The inverter buzzes, but won’t weld what can happen??
So, the most common problem of welding inverters, is overheating and lack of arc (contact). Everything is clear with overheat. In this case, the inverter goes into protection and must be given time to cool down.
But what to do if there is no welding arc? Why the inverter buzzes, but refuses to weld?
The most common cause is a damaged wire or ground wire. Accordingly, no contact, no welding. And the cable is usually broken off at the electrode holder, right under the insulation.
That way you can’t see the damage, but it’s there, and you just have to pull the cable a little. All this brings confusion and certain difficulties in troubleshooting. Inverter seems to work, but it does not cook.
The construction of an inverter welder
Welding inverters, depending on the model, operate both from a domestic electrical network (220 V) and from three-phase (380 V). The only thing to consider when connecting the machine to the domestic mains is its power consumption. If it exceeds the capabilities of the electrical wiring, the unit will not work with a sagging mains.
So, the structure of an inverter welder includes the following basic modules.
- Primary rectifier unit. This block, consisting of a diode bridge, is placed at the input of the entire electrical circuit of the machine. This is where the alternating voltage from the mains is applied. To reduce the heating of the rectifier, a heat sink is attached to it. The latter is cooled by a fan (inlet) installed inside the housing of the unit. Also the diode bridge has overheat protection. It is realized by means of a temperature sensor which breaks the circuit when the diodes reach 90°.
- Capacitor filter. Connected in parallel to a diode bridge to smooth out AC pulsations and contains 2 capacitors. Each capacitor has a voltage margin of at least 400 V and a capacitance of 470 uF or more for each capacitor.
- Filter for interference suppression. during the current-conversion processes in the inverter, electromagnetic disturbances arise that can disturb the operation of other appliances connected to the circuit. To get rid of interference, a filter is installed in front of the rectifier.
- Inverter. Responsible for AC to DC conversion. The converters working in the inverters can be of two types: two-stroke half-bridge and full bridge. Below is a diagram of a half-bridge converter with 2 transistor keys, based on MOSFET or IGBT series devices, which are most often seen on medium-priced inverter machines.The circuit of a full bridge converter is more complicated and includes already 4 transistors. These types of converters are installed on the most powerful welding machines, and therefore on the most expensive ones.
Welding machine doesn‘t work
What to do if the inverter won’t turn on
In most cases, the repair of the welding machine can be carried out independently, so to speak, in the home. The only exception is the complex breakage of the electronic components of the inverter, to make such repairs on their own, the average man is not possible.
Sometimes even specialists face insurmountable difficulties when disabling inverter protection. In this case there is nothing to do but take the inverter to a specialized workshop or apply to the manufacturer’s service.
We will consider the most common causes that lead to the fact that the inverter refuses to cook or does not turn on at all. Often the cause is so trivial that it causes absolutely no difficulty in correcting problems with the inverter.
Recommendations for self-repair
Electric circuit of a welding machine.
When repairing inverter welding machines, you should follow a certain algorithm:
- When a malfunction occurs, it is necessary to immediately disconnect the electrical device from the mains, allow it to cool down and only then open the metal housing.
- Diagnosis should begin with a visual inspection of the electrical components of the inverter.Infrequent cases when the repair of the inverter welding apparatus is to replace damaged parts or solder current-conducting contacts. Capacitors that have visually increased in size or cracked transistors must be replaced first.
- If during visual inspection it was not possible to determine the cause of failure of the welding machine, it is necessary to proceed to check the parameters of the parts with a multimeter, voltmeter and oscilloscope.The most frequent breakages of the power units are connected with the malfunction of transistors.
- After the replacement of the electric elements it is necessary to proceed to the examination of the printed wires, located on the board of the inverter.If you find torn or damaged tracks on the welding tool’s circuit board, immediately repair the defect by soldering jumpers or repairing the tracks with copper wire of the required cross section.
- After finishing the work with tracks it makes sense to go to the service of connectors.If the inverter device has stopped working gradually, it is possible that bad contact in the connectors took place. In that case it is enough to measure all the pins with a multimeter and clean the connectors with an ordinary household eraser.
- Despite the fact that welding inverter faults are rarely associated with diode bridges, it is not unreasonable to check their performance.Carry out the diagnostics of the electrical element better in unsoldered form. If all the bridge legs are tested short-circuited, then you should perform a search for a faulty diode and make its replacement.
- The last step in the repair of the inverter is to check the board and control panels.Diagnosis of all board components must be made with a high-resolution oscilloscope.
If diagnostics was carried out, but it was not possible to find out what was broken in the welding machine, you should stop repairing it yourself and turn to specialized workshops.
When performing independent repair work you should not forget about safety rules:
- Do not use electrical equipment without a protective cover;
- All diagnostic and repair work should be carried out with the equipment completely deenergized;
- The removal of accumulated dust and dirt is safest carried out with an air stream generated by a compressor or a cylinder with compressed gas;
- PCBs should be cleaned using neutral solvents applied with a special brush;
- Long-term storage of electrical appliances should be done in dry rooms in a completely turned off state.
Most inverter electric appliances are supplied complete with accompanying documentation. In these documents, the most common faults and repair methods are described. The training manual should be carefully examined in case of any malfunctions, and only afterwards should repairs be commenced.
The main causes of inverter failure and their manifestation
The main reasons of failure of welding inverters are violations of rules of their operation. About the operating modes and peculiarities of maintenance of a particular machine can be found in its passport, in general, given approximately the same list of activities:
- Daily exterior inspection of the main unit and cables;
- Periodical internal cleaning of the unit with compressed air;
- Routine checking, stripping, pulling through and repairing of internal power connections
- Measuring the insulation resistance and checking the protective earthing circuits.
The main factors, the effect of which becomes the reason of the inverter’s malfunctioning:
- Sudden changes in input voltage. Its fall leads to instability and stopping the inverter operation, while a significant excess may cause failure of the input rectifier elements.
- Mineral dust. Coat the surfaces of the internal parts of the unit and clog the ribbed surfaces of the radiators for cooling diodes and transistors. It leads to infringement of a thermal mode and can cause failure of separate elements.
- Metal dust and fine chips. It gets inside the inverter through the inlet fan in the case if you work near it with grinders, sanders, etc. Can cause an internal short circuit.
- Water and high humidity. Causes oxidation of wires and contacts, can lead to a short circuit.
- External mechanical damage. Sometimes causes damage to controls and internal structural elements where electronic components are mounted.
The following describes the main faults of inverters and their causes.
Unstable arc, spattering of metal
Spattering of metal during welding is usually caused by incorrectly selected welding current. This can be caused either by human error or by a faulty current regulator or control system.
The inverter does not turn on
This phenomenon can have several causes:
- Bad contact of the earth cable clamp;
- The input voltage is too low;
- The input circuit breaker has been switched off (this can be caused by an internal short circuit);
- thermal protection is triggered.
In the latter case, wait until the machine has cooled down and try to turn it on again. If the protection trips repeatedly then the inverter requires maintenance or repair.
Increased power consumption
High no-load power consumption with normal line input voltage is usually caused by a short circuit between the windings of one of the high-frequency transformer windings. Outwardly, such fault looks like burning of insulation around its current-conducting parts and is most often accompanied by a drop in no-load voltage (sometimes two or three times). It is not difficult to dismantle and inspect the transformer yourself, but it is better to entrust the repair to someone who knows about it well.
Electrode sticking to the metal
In the first case, it is necessary to stabilize the mains power supply or use an inverter with the ability to work at a reduced voltage. On the welding circuit side, the contacts should be periodically cleaned and checked for reliability. Also, the voltage drop can be caused by cables that are not long and c.s.a. according to regulations.
Unable to adjust current
It can primarily be a faulty indicator that shows the amperage level. Also one of the most common causes is a wire break, breakage or internal wear of the potentiometer, which sets the welding current. If all of this is normal, the problem may be a faulty control system of the inverter. Only an experienced technician can figure it out and perform such repairs.
Welding machine repair and troubleshooting
Fault diagnosis of inverter welding machines. Professional tips for repair and troubleshooting.
To increase the chances of success in repairing the welding machine, it is necessary to understand a little about his device. All kinds of equipment for MMA, TIG and MIG welding have a common inverter unit, only in case of manual arc welding process is carried out by consumable electrode in cladding, and argon torch has a non-consumable tungsten electrode and a channel for shielding gas feeding. Semi-automatic machines additionally have a drum and a feeding mechanism.
The inverter unit that outputs the converted direct current for welding consists of the following elements:
The main element is the control board with the keys. These are transistor switches of the Mosfet type or more modern IGBTs. Contains 2 or 4 wrenches, respectively, are divided into half-bridge and bridge ones. They provide economical power consumption, load and fine adjustment of the welding current.
The idea of the inverter is to take AC current with frequency of 50 Hz, rectify it, convert it into AC current, but with frequency, which is many times higher. At the output, the current is rectified again and welding is performed with direct current.
When a welding machine doesn‘t work, smoke and a smell of burning comes out of it, then a diagnosis is necessary. This is how it is done at home:
Examine the boards, capacitors, transistors, terminals
Look for black marks (if something is burned out) or a weak, loose contact. Most often inverters stop working due to the burnout of one of the elements. Then the machine doesn‘t turn on at all or buzzes, but doesn‘t cook. The goal is to find the problem module and replace it or repair the contact.
Cheap Arc Welder Fan Replacement Option
If visual inspection gives nothing, diagnose with a multimeter. It is forbidden for non-specialists to tamper with a live inverter. Check the resistance and the declared parameters of voltage and current. this is the craftsman’s business. The amateur can only wire a disconnected electrical circuit.
To do this, set the switch in the multimeter in the probing mode. Often indicated by a bell or continuity check icon. Depending on the radio component that you plan to test, different methods of testing apply, as well as the choice of parameters on the multimeter. In a general sense, you need to lean one contact of the part into one probe and the other into the other. The multimeter screen should light up with a one (contact has or other marking). If the display shows zeros, you have found a burned out element (it depends on the type of radio component).
It must be unsoldered and replaced with a new one with the same marking. Soldering is best done with a tinset station so as not to flood the adjacent contacts with solder, creating a track for a short circuit after switching on:
Heat the pins of the burnt part, loosen it in the circuit board and remove it from the board
Insert the new element into the holes on the printed circuit board
Apply the solder and wait for it to solidify
To test diode bridges with a tester, as a rule, they need to be unsoldered from the general circuit beforehand, i.e.к. Sometimes they are paralleled, making it impossible to correctly identify the defective bridge.
These are the general principles of diagnosis and repair. Here is a look at the different degrees of difficulty, possible causes and solutions.
Welding inverter breakdowns can be divided by degree of difficulty. Some can be repaired with your own hands at home.
The problem is characterized by the absence of the welding arc, but a small contact is evident when the electrode is held over the product. It is a simple breakdown associated with a weak connection. Check harness and earth connections on the machine. If they are loose, secure them. Check earth connection to the unit. If it’s a homemade hook. better to tack it by welding. Even if an alligator is used, shake it to improve the contact.
Electrode sparks can be caused by wrong amperage. Sometimes the “knob” is accidentally knocked over when re-positioning the machine, if you hit it with your clothes. To avoid this, use inverters with a shield that covers the control panel. There is such, for example, on a welding machine EWM PICO 160 CEL PULS MMA
Spark, but not weld the inverter can because of the weak incoming voltage. Use a tester to check the reading at the outlet. If they are below 220V, a voltage regulator or welding machines designed to work with a lower input current will help. For example, the welding inverter RESANTA SAI-220 welds at an input voltage of 140 V. Of course, 220 A it does not give at low parameters of the input current, but will be able to weld the sheets of iron to the gate, weld a tank for dacha, etc.
The greater the voltage drop, the lower the welding current. Here is a table of voltage on the board when welding with an inverter to the limit of 160 A, showing the interdependence of parameters.
A long mains cord causes increased resistance and reduces the input current. Here, reconnecting to a closer outlet with a short wire or using inverters designed for low voltage can help.
MIG Welding Troubleshooting Part 1
Long welding leads and electrode holder also act as an increased resistance, reducing the amperage. Try to connect short cables, 3-4 m long, and repeat the arc excitation.
The electrode can stick for the same reasons as sparking: low welding current, long mains cord and welding cables, low mains voltage. But sometimes this can happen when welding thin metal. Welding current of 60-80A burns through the metal, and a low 30-50A causes the electrode to stick.
Then choose welding inverter with anti sticking function. For example ESAB BUDDY ARC it has a special mode that at low operating currents “feels” the moment of electrode sticking and supplies high current for short time. The action lasts a second, after which the amperage decreases to the value set by the welder. This is enough to prevent the electrode from sticking and the metal from burning through.
When you can’t change the amperage, it’s the switch itself. It is faulty mechanically or electrically. Remove the plastic knob and try turning the piston rod with a pair of pliers.
If the AVR does not respond, it is necessary to test its contacts with a multimeter. If it is broken, the whole regulator can be replaced by unsoldering the terminals and unscrewing it from the housing. Install a new regulator and check the operation of the machine.
If the “Mains” light is on and the fan is humming, but the welder does not weld, most likely it has overheated. Each inverter has its own ON time (OL) or load time (IL). This is given in % and indicates how many of 10 minutes the equipment can continuously work at a particular current.
Household models often have a value of SP of 30-40%, so after 5-10 minutes in a row the device goes into protection, so as not to burn out. Wait 20 or 30 minutes until the machine has cooled down and try welding again. If you need a long regular welding jobs, use the machines with the LP of 60-100%, such as an inverter BARSVELD Profi ARC-507 D for three-phase network or welder TORUS-250 Extra for two-phase, etc. Among the semiautomatic machines the Aurora PRO OVERMAN 200 has proven itself in terms of load duration
If there is no light on inverter, there may be a broken power cord. Disassemble the housing and check that the mains cable contacts are secure. Second probable reason is a big layer of dust on the board. The machine went into protection to avoid short circuit. Disassemble the case and blow out the unit with compressed air from the compressor. If no compressor, use a soft brush.
When the inverter does not turn on, check the input diode bridge and power capacitors.
To prevent welding machines from breaking down, it is important to follow a number of simple tips:
Check periodically that the mains cord and output cord are securely fastened
If the voltage is low, use units designed for drawdown
Do not overload the inverter beyond its rated capacity. Let the machine cool down
Make sure that the casing is not covered with work clothes or other materials that could delay the heat exchange
Do not place inverter in dusty areas
If you will have to weld regularly in heavy construction conditions, use welding machines with body protection rubber pads, as it is the case of argon model Svarog REAL TIG 200 or MMA semiautomatic welder ESAB Rebel EMP
Choose reliable semi-automatic machines, TIG inverters and PDS machines from trusted brands EWM, Fronius, Lincoln Electric, ESAB. Or pay attention to “professional” and “semi-professional” category, where models are designed for longer work. Then you have fewer breakages and have to repair them.
Repair of welding machine Resanta SAI190K
Continuation of home power equipment repair. This time the welding machine Resanta SAI190K was brought by a neighbor in the country with the diagnosis. the machine fell, slammed, lost consciousness, woke up, does not work 🙂 If you are really interested in this topic, please read the previous articles on this profile. mysku.ru/blog/diy/78892.html mysku.ru/blog/aliexpress/74617.html
I myself use welding machine Resanta SAI190K, but it is visually and internally different from the repaired. The new unit is much more compact, a victim of marketing and economics, the stated current of 190A there is obviously not even close. From my own experience, I will note that under the same model RASTA manages to produce different modifications of the welding machines with different circuits, parameters and dimensions. Unit Comparison
This welder in 2017g and previously did not repaired, which usually simplifies the repair. Opening and examining For comparison, the old Ransanta 190K
The cause of the fault is seen immediately The manufacturer has not put an insulating strip between the radiators of power transistors and on impact they found each other. The meeting was sincere, rousing and noisy 🙂 The most annoying thing is that the manufacturer has not put this bar on purpose, I have seen such machines without bars. It’s not hard to guess why.
The innards are from Resanta SAI160, assembled on the printed circuit board SD-mini-140-1.3 SH112 for a current of 140A 🙁 Similar to 90% of the circuit
Schematics is different from the standard Resantowski:. there is no line filter. Mains interference is guaranteed, because the half-bridge is only two transistors (previously four were used) the total capacitance of the input storage capacitors was reduced (2x560mcf). recuperation diodes are not mounted on heatsinks. no frequency drop in electrode sticking. more compact and light package
It is strange, that they forgot to remove the output choke, in the next modification it will be corrected by all means 🙂
Initial diagnostic showed that at least the power IGBT transistors failed, unscrew the heat sinks and solder transistors together with heat sinks. Installed suspicious transistors Toshiba GT50JR22. the inscription is very poorly readable, the font on both transistors is different. I break one, and there is a small crystal and a reverse diode crystal missing In principle, an oblique half-bridge normally works without reverse diodes.
For the sake of interest, I broke a new transistor to compare the insides of the new one on the right
Inside the transistors are exactly the same, and the differences in the inscriptions are caused by the different year of manufacture of the transistors. Toshiba somehow manages to build a reverse diode into the single main crystal. Earlier, I have not met such a chip, I will now bear in mind 🙂
I will change the transistors for the same, but not because they are so good (no really), but because they were already available. Parameters of original transistors 44A 115W (100ºC) 600V 1.55V (50A) 2700pF 330ns (Off) and of course, comparison of old and new transistors (all original) Additionally, found a broken demagnetizing (recuperation) diode MURF860 in plastic (8A 600V 1.2V). Who is interested in the insides of the TO-220F plastic case. the crystal is on a copper plate for better heat distribution. Here the crystal is already ground.
Usually in this circuit you put RHRP1560 or similar, and often on the heat sinks. I will change both of them to the same more powerful MUR1560G (15A 600V 1,2V).
The power supply is based on an SD6834 with an inbuilt key. PWM. familiar 3845 Output diode assemblies 60F30 (60A 300V 1,05V 40ns). 3 pcs
The repair itself: Unfortunately, the jumper, separating the power supply of the power part and the circuit power is missing. But there’s nothing wrong with it if you stick to the right sequence.
Preparing and changing the regenerative diodes To insulate the flange, I use heat shrink. Isolation is needed to prevent the diode and the heat sink from touching.
I check the elements of the driver by comparing channels and according to the diagram. In this case I was lucky and the driver was fine
I’m going to connect the welder to power line with isolating transformer, LATR and 150W bulb. Set current regulator to middle position. For convenience and safety, I made a stand of decoupling, regulation and current limitation, which is very convenient 🙂
Gradually increase LATP voltage, the lamp should not light up. The fan starts to run at a line voltage of about 55V, then the start relay is activated. 5. Continuously turn up the voltage to nominal and check all the supply voltages from the power supply. 6. Using an oscilloscope I check the pulse on the gate of both transistors with respect to their emitters
The 53kHz frequency is normal, the strange shape of pulses is due to the absence of driver load in the form of gate capacitors. Narrow pulse width due to sticking protection. Some Resantes use the same function to decrease working frequency of the converter.
I close the output of optocoupler 3IS1 (circled in red) to turn off the sticking protection and check the pulse extension to the nominal value, the frequency does not change.
Check for pulses throughout the entire line voltage range. they appear at 140V or higher.
Putting transistors on radiator, not forgetting about thermal compound (used GD900).
Screwing the radiators in place
And only then solder. You should not do the contrary. you will break transistors and printed circuit board!
I use a piece of textolite to make and install a bar so that the radiators no longer touch each other
I assemble the machine and check it on the stand and then on the ballast. The maximum current was only 136A, at the arc the current will be even less and it’s sad.
Checking up the arc. Three welds steadily, at four current is not enough (at the arc current of about 120-125A). I usually test welding four. if the maximum current can continuously burn one electrode, then it will work. But here the four was so slow, that I spared the device and tested it with the three.
There is arc afterburner in this machine, but it does not work well. The fact that the threshold of its activation is tied to the output voltage, which at no-load is tied to the mains voltage. So it turns out that the afterburner is highly dependent on line voltage. I wish they had not made it at all.
After the test, the device was returned to the owner and works fine for now.
Repair of welding inverter with your own hands
Over the last couple of decades, there have been major changes in the development of welding technology. The most popular equipment has become an inverter is a technological and modern device, which, compared to the classic welders has a lot of advantages. In addition to more advanced technical solutions from transformers and rectifiers, it differs favorably in cost.
At the center of the technical solution is a microcircuit. It was these small elements that gave the manufacturers the opportunity to stuff the equipment with extensive functionality, dramatically reducing the weight and size of the installation. But there is another side to the coin. It lies in the fact that technically more complex devices are more likely to fail. So, the main faults and repair of inverter welding machines with their own hands.
How to Fix A Welder‘s Overtemp Problems and Overheating Problems. Kevin Caron
Electrode sticking (arc interruption)
The cause of sticking of electrode and arc interruption can be a voltage drop due to a short circuit in the transformer winding, failure of diodes or loose connection contacts. There can also be breakdown of the capacitor filter or closing of some parts to the body of the welding machine.
The reasons of organizational character, as a result of which the machine doesn‘t weld as it should, include excessive length of welding wires (more than 30 meters).
If the sticking is accompanied by a loud buzzing 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 with the elimination of these effects can be the restoration of insulation of connecting cables, as well as tightening the loose contacts and terminals.