Today, welding is in demand both in assembly and in repair work. A well-made work is always highly appreciated! Therefore, every home foreman just needs welding equipment. And that is characteristic, it is not at all necessary to go to the nearest store to buy the installation. Practically each of us is able to implement the circuit of a welding inverter machine with our own hands.
What is an inverter?
Inverter welding equipment is one of the types of modern devices that has almost completely replaced all other devices based on transformers, including various rectifiers, generators. Therefore, many people begin to switch to a new type of equipment.
What is characteristic, the first inverter models appeared in the late 70s, but they have nothing to do with modern devices. The only thing that remains unchanged is the compact size and initial voltage of a conventional power supply network (sometimes three-phase power can be used).
Such equipment is desirable to have for everyone who has a garage, or in his private household. And without welding in our time it is difficult to solve any problems regarding repair, construction and other types of work. In addition, the inverter can be useful in some matters of car maintenance. Moreover, to work with him it is not necessary to have professional skills.
For clarity, below is a photo of a diagram of an inverter welding machine "Resanta 220".
But what is the actual principle of operation of such welding equipment? More about this later.
How the inverter works
As with any other welding device, the principle of operation here is based on the generation of a current of great importance for the excitation and maintenance of the welding arc. It occurs between the joined parts and the electrode, and the weld cavity is filled with molten metal, due to which a strong connection is formed. And in the end it turns monolithic.
A normal power supply network (220 Volts, frequency 50 Hz) is not enough to create the necessary arc - it is necessary to convert both current and voltage. The initial current enters the rectifier unit, where it is converted from alternating current to direct and then sent to the inverter unit. This information is important, as it will allow you to repair the inverter welding machine with your own hands with knowledge of the matter.
That's where the most interesting part begins - the current is again transformed into a variable form, but with a much higher frequency (tens of kilohertz). In devices created under industrial conditions, this is achieved thanks to high-frequency transistors and thyristors.
Then the current is supplied to the transformer to lower the voltage, by directly increasing the current strength. Next, a secondary rectifier is connected, which again makes the current constant. It is he who is fed to the welding electrode via a special cable. In addition, such devices have the ability to change polarity, due to which aluminum can be easily welded.
Technical equipment
Knowing how this invaluable equipment works, we can now proceed to consider the implementation of its circuit in practice. Understanding how to repair a welding inverter machine with your own hands will help familiarization with its technical parameters.
It should be noted that they will not be inferior to purchased devices:
- input voltage - 220 V;
- input current - 32 A;
- output current - 250 A;
- for work, it is allowed to use electrodes with a diameter of 3-5 mm, a length of 10 mm;
- As for the efficiency of a home-made device, it will not be lower than that of professional devices.
The design of the apparatus consists of the main components:
- power supply unit;
- power block;
- power key drivers.
The necessary equipment can be of the following kind:
- screwdriver set;
- knife;
- hacksaw for metal;
- a sheet of metal of small thickness (to create a case);
- soldering iron;
- elements for the chip, including copper wires and strips;
- threaded fasteners.
In addition, in the repair of welding inverter machines with their own hands, fiberglass, cash register thermal paper, a sheet of PCB, mica can be useful. For domestic needs, in most cases, single-phase welding equipment is used, which is able to be powered from a 220 V network.
Power Supply
In creating a power supply, it is important to pay attention to the transformer, because the stability of the supplied voltage will depend on this element. This element is wound on ferrite with dimensions of 7 x 7 with the formation of 4 windings (primary - I and secondary - II):
- I (number of turns 100) - a sew wire with a diameter of 0.3 mm is used.
- II first (number of turns 15) - the same wire is used, but with a slightly larger diameter: 1 mm.
- II second (number of turns 15) - and here the diameter is much smaller: already 0.2 mm.
- II third (number of turns 20) - the parameters are the same as when creating the primary winding.
Now, regarding the implementation of the circuit of a simple inverter welding machine with your own hands. The primary winding must be done evenly over the entire width of the frame. As a result, voltage drops will not have a strong effect. After the formation of the primary winding is completed, it is necessary to isolate the surface using fiberglass.
After that, a shielding should be formed from the same wire as the primary winding. At the same time, its turns should cover all of it completely. These conditions must be observed when creating all other windings, and each layer must be insulated with fiberglass or masking tape.
As for the diodes, they must be installed according to the "oblique bridge" scheme. And since these elements during the operation of improvised equipment will be very hot, you should take care of their cooling. For this, cooling radiators from old computers are suitable.
In an extreme case, for an electrical circuit of an inverter welding machine, you can find cheap options in the computer parts store. The optimal and simplest solution is the Pentium 4 or Athlon 64 parts. Moreover, two heatsinks should be attached to the diode bridge: one to the top of it (through the mica pad), and the other to the bottom (via thermal paste).
The findings of the diodes should be turned in the same direction as the contacts of the transistors, with which the direct current is transformed into alternating current. The length of the wiring for connecting the terminals should not exceed 15 cm. In this case, both units (power and inverter) must be separated by a metal sheet, which in turn is welded to the device body.
Power block
The solution to the problem of how to make a welding inverter machine with your own hands also consists of creating this unit. And its main part is also a transformer, but already lowering it. Its functional responsibilities are to reduce the potential difference and at the same time increase the current strength. To create it, you need a core 20 x 208 2000 nm in the amount of two pieces. A transformer is wound using a copper strip. Its dimensions:
- width - 40 mm;
- thickness 1/4 mm.
For thermal insulation, each layer must be covered with wear-resistant thermal paper. The secondary winding is created by three copper strips that are insulated with a fluoroplastic tape.
The use of thick wire is inappropriate and even mistaken here. After all, the transformer will work with a high-frequency current, and therefore only the use of wide wiring is relevant.
Inverter
Well, of course, how can this unit be ignored in the implementation of the circuit diagram of an inverter welding machine? Its task is to reverse convert a constant current into an alternating form, while increasing its frequency.
The best option for assembling such a unit will be the use of medium and low power transistors. In this case, it is possible to simultaneously stabilize the frequency of the current and reduce the noise level of welding home-made equipment.
The circuit is complicated by capacitors connected in series. Such a measure will allow to avoid resonant transformer emissions and reduce the losses of the transistor unit.
Features of the choice of transistors
The choice of transistors (namely, so called power switches) should be approached as competently as possible. The performance of the welding device will depend on the fulfillment of this condition. For this, the first step is to calculate the approximate power of the resulting inverter. Without this, it’s unlikely to understand how to assemble an inverter welding machine with your own hands.
For example, let it be a voltage of 24 V (the average value when the arc burns stably) and you need to get an arc of 160 A. Multiplying these values by each other, we get the useful power that the inverter will give out. In our case, it is 3.48 kW. With an efficiency of 85%, transistors must pass through this calculated power multiplied by efficiency. Ultimately, the value will be approximately 4.5 kW - this will be the desired value of the keys.
Since a conventional household electric network of 220 V will be used for the operation of welding equipment, the current strength will be 20 A (4500 watts divided by 220). In this case, you should choose transistors that can withstand a current of a given force and not an ampere less!
Cooling organization
As we know, an inverter home-made apparatus will be very hot during welding. And so much so that only cooling radiators will obviously not be enough, in this regard, care should be taken to organize a good cooling system. Otherwise, do not avoid frequent repairs of the inverter welding machine "Strat" with your own hands.
Overheating in itself is terrible in that not only do various electrical components fail - the device itself can become unusable. For this reason, in addition to radiators, it is worth using fans.
Low-power options from the computer (CPU cooling) should be at least six. But to blow the step-down transformer, you should put a powerful fan, which is also able to cool the entire system. A power transformer should also be equipped with several fans (at least 3 pieces).
To protect the welding equipment itself from overheating and to avoid its early failure, it is necessary to fix the temperature sensor on the radiator (which is heated most). Its main function is to power off the device when exceeding the maximum allowable temperature.
Housing
At the final stage of assembly of the inverter-type welding machine, do-it-yourself will require a good body, in which the equipment scheme itself will be located. For this purpose, the system unit from the old computer is quite suitable, and the older it is, the better (the metal is thicker in it). Better ATX format. To do this, you can do searches in your own garage (shed) or visit the points of disassembling computers, for sure there may offer some option.
In extreme cases, the housing can easily be made of sheet metal itself. At the same time, a canister will do. Only it is necessary to make holes for ventilation and put additional fasteners. In this case, the circuit diagram of the inverter welding machine will be additionally protected from overheating.
Apparatus assembly
Now the assembly procedure of the welding equipment itself. Electronic boards are created using 1 mm thick PCB. To reduce the load on them make several small slots. Ready-made transformer windings are fixed on the basis of the unit with the help of several brackets. In its quality, you can just take a getinaks plate 5 mm thick or a little more. It should have a slot for the fan.
When installing magnetic cores, they should be located at a small distance so that gaps are formed (for air circulation). To ensure stabilization of the current strength and the potential difference, you should assemble the inverter welding machine with your own hands on tl494.
There can be many types of home-made structures, but regardless of this, all of them have a common feature - controlling the operation of welding equipment. For this, not a front panel is a switch, a knob that regulates the current strength, wire leads, control LEDs.
Setup Stage
When the inverter is assembled, you need to tune it. Do not underestimate the importance of this procedure, since this is a prerequisite and without using it you should never use the device! To do this, you must perform certain operations.
To begin with, it is worth applying a small current value (15 V) to the PWM controller and fans. This will allow you to evaluate the health of the node. After the capacitors are charged, it is worth applying a voltage to the relay, which controls the operation of the resistor. But you can not give current directly, otherwise the simplest welding inverter machine with your own hands can simply be ruined, and immediately! But if everything is normal, you can begin to configure the modulator, making sure that rectangular pulses appear when the relay is triggered.
At the next stage of configuration, it is necessary to check the functionality of the board itself. For this, idling is set and a current of up to 100 mA is supplied to the bridge. Such a seemingly trifling stage is actually very important, because it allows us to judge the performance of the diode bridge.
It is imperative to adjust the noise level noted on the phases of the transformer device. It is better that there are no extraneous sounds in the inverter operation in phases. Otherwise, most likely, the polarity was violated - just change it. A similar noise test can be performed using any electrical household appliance. That is, a kettle with a power of at least 2.2 kW is suitable.
But it is not enough to make the simplest inverter welding machine with your own hands, it is necessary to regularly conduct diagnostics of the device, not forgetting about its maintenance. Since only with proper care and attitude can it serve faithfully for many years.
Rules for using the device
Despite some simplicity, the inverter apparatus needs a responsible attitude to its own person. Therefore, in order to avoid serious damage, as well as the failure of the device, you should follow simple rules during operation:
- Before work, you need to prepare free space - ideally, when there is a lot of it.
- It should be borne in mind that the inverter welding machine does not tolerate temperature extremes and weather conditions.
- Avoid dust accumulation, as it is a good conductor. In industrial facilities, this is being fought with compressed air equipment.
- The choice of wires for the welding cable is largely dependent on the thickness of the electrode used. As a rule, for household needs, their diameter is 3 mm, for which thin and light cables are suitable. Moreover, their length should be no more than 1.5 meters.
- Having put into practice the do-it-yourself circuit of the inverter welding machine, do not allow it to overheat! Intensive processes lead to strong heating of parts of the electrical circuit. Blown items are a fairly common problem. On average, it is worth spending from 5 to 6 minutes on continuous operation, which is quite enough.
- Immediately prior to work, it is necessary to check all wire connections to avoid interruption of the current supply.
At the same time, one should not forget about basic safety measures! That is, you need to work in special, non-burning clothing and mittens, including the use of a shield.
And if, nevertheless, a nuisance happened, the main thing is to eliminate the malfunction in time. About what major failures can occur and how to fix them - in the next section.
The main malfunctions of inverter equipment
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- The welding arc falls, and often. With a greater degree of probability, this indicates a breakdown of the winding, because of which an overstated voltage is observed in the circuit.
- Incorrect welding current adjustment. Possible closure of the clamps, choke coil or failure of the screw that regulates the current.
- Lack of current. So, the voltage has dropped in the network - it is necessary to check the operability of the regulator.
- The transformer is very noisy. Often this is a sign of overheating of the unit. In this case, you should check the fastenings that tighten the parts of the magnetic circuit, including the movement mechanisms and the core of the coil. The possibility of a short in welding wires cannot be ruled out.
- The device switches itself off. Most likely, the reason lies in the closure of the electrical circuit, which led to auto shutdown.
In addition, after creating an inverter welding machine circuit with your own hands, it is worth considering one nuance. Even such a home-made model has a weak point. And this is the terminal block with which the welding cable is connected.
In conclusion
In conclusion, I want to note a number of positive and negative aspects of improvised inverter-type devices. And the most important advantage is the ability to use welding equipment not only in the home, but also in small production.
At first glance, it seems that the design is filled with many different details, and the scheme itself is quite difficult to implement. However, if you follow the instructions, use only high-quality materials, then everything becomes not so painful. In addition, you can achieve long-term work at low cost.
As for the shortcomings, the main thing is only one - short service life with large volumes of work. Then you have to make a three-phase welding device, only a power source for this type is difficult to find.
Ultimately, to realize the scheme of an inverter welding machine with your own hands is affordable for almost any home master. It would be a desire and free time. And the benefits of such a device will be substantial!