the heating of powerful key transistors and, if there is overheating, temporarily disables the operation of the welding inverter. As soon as the radiators, and, consequently, the transistors, cool down, the device will start up again and will work in normal mode.

When checking the thermal switch, it turned out that it was also working. Well, well, let's look for a malfunction further.

After a short search, it was decided to test the powerful rectifier diodes. On the printed circuit board, they are located in a row and are securely screwed to the radiator with screws. The pages of the site have already talked about how to check the diode.

Labeled as 60CPH03. These are ultra-fast dual diodes VS-60CPH03.

After checking, it turned out that all three dual diodes were approximately faulty. But this is just an assumption, since the diodes are soldered into the circuit, and it is impossible to say 100% that they are faulty. Despite this, it became clear in which direction to "dig" further.

It would be possible to understand the problem without a diagram, but it is more interesting with it, especially since the repair manual for TELWIN Tecnica 144-164 welding inverters was at hand, which, frankly, differ little in their composition and circuitry from TELWIN Force 165. If you look at circuit diagram, then you can see that even if one of the 60CPH03 dual diodes breaks down, all other diodes will also be “faulty” during the check if they are not removed from the board and checked individually. Here is a piece of the circuit - the output rectifier.

As it turned out, it is not so easy to solder these very diodes. Firstly, the soldering is very decent and of high quality. And how is it different here, because huge currents flow in the power section of the welding machine, up to 130 amperes! The slightest lack of solder and the contact point will heat up, and this will subsequently lead to a malfunction. Therefore, the Italians do not spare solder and reliably flavor the contact point with it.

Do not forget that modern electronics are made using lead-free solders, and their melting point is usually higher than that of conventional tin-lead.

Before soldering the diodes, it is necessary to dismantle the radiator. The screws that secure the diodes to the radiator are non-standard, but you can unscrew them with pliers.

For desoldering, it is better to use a more powerful soldering iron. It is better to take an ordinary soldering iron with a power of 50 watts, otherwise the desoldering will turn into torment. You can, of course, use a 40-watt soldering iron, but this will require skill and a lot of patience. It is necessary to have time to warm up all 3 outputs of the diode at the same time.

When dismantling, you can try using a copper braid or desolder to remove solder. True, if the soldering iron is low-power (for example, 40 watts), then there will be little sense from them. The solder will solidify instantly.

Despite the difficulties caused by the low power of the soldering iron (I have it at 40 watts) and the burnt copper tip, I still managed to solder the dual diodes. Unfortunately, not without "jambs".

I tore out the through metallization of copper tracks with roots. Oh well, no problem. We'll clean it up and fix it up.

It turned out that one of the diodes was broken - the rest were intact. It is worth noting that both diodes, which are part of one dual diode, turned out to be broken. Now this is not a diode - but a "sieve" - ​​an ordinary conductor in a beautiful case.

If you look at the circuit, then the diode, which is indicated by a red circle, “flew out”.

Let me remind you that a piece of the circuit is taken from the manual for TELWIN Tecnica 144-164. And he repaired TELWIN Force 165. The Telvin Force 165 does not have an L1 inductor (choke) on the board and, apparently, it should not be, since seat not on the board for it. So don't pay any attention to her. In reality, this coil is made of copper wire large section to withstand currents up to 140 amperes.

It was decided to leave the device alone and look for a replacement for the faulty VS-60CPH03 diode. Finding a replacement for the 60CPH03 diode was not so easy. It was not possible to buy this radio component on the Internet. For some reason, such a detail is a rarity in online stores (perhaps everything has already changed). I had to go to the radio market and buy there.

An analogue of a diode with marking was bought STTH6003CW. The price turned out to be decent, and it was not easy to find the right one.

The parameters of STTH6003CW are the same as those of VS-60CPH03, namely:

Frame - TO-247;

Maximum current in direct connection I F(AV)– 30A for 1 element (60A for both diodes);

Permissible reverse voltage VRRM– 300V;

Recovery time (or performance) t rr (max)– 50 ns (50 nanoseconds).

Dual diode STTH6003CW refers to the so-called fast diodes. Bourgeois call such diodes Ultra-fast, Hyperfast, super-fast, Stealth diode, High frequency secondary rectifier etc. In general, as soon as they do not try to emphasize their steepness.

The main feature of a fast diode is the ability to quickly open (pass current) and also close quickly (not pass current). This means that it can operate at high frequencies. This is required for operation in the welding inverter rectifier, since it is required to rectify high-frequency current - tens of kilohertz.

Therefore, it is worth replacing such diodes only with high-speed ones!

To replace a diode VS-60CPH03 fit STTH6003CW, FFH30US30DN. All these diodes are analogues and are great for replacing each other. Actively used in welding machines. Also suitable STTH6003 TV , but it has a different body ( ISOTOP), although if there is no other, then if you wish, you can contrive and screw it somewhere.

When installing diodes on a heatsink, it is imperative to use a heat-conducting paste (for example, KPT-8).

You should not be greedy, but you should not over-paste the place of thermal contact. We apply a small, even layer of paste to the area of ​​​​contact between the diode body and aluminum radiator. Then we securely fasten the diode case to the radiator with a screw.

The installation of diodes on a radiator should be taken seriously. During operation, the diodes get very hot and the slightest difficulty with cooling will cause them to overheat and fail.

When installing diodes, it is necessary to solder the junctions of the leads and contacts of the copper tracks as best as possible. This is very important, since the currents are simply huge and if you cheat, then nothing good will come of it.

If, during dismantling, copper nickels and copper tracks were “torn off”, then they can be built up with tinned copper wire and soldered with high quality. Purely electrical contact not enough - soldering must be reliable.

After replacing the faulty diode, the device started working.

An archive with diagrams for welding machines TELWIN Tecnica 141-161, TELWIN Tecnica 144-164 and TELWIN Tecnica 150, 152, 170, 168GE can be downloaded and. File size - 4.4 Mb.