The overheating lamp is on while welding. Breakdowns and repairs of various types of Resanta welding machines. Inverter machines - a new generation of manual welding

02.09.2019

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Repairs will be discussed here welding inverter TELWIN Force 165. For those who are not familiar with the structure and circuitry of a 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 machine and a circuit diagram of TELWIN Tecnica 144-164 welding inverters, the electronic filling and purpose of each circuit element are described in detail.

But let's return to our faulty device - the TELWIN Force 165 welding inverter. According to the owner, the device was working properly, but suddenly, after a short break in work, it completely refused to perform its duties. When trying to start work, a spark did not appear, and an unnatural sound was heard from inside the case. 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, and the normal operation indicator turned on. This indicates that the inverter transistors are working properly.

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

I started troubleshooting the welding inverter in an unconventional way. I did not turn on the device.

I had never encountered 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 of the welding inverter I 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 transistors of the inverter (installed on the radiator), a pulse transformer, an electromagnetic relay...

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

Were also discovered protective elements. One of them is a 90 0 C thermal fuse. It is glued to the radiator of the diode bridge.

As far as I know, such thermal fuses operate permanently, that is, if they heat up above their operating temperature, they open forever. Similar thermal fuses can be found in power transformers. There they are included in the circuit of the primary winding and glued to it. Protect the transformer from overheating. Sometimes you can falsely judge that the primary winding of the transformer is broken, although as soon as you remove (or short-circuit) this same thermal fuse, it turns out that the transformer is working.

Therefore, the first thing I did was check 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 the powerful key transistors of the inverter are attached, there is also temperature sensor. Externally, it is very similar to the KSD series thermal switch, which are used in thermopots, water heaters and other household electrical equipment.

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 turns off the operation of the welding inverter. As soon as the radiators, and, consequently, the transistors, cool down, the device will start up again and operate normally.

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

After some searching, it was decided to test powerful rectifier diodes. On the printed circuit board they are arranged in a row and 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 we needed to “dig” further.

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

As it turned out, desoldering these same diodes is not so easy. Firstly, the soldering is very decent and high quality. And how could it be different, because huge currents flow in the power part 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 area with it.

Don't 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 a regular soldering iron with a power of 50 watts, otherwise desoldering will turn into torture. You can, of course, use a 40-watt soldering iron, but this will require skill and a lot of patience. You need to have time to thoroughly warm up all 3 leads of the diode at the same time.

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

Despite the difficulties caused by the low power of the soldering iron (I have a 40-watt soldering iron) and the burnt copper tip, I still managed to desolder the dual diodes. Unfortunately, not without its “jambs”.

I tore out by the roots the through metallization of the copper tracks. Oh, okay, no problem. Let's clean it up and build 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 diagram, the diode indicated by the red circle has “flyed out”.

Let me remind you that a piece of the circuit is taken from the manual for TELWIN Tecnica 144-164. And I was repairing TELWIN Force 165. Telvin Force 165 does not have an L1 inductor on the board (inductor) and, apparently, should not have it, since seat there is no one for it on the board. So don't pay any attention to her. In reality, this coil is made of copper wire large cross-section to withstand currents up to 140 amperes.

It was decided to leave the device alone and start looking 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 rare in online stores (perhaps everything has already changed). I had to go to the radio market and buy there.

An analog diode with markings was purchased STTH6003CW. His price turned out to be decent, and finding the right one was not easy.

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

Frame - TO-247;

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

Allowable reverse voltage V RRM– 300V;

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

The STTH6003CW dual diode belongs to the so-called high-speed diodes. The bourgeoisie call such diodes names Ultra-fast, Hyperfast, Super-fast, Stealth diode, High frequency secondary rectifier and so on. In general, as soon as they don’t try to emphasize their coolness.

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

Therefore, such diodes should only be replaced with high-speed ones!

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

When installing diodes on a radiator, it is necessary to use thermal conductive paste (for example, KPT-8).

You shouldn’t be greedy, but you shouldn’t overly spread the paste on the area of thermal contact. Apply a small, even layer of paste to the contact area of the diode body and aluminum radiator. Then securely screw the diode housing to the radiator with a screw.

Installing 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 connection points 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, nothing good will come of it.

If during dismantling the copper coins 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. File size - 4.4 Mb.

Inverter welding machines are becoming increasingly popular among welders due to their compact size, low weight and reasonable prices. Like any other equipment, these devices can fail due to improper use or due to design flaws. In some cases, repair of inverter welding machines You can do it yourself by studying the design of the inverter, but there are breakdowns that can only be repaired at a service center.

Welding inverters, depending on the model, work like household ones electrical network(220 V) and three-phase (380 V). The only thing that needs to be taken into account when connecting the device to a household network is its power consumption. If it exceeds the capabilities of the electrical wiring, then the unit will not operate if the network is drained.

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

How does an inverter work?

Below is a diagram that clearly shows the principle of operation of a welding inverter.

So, the operating principle of this welding machine module 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 alternating, but as it passes through the diode block, becomes permanent. The rectified current is supplied to the inverter, where it is converted back into alternating current, but with changed frequency characteristics, that is, it becomes high-frequency. Next, the high-frequency voltage is lowered by a transformer to 60-70 V with a simultaneous increase in current. At the next stage, the current again enters the rectifier, where it is converted into direct current, after which it is supplied to the output terminals of the unit. All current conversions controlled microprocessor unit management.

Causes of inverter failures

Modern inverters, especially those made on the basis of an IGBT module, are quite demanding in terms of operating rules. This is explained by the fact that when the unit is operating, its internal modules generate a lot of heat. Although radiators and a fan are used to remove heat from power components 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, which imply periodically turning off the unit to cool down.

This rule is usually called “On Duration” (DS), which is measured as a percentage. Without observing the PV, the main components of the device overheat and fail. If this happens to 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 the presence of dust in the air cannot be eliminated, it is necessary to open the inverter housing more often and clean all components of the device from accumulated contaminants.

But most often inverters fail when they work at low temperatures. Breakdowns occur due to the appearance of condensation on the 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 fix a malfunction in this unit. In addition, diode bridges, transistor units, transformers and other parts of the electrical circuit of the device may fail. To carry out diagnostics yourself, you need to have certain knowledge and skills in working with such measuring instruments, like 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 damaged, and repairing the welding inverter will cost half the cost of a new unit.

Main malfunctions of the unit and their diagnostics

As already mentioned, inverters fail due to the impact on the “vital” units of the device external factors. 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 the operation of inverters are:

The device does not turn on

Very often this breakdown is caused malfunction network cable apparatus. 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 method of repairing the “duty room” using the example of a Resanta brand inverter is shown in this video.

Welding arc instability or metal spattering

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

Advice! If there are no recommended current values on the packaging for the electrodes, then it can be calculated using the following formula: for each millimeter of equipment there should be a welding current in the range of 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, to ensure that the current strength corresponds to the diameter of the additive, you can use the table below.

Welding current is not adjustable

If not regulated welding current, the reason may be regulator failure or a violation of the contacts of the wires connected to it. It is necessary to remove the unit casing and check the reliability of the conductor connections, and, if necessary, test 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 detected in these modules, they must be replaced or rewound by a specialist.

High power consumption

Excessive power consumption, even if the device is without load, most often causes turn-to-turn short circuit in one of the transformers. In this case, you will not be able to repair them yourself. You need to take the transformer to a mechanic to rewind it.

The electrode sticks to the metal

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

Often, a drop in voltage causing electrode sticking occurs when using a power extension cord that is too long. In this case, the problem is solved by connecting the inverter to the generator.

Overheat light on

If the indicator is on, this indicates overheating of the main modules of the unit. Also, the device may turn off spontaneously, which indicates when thermal protection is triggered. To prevent these interruptions in the operation of the unit from occurring in the future, you again need to adhere to correct mode ON duration (DS). For example, if duty cycle = 70%, then the device should operate in the following mode: after 7 minutes of operation, the unit will be given 3 minutes to cool down.

In fact, there can be quite a lot of different breakdowns and the reasons that cause them, and it’s difficult to list them all. Therefore, it is better to immediately understand what algorithm is used to diagnose a welding inverter in search of faults. You can find out how the device is diagnosed by watching the following tutorial.

When buying an inverter welding machine for work in a garage or in a country house, the first thought is - wow, now I can cook everything! No welding diploma required, the device is designed for users 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 machines - a new generation of manual welding

Since the beginning of 2000, inverter welding machines have become cheaper and more accessible. To carry out welding work at home, it is enough to have this small and easy-to-use device and good electrodes.

Advantages of inverters

Inverter machines are lightweight, compact in size, and their scope of use and welding quality are higher than those of heavy and bulky ones welding transformers. They carry out their task in full: they weld cars, gates, pipe structures (for example, greenhouses or gazebos). Working with them is mobile - throwing an extendable belt over your shoulder, welding is carried out in any hard-to-reach places.

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

There are also no problems with the connection; the welding machine operates from a regular electrical network. It's great that it won't stop when going down mains voltage. 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 device

How welding inverters work

The inverter unit connects parts with direct current using electric arc welding with a coated electrode. The 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 uninterrupted operation electrical circuit and soft ignition of the arc with its further automatic maintenance. When connected to electrical outlet AC mains voltage with a frequency of 50 Hz is converted first into direct voltage and then into 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 the welding current value and protection against overheating.

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 operating mode of inverter welding machines is MMA. This is manual arc welding with piece coating electrodes. For welding steel and cast iron products on direct or alternating current, a diameter of 1.6–5.0 mm is used.

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

Welding machine design

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 understanding of its design.

DIY inverter assembly diagram

Craftsmen with knowledge of electrical engineering assemble the welding machine themselves. Not only for the sake of economy, but also at the behest creative soul. The Internet contains schematic diagrams of inverters, drawings and instructions from those who made the inverter themselves. The main thing is to get stability welding arc. Most often, an “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, which open and close synchronously

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

Video: review of the Barmaley scheme

DIY 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 inductor is controlled by transistors and a capacitor with stored energy. The throttle control system uses diodes;
power unit, with the participation of which a full cycle of current conversion takes place. 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 install a resonant choke and 6–10 resonant capacitors;
protective block. More often collected on power block, installing thermal switches for thermal protection of its elements. To avoid overloads, install a board based on the 561LA7 chip. Snubbers with resistors and capacitors K78–2 protect the converter and rectifiers.

Video: assembling a welding inverter

Reasons for failure of inverters

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

low protection from dust. When it accumulates inside, a thermal protection signal is triggered and the device turns off. Requires disassembly at least twice a year to clean the internal parts with a jet compressed air or with a soft brush;
moisture getting inside, causing short circuit, dangerous for the unit;
low quality 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 located inside it. Such devices are much more expensive;
voltage surges, especially drops to 190 V or more;
overload when cutting thick metal and work for which a particular device 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 used for repairs;
violation of the permissible temperature regime. Electronic microprocessors melt and destroy when overheated. It is recommended to adhere to the range from -10 to +40 o C.

Frequent breakdowns of welding inverters

Malfunctions can be either mechanical or related to electronic failure. Welding machine - complex device, problems can arise anywhere:

Short circuit or breakdown in any important node electrical circuit makes it impossible to operate the welding machine:

a malfunction of the control board does not provide a stable welding current and does not allow a normal arc to be obtained;
damage to the transistor on the upper printed circuit board leads to the device shutting down;
Failure of the overheating protection system is determined by the smell of burnt insulation and smoke coming from inside the housing.

Methods for repairing inverter welding machines

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

What can be fixed without opening it?

Poor performance of the device does not always mean internal failure. Wet or poor-quality electrodes are often the culprit. If drying or replacement does not produce a beautiful seam, consider other possible reasons:

poor ignition, sticking of electrodes to the metal often occurs due to loss of power in the work cables or low welding current. Correct selection of cable cross-section and increasing the current strength can solve the problem. Do not use power extension cords with a wire cross-section of less than 2.5 mm 2 or more long length. Optimal length up to 15 m, maximum - 40 m, otherwise the device will not work due to loss of current. Welding cable is recommended up to 5 m long;
To connect the welding machine, you must use an extension cord with a wire with a cross-section of at least 2.5 square meters. mm and length no more than 40 m
interruption, pulsation of the arc causes instability or low welding current. Check the reliability of the connections or increase the current. If there are significant voltage surges in the network, use a stabilizer;
Strong spattering of metal is caused by high welding current or incorrect polarity. The issue is solved by reducing the current strength and maintaining polarity;
humped, with undercuts, the seam is corrected by increasing the current and correct installation polarity;
porous seam with big amount defects are caused by 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 treated surfaces, incorrect polarity or too far distance of the electrode from the welding site

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

Table: correspondence between the diameter of the electrodes and the thickness of the metal

Internal organization

To be able to repair a welding machine yourself, you first need to understand its internal structure. The front panel contains sockets for working cables, a current control knob and a power indicator. If the design provides additional functions, operating indicators are located here.

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

The check begins with an external inspection of the device. First of all, check the availability mechanical damage. If there are black spots on the case, most likely there is a short circuit. The tester checks fuses, replaces them if necessary, and examines the insulation of welding cables and connections in sockets. If necessary, tighten the bolts and clean the contacts.

After unscrewing the screws and removing the casing, the interior of the device is revealed, where the following components are located:

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

Tools for work

The following tools will be required for repairs: .

DIY 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 do harm. Without knowing the rules for handling the board and the technology of such delicate work, you can cause damage much greater than the initial one. It is cheaper and safer to entrust the repair to a professional.

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

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

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

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

Power diodes. To check their continuity, the tester is switched to diode mode, and the probes are touched to 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 only ring in one direction, then the power diodes are working properly
Power transistors. Power transistors are the most vulnerable parts in the inverter. Keep in mind that when transistors are arranged in blocks, due to one faulty one, the entire arm does not work. They are checked in the following sequence:
Contact in the button. It is checked in ringing mode by placing the button in the “on” position. If the contacts ring, the button works.
The button is checked in the “on” mode by ringing its contacts
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 the 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 the red one. Then vice versa - red is placed on the negative terminal of the diode, black on each terminal of the network bridge. If the tester shows numbers everywhere, there is no short circuit, the diode bridges are fine.
The diode bridge is tested by touching each of its terminals in turn.
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 working.
The field-effect transistor in the primary power supply rings in the same sequence as the power transistors
Power nodes. If you don’t have an oscilloscope, use a tester that is set to voltage testing mode. The device is connected to the network via a light bulb. If there is voltage at the output, the light will light up, i.e. the components are working.
If the light bulb connected in series with the device lights up, the power units are working properly
Charging resistor. Break charger possible if the light does not light up when the device is turned on. Check the serial circuit of the PTC and NTC, which ensures the charge of the capacitor. The resistance breaks off when the diode bridges or power transistors are short-circuited.
To check the charging resistor, check the serial chain of PTC and NTC
Key management board. This is a complex element of the inverter, on the functioning of which the operation of the entire device depends. Check the switched on device in voltage mode up to 20 V. Set the regulator to the minimum position, the black probe is installed on the terminal, the red probe on the sixth pin. 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 control board is carried out with a tester when the device is turned on in voltage mode up to 20 V
Feedback interruption. Turn on the device, set the voltage on the tester to 20 V. The black probe is placed on the terminal, the red one on the second terminal. A 200 A device will display a voltage of 14–50 mV. If there is a break in the shunt feedback, the tester will show about 500 mV. This means there is no feedback somewhere.
When searching for a break in the reverse connection, the red probe is installed on the second pin of the microcircuit
Power unit. In the “on” mode, check for the presence of a voltage of 300 V from the capacitor to the inverter board. Check the integrity of the circuit and transistor. At the output of the power supply, two diodes provide 25 V. If the ringing shows that there is no short circuit, the secondary circuits do not load the power supply, it will start. If there is no startup, the optocoupler or transistor may be broken. If the power supply starts for a short time and then is disconnected from the network, check the transistor. If it gets hot, it means that the diode nearby is broken and needs to be replaced.
Before checking the power supply, unplug the device from the outlet!

At the first stage of repairing the power supply, check for the presence of a voltage of 300 V on the inverter board

When doing self-repairs, craftsmen use phosphoric acid. If something needs to be soldered to the diode cases (for example, broken stands), they are first tinned. When repairing a broken post, perpendicularity is taken into account. It is important to install it, clearly aligning the holes. If you solder even with minimal distortion, the post will break again when you subsequently tighten the fastener.

If not technical hair dryer, for soldering use a 100–150 W soldering iron. This will prevent damage to the connectors and tracks. Experts recommend for best result Before soldering, heat the block to 160–170 0 C, while the plastic parts of the fan must not be heated. When working with a soldering iron or other heating elements Care is required to avoid touching fusible parts of the device.

Video: repair of a welding machine and analysis of its main faults

An inverter welding machine is confidently prescribed in home workshops. Before purchasing, it is worth spending 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. Complex cases It's better to leave it to specialists.

Welding inverter is modern equipment, the use of which in the welding process makes it possible to achieve very High Quality work and provides the welder with 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 occurring during its operation.

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

malfunctions associated with improper 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 yourself in order to identify a breakdown, you need to check whether all operating mode settings are set correctly, and in addition, you should read the operating instructions for this device again, to determine if you are making any mistakes while working. Most manufacturers, when drawing up instructions, indicate the causes of welding inverter malfunctions that may occur during operation, and also describe how these malfunctions can be eliminated independently.

Causes of breakdowns of welding inverters and options for eliminating them.

There are a number typical faults, which arise when we're talking about about welding inverters:

instability of the welding arc and strong spattering of metal;
sticking welding electrode;
lack of welding process when the machine is turned on;
lack of response from 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 welding inverters.

Instability of the welding arc and strong spattering of metal.

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

Welding electrode sticking.

In fact, there may be several reasons for this type of malfunction. It is quite possible that during welding the voltage in the network suddenly decreased, which led to severe sticking of the welding electrode. It can also “stick” if the inverter is connected to the network with a cable with a cross-section that is too small. 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 of 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 lack of mass on the surface of the part being welded. In addition, it would be useful to check the condition of the welding cable - it may be damaged. This situation occurs quite often if the part being welded is heavy, as a result of which the part falling onto the wire can damage its integrity.

The device does not respond when turned on.

If nothing happens when you turn on the welding inverter, 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 device cannot operate. Another reason that the device does not turn on may be an incorrectly selected circuit breaker, installed in the shield. A weak switch can turn off when the inverter is turned on. In addition, turning off the device can lead to a loss of electricity throughout the house.

In addition to the indicated malfunctions, there are also interruptions in the operation of the welding inverter, which are not related to the breakdown of the device, but are a consequence of the fairly high-quality and timely operation of the protection systems with which the inverter is equipped. So, for example, with long-term continuous operation The inverter may turn off 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, allow the device to cool, after which work can be continued.

The welding inverter provides good quality carrying out welding work, creating the most comfortable working conditions for the welder. However, these advantages lead to increased complexity of its design. This may cause various malfunctions welding inverter and reduces its reliability.

Features of inverter repair

Unlike conventional welding machines, which are electrical products, a welding inverter is an electronic device. Consequently, diagnostics and repair of inverter welding machines are carried out by checking the operating condition of diode bridges, transistor connections, zener diodes and other parts that are included in the electronic circuits. In this case, you need to have skills in handling oscilloscopes, voltmeters, multimeters and other measuring instruments.

Home distinctive feature When repairing a welding inverter, it is difficult to determine the nature of the breakdown and detect the failed part. Therefore, it is very often necessary to diagnose all components of the electrical circuit.

Based on the above, we can conclude that it is necessary to have minimal knowledge in the field of electronics and be able to understand the design of electrical circuits. If such skills and abilities are missing, then take on do-it-yourself repair Such a device is not recommended so as not to waste extra effort and time.

Operating principle of the inverter

The operating principle of inverter devices is the sequential (step-by-step) transformation of the incoming electric current signal:

the process of rectifying incoming network currents using a special rectifier;
the process of converting rectified currents into alternating high-frequency signals;
process of reducing currents from high voltage up to the welding voltage occurring on the power transformer;
transformation alternating current with high frequency D.C., occurring using the output rectifier.

To perform such operations, the welding inverter design has several modules with electronic stuffing. The main module is the input current rectifier. Then there is a control board on which transistors (switches) are located, and it ends with a rectifier for the output signals.

At the same time, in devices different manufacturers having different models, the layout of the unit components can be very diverse, but the installation of the main components will always remain unchanged.

Therefore, knowing the basic operating principle of such units and the location of the main modules of their design, it is possible to diagnose possible faults and carry out the necessary repairs.

Types of main faults

If the welding inverter fails, the first thing you should do is check its transistors, since they are one of the most weak points such units. Initially, you should carry out visual inspection transistors. Such a broken part is very easy to identify: it has a broken or cracked case with burnt-out leads at the solder points on the board. This part needs to be replaced immediately.

New transistors should be installed on a special thermal paste. It will ensure heat removal from the transistor to a radiator made of aluminum. But very often a visual inspection does not reveal faulty elements, then you should make a “diagnosis” using a multimeter.

Replacement faulty elements carried out according to precisely specified parameters. In some cases, it is possible to supply analogue parts, and the required parameters can be determined from the datashift. If replacing the burnt-out transistors does not help, you need to move on to further diagnostics.

IN normal mode operation, transistors cannot simply fail; most likely, this is due to the incorrect operation of other elements. Most often this is the driver. It is checked with an ohmmeter. If faulty parts are found, they must be removed and replaced with similar parts.

Then the input and output current rectifiers, which consist of diode bridges, are checked. They are installed on the radiator and are reliable components for welding inverters. But they can also fail. Their functionality is checked using a voltmeter.

Control board fault

It is best to check diode bridges by unsoldering the wires from them and then detaching them from the board. This can make everything easier further work and there will be no doubt when a short circuit occurs in the entire inverter circuit.

The check follows a fairly simple algorithm. It is necessary to “ring” the entire group of parts. If a “short” is detected, then you should search for a broken diode. Once it is detected, the diode should be carefully removed and replaced.

If, after carrying out all the above steps, the welding machine still does not work, you should test the control board. It monitors the operation (control) of the keys. The reliability of all equipment will depend on the reliability of such a board.

To carry out competent and qualified repair of the inverter, it is necessary to check for the presence of the necessary signals that produce its operation. These signals must be sent to the gate buses of the key module. You can perform a similar check using oscilloscopes.

Periodically, high heating of the inverter housing may occur. This may be due to violations of the rules for using the unit and incorrect selection of the value of the current used for welding. This can also occur when the electrodes are incorrectly selected or the unit is operated for too long. To avoid such difficulties when using the inverter, it is necessary to observe optimal modes works that are specified in the technical passport.

You can fix inverter malfunctions yourself, but this can only be done if you have the necessary diagnostic tool and experience in using it. Otherwise, it is better to seek help from specialists.