Selection of household welding machines for modern market huge - from transformer and inverter to devices plasma cutting. The main area of use of this electrical equipment for domestic purposes is repair of automobiles and motorcycles, welding work on small construction sites ( country house construction). In this article, I propose to consider some points on the modernization of household transformer welding machines using the example of BlueWeld welding model Gamma 4.185.
Let's consider schematic diagram The device - as you can see, is nothing complicated - an ordinary power transformer, with a primary winding of 220/400V, with thermal protection and a cooling fan.
The operating current of the device (from 25 to 160A) is regulated by the retractable part of the transformer core. The device is designed to work with coated electrodes from 1.5 to 4 mm in diameter. What was the prerequisite for the modernization of this device? First of all, the instability of the supply voltage in the area where it was planned to use this device - on other days it barely reached 170V (by the way, some inverter devices simply do not start at this supply voltage). In addition, the device is not initially designed for making welds with high aesthetic characteristics (for example, when using electric arc welding in the process of artistic cold forging metal or when welding thin-walled profile pipes) - in general, the main purpose of the device was to “solder” two iron blanks together. Among other things, it was very difficult to “light” the arc with this welding even at the rated supply voltage - about undervoltage there is no need to talk at all. As a result, it was decided first of all to transfer the device to D.C.(for stability electric arc and as a consequence of increasing the quality of the welded joint) as well as increasing the output voltage for more stable and easier ignition of the electrode. For these purposes, the rectifier/multiplier circuit designed by A. Trifonov was ideal - fundamental electrical diagram(a) and current-voltage characteristics (b) are shown in the figure.
A special role in this technical solution of a seemingly ordinary rectifier is played by the X1X3 jumper - by inserting it, a rectifier device is obtained from a conventional diode bridge VD1-VD4 with a low-frequency filter C1C2L1, at the output of which in idle mode we have double the voltage (compared to the operating option device without a jumper). Let's take a closer look at the operation of the circuit. A positive half-wave of voltage is supplied to the semiconductor valve VD1 and, having charged capacitor C1 to the maximum, returns to the beginning of the transformer winding. In the other half-cycle, the charge passes to the capacitor C2, and from it to the valve VD2 and further to the winding. Capacitors C1 and C2 are connected in such a way that the resulting voltage is equal to the total (double) voltage, which is supplied through the inductor to the electrode holder and thus contributes to stable ignition of the arc. When the X2X3 jumper is closed and there is no welding arc, valves VD3 and VD4 do not participate in the operation of the circuit. The main advantage of the scheme is that when applied conventional scheme bridge, there is a sharp decrease in the rectified voltage with an increase in the load current at the moment of ignition of the arc; it is necessary to install electrolytic capacitors of huge capacity - 15000 μF, and all this despite the fact that at the moment the electrode touches the surfaces to be welded and the instantaneous discharge of the high-capacity capacitor occurs, a plasma micro-explosion occurs with destruction coating of the electrode, and this impairs ignition. Now a little about the design details.
Semiconductor diodes D161 or B200 with standard radiators for them are used as diode bridge valves.
If you have 2 D161 diodes and 2 B200 diodes, you can make the bridge more compact - the diodes are made with different conductivities and the radiators can be fastened with studs directly to each other without using gaskets. As capacitors, to play it safe, I used a set of non-polar capacitors MBGO (you can use MBGCh, MBGP).
The capacity of each turned out to be 400 microfarads, which was quite enough for stable operation apparatus. The current inductor L1 is wound on the core from the TS-270 transformer with a wire with a cross-section of 10 mm square.
We wind until the window is completely filled. When assembling, we place 0.5mm thick textolite plates between the halves of the transformer core. Since it was planned to use the apparatus for welding thin-walled profile pipes, the negative terminal of the rectifier was connected to the electrode holder, and the positive terminal to the “crocodile” of the mass. The tests carried out showed the following results: stable arc ignition; reliable maintenance of the arc; excellent thermal conditions for long-term operation (10 electrodes in a row); good quality weld seams (compared to using a device without a rectifier). Conclusion - modernizing a welding machine using a Trifonov rectifier significantly improves its performance in all respects.
Semi-automatic welding You can buy it ready-made, but there are always people who try to make it with their own hands. This is not easy to do, but those who really want to assemble a semi-automatic machine with their own hands will have to prepare all the necessary components in advance.
To make a semi-automatic welding machine from an inverter, you will need the following tools and materials:
- an inverter that is capable of delivering a current of approximately 150 A;
- feeder;
- burner;
- flexible hose;
- wire spool, with some design changes;
- welding inverter;
- Control block.
Feeding mechanism in in this case deserves special attention: with its help, the electrode wire is fed along flexible hose to the welding point. Ideally, the wire feed speed should match the melting speed consumables. The feed speed of the electrode wire is very important for the welding process: the quality depends on it weld. It is necessary to provide the ability to regulate speeds to be able to work with electrode wire different sizes from various materials. The most commonly used wire diameters are: 0.8 mm, 1 mm, 1.2 mm, 1.6 mm. It is wound onto reels and charged to the welding inverter. Fully automatic feeding wire to the welding torch significantly reduces the time spent on work.
The control unit of the semi-automatic welding machine has a control channel that stabilizes the current. The action of the current is controlled by a microcontroller in pulse-width mode. The voltage on the capacitor directly depends on the filling of the pulse width mode. It is this voltage that affects the strength of the welding current.
Subtleties of the transformer
There are small subtleties when preparing a transformer. The transformer must be wrapped with copper strip (width - 40 mm, thickness - 30). The strip must first be wrapped with thermal paper (suitable from cash register). In this case, winding a simple thick wire is excluded, since it will heat up.
The secondary winding should consist of three layers of sheet metal. You need to isolate the layers from each other with fluoroplastic tape. At the output it is necessary to solder the contact ends of the secondary winding. This is done in order to increase the conductivity of currents. It is imperative to provide ventilation with a fan in the inverter housing.
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How to configure the inverter?
If you decide to make a semi-automatic machine with your own hands, first you need to turn off the power part. By the way, for the input and input rectifiers, as well as for power switches (pre-soldered to copper substrates), a power section must be provided good radiators. It is necessary to place a temperature sensor in the body of the hottest radiator. Now the power part is connected to the control unit and connected to the network. When the indicator lights up, you need to connect the oscilloscope Out1, Out2 to the wires. Now find bipolar pulses, the frequency of which should be 40-50 kHz. The time between them is adjusted by changing the input voltage. The time value should be 1.5 µs.
The pulses on the oscilloscope should be rectangular with rises of no more than 500 ns. After checking the inverter, connect it to the network. The indicator of the semi-automatic welding machine should show 120 A; if this inscription on the indicator does not light up, then it is necessary to look for and eliminate the cause low voltage in welding wires. This situation occurs if the voltage is less than 100 V. After this, it is necessary to test the welding inverter by changing the current (while constantly monitoring the voltage on the capacitor). You can then check the temperature.
After the welding inverter has been tested, it is necessary to check how it behaves under load. To do this, a 0.5 Ohm load rheostat is included in the welding wires, which must withstand a current of more than 60 A. In this state, the current is monitored using a voltmeter.
If there are discrepancies between the specified current value and its controlled value, you will have to select the resistance until a match is achieved.
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Rules for using a welding inverter
By default, when you start the inverter, the controller will automatically set the current size. If all the steps indicated earlier are performed correctly, then the welding current will be equal to 120 A. If it suddenly turns out that eights appear on the indicator, this will indicate a malfunction. Such malfunctions occur when the voltage in the welding wires does not increase above 100 V. If this happens, you will have to look for and fix the malfunction.
When everything is done correctly, a number indicating the value of the specified current should be displayed in place of the eights. Using the buttons, this value can be changed, depending on what amount of welding current is required in each specific case. The interval in which it is possible to change the current value varies from 20 A to 160 A.
It is possible to control the temperature of the inverter during the entire operating process. To do this, you need to press both buttons simultaneously. After this, it will be possible to observe the change in the temperature of the radiator, the data of which will be displayed on the indicator. Normally, the temperature of the radiator should not exceed 75°C. If the temperature rises by more than 75°C, it will immediately appear on the indicator and the inverter will start to emit an intermittent beep. If this happens, the set current will automatically drop to 20 A. Although the current will be sharply reduced, the inverter will continue to operate. This sound signal will be emitted until the display temperature returns to normal.
The indicator may display an Ert error code: this will happen if the temperature sensor is broken or shorted.
In this case, in the same way, the specified current will be reduced to 20 A.
You can make a semi-automatic machine from an inverter yourself without much difficulty if you have the appropriate technical knowledge. To make a semi-automatic machine with your own hands, you will need to prepare a certain list of mechanisms, devices, tools and materials that are part of the unit.
The semi-automatic inverter includes an inverter and a welding torch.
Preparation for manufacturing and design features
Developed by home craftsmen various schemes designing semi-automatic machines from an inverter.
The most common device diagram involves the necessary list of tools and materials:
- welding inverter, which has the ability to deliver an operating current of about 150 A;
- a feeding mechanism that ensures the supply of electrode wire to the welding zone;
- burner;
- flexible hose;
- a working reel with electrode wire, which has changes in the device;
- device control unit.
The inverter should be about 150 A.
Particular attention should be paid to the feeding mechanism. By using this structural element, the electrode wire is supplied to the burner through a flexible hose. The ideal wire feed speed corresponds to the wire melting speed. The wire feed speed indicator, which is provided by the feed mechanism, has a significant impact on the work process and the quality of the weld using a semi-automatic welding machine.
When designing a semi-automatic machine, it is necessary to provide for the possibility of changing the speed of feeding the electrode wire into the welding zone. The ability to change the feed rate of electrode material allows you to work with consumables of various diameters and materials. different materials. Most often, when operating semi-automatic welding machines, wire sizes of 0.8 mm, 1 mm, 1.2 mm and 1.6 mm are used. The wire is wound on special spools installed in the welding device.
If the wire feeding is carried out fully automatically, this significantly reduces the time required to carry out work on welding workpieces.
The semi-automatic control unit is equipped with an adjustment and stabilization channel work force current The operating current parameters are controlled by a microcontroller in pulse-width mode. The voltage on the capacitor largely depends on the pulse-width current parameter. The voltage on the latter directly affects the strength of the working welding current.
Selecting a transformer for the inverter and assembling the unit
Before independently designing a semi-automatic machine, you need to decide on the type and power welding transformer, which is planned to be installed in a semi-automatic device. It should be remembered that when using wire for welding process minimum size 0.8 mm operating welding current should be 160 A. The power of the welding transformer to produce such current should be 3 kW. When choosing a transformer, you should pay attention to the fact that a transformer with a toroidal core has less weight compared to other types of devices.
When making a transformer, several subtleties need to be taken into account. The transformer needs to be wrapped with a copper strip with dimensions (40 mm - width and 30 mm - thickness). Before using the copper strip, it is first wrapped with thermal paper. Use a regular one for winding copper wire This is not possible because it gets very hot.
The secondary winding of the transformer is made of three layers of sheet metal. The layers of tin are insulated from each other using fluoroplastic tape. At the output, the ends are soldered together to increase conductivity. In the housing where the transformer is installed, a fan is mounted to provide airflow in order to increase the cooling of system components during operation of the device.
The current in the device can be adjusted in two ways: through the primary and secondary windings. Carrying out adjustment in the first way requires the use of a thyristor adjustment circuit. This method of regulation has certain disadvantages, which are eliminated by including a relay and some switching elements in the circuit.
When applying current regulation to the secondary winding, high ripple occurs, to reduce which a thyristor circuit is used. The use of switching circuits increases the weight of the structure and the cost of installation. For this reason, the use of current control through the primary winding is considered more acceptable.
To smooth out ripples, a smoothing inductor and a capacitor with a capacity of about 50,000 microfarads are built into the secondary winding circuit. This configuration of the device allows you to smooth out voltage ripples when choosing any current control scheme.
As a gearbox for feeding wire, you can use a gearbox from a VAZ windshield wiper.
Setting up a semi-automatic inverter
When assembling a semi-automatic inverter with your own hands, it is necessary to ensure good cooling for the power switches, input and output rectifiers using radiators. A temperature sensor must also be installed in the housing. After installation of the power part of the device, it is connected to the device control unit.
The finished device can be connected to the network. After the indicator lights up, connect an oscilloscope to the device and check for correct operation. Bipolar pulses should have a frequency of 40-50 Hz, and the time between them is adjusted by changing the input voltage. The normal time interval between pulses should be 1.5 µs.
The pulses recorded by the oscilloscope must have rectangular edges with a duration of no more than 500 ns.
After checking the inverter, it is connected to the household electrical network. When connecting the device, the indicator should show 120 A. If this indicator is not reached, you need to check whether the device is assembled correctly.
After testing the device for Idling The device is tested under load. For this purpose, it is necessary to include a load in the chain of welding wires in the form of a 0.5 Ohm rheostat, which is capable of withstanding a current of more than 60 A. With this load, the current is monitored using a voltmeter.
After assembling the unit, its functionality is checked. To do this, click on the start button. Immediately after this, carbon dioxide begins to flow, after a few seconds the current is turned on, and the feeding of the electrode wire begins. When the device is turned off, the supply of operating current and electrode wire first stops, and only after a few seconds the electrovalve is closed, providing the supply of carbon dioxide to the conduction area welding work. As a valve to ensure the supply of carbon dioxide, you can use the water supply valve to the rear window of a VAZ car.
Rules for using a welding inverter and using the unit
After starting the inverter, the controller sets the current required for operation. When correct settings at the output of the device the value electric current is 120 A. Using the control unit, if necessary, the current strength can be changed in the range from 20 to 160 A. When using the unit, you should control the temperature of its heating. The heating temperature should not exceed 75º C. To control it, a temperature sensor should be installed in the device. If the temperature rises above the set maximum, the device should be turned off and given time to cool down. To improve cooling, the unit is equipped with several fans.
Semi-automatic welding machine, made on the basis of an inverter, is used to carry out the procedure for precision welding of products from various types become. In addition, the device is used for welding thin metal workpieces. The use of semi-automatic devices is common when carrying out automotive repair work body
After making semi-automatic welding from an inverter for a home, this unit becomes an indispensable device, used in household for execution large quantity various welding works.
Inverters are widely used by home and garage craftsmen. However, welding with such a machine requires certain skills from the operator. The ability to “hold the arc” is required.
In addition, arc resistance is not a constant value, so the quality of the weld directly depends on the qualifications of the welder.
All these problems fade into the background if you work with a semi-automatic welding machine.
Design features and operating principle of the semi-automatic machine
A distinctive feature of this welder is that instead of replaceable electrodes, wire is continuously fed into the welding zone.
It provides constant contact and has less resistance compared to arc welding.
Due to this, a zone of molten metal is instantly formed at the point of contact with the workpiece. The liquid mass glues the surfaces together, forming a high-quality and durable seam.
Using a semi-automatic machine, any metals can be easily welded, including non-ferrous and stainless steel. You can master welding techniques on your own; there is no need to enroll in courses. The device is very easy to operate, even for a novice welder.
In addition to the electrical part - the current source high power, the semi-automatic machine has a mechanism for continuous supply of welding wire and a torch equipped with a nozzle for creating a gaseous environment.
They work with ordinary copper-plated wire in a protective inert gas environment (usually carbon dioxide). To do this, the cylinder with a reducer is connected to a special inlet fitting on the body of the semiautomatic device.
In addition, a semi-automatic machine can cook in a self-protective environment, which is created using special spraying on welding wire. In this case, no inert gas is used.
It is the ease of operation and versatility of the semi-automatic machine that makes the unit so popular among amateur welders.
Many kits feature a two-in-one function - and a semi-automatic device in a common body. An additional outlet is made from the inverter - a terminal for connecting the holder of replaceable electrodes. 
The only serious drawback is that a high-quality semiautomatic device costs significantly more than a simple inverter. With similar characteristics, the cost differs by 3-4 times.