I have never seen an inverter circuit simpler than this one. To repeat, you will need a minimum of parts - no more than 10 pieces. To obtain an output voltage of 220 volts, we need one 1.5 volt AA battery.
Inverters are needed where it is not possible to connect to a 220 volt network. Inverters are divided into two types: some have a sinusoidal output voltage with a frequency of 50 Hz and are suitable for powering almost any load. Other modified ones have a high output frequency, about 500-10000 Hz and not always a sinusoidal waveform.
Inverters with a sine wave frequency of 50 Hz are expensive, since a large transformer or simulation electronics unit is needed to generate a 50 Hz sinusoidal pulse.
The simplest inverter that we will make belongs to the second group. And suitable for powering various switching power supplies, such as phone charger, energy saving light bulb– fluorescent or LED.
Required Components
Transformer 220V – 6V. You can tear it out of an old tape recorder, receiver, etc. or buy here -AA battery housing - 1 -
Switch - 1 -
PCB - 1 -
BC547 transistor (domestic analogue of KT3102, KT315) - 1 -
BD140 Transistor with radiator (domestic analogue of KT814, KT816) – 1 -
Capacitor 0.1 µF – 1-
30 kOhm resistor - 1 -
Tools:
Soldering iron, if you don’t have it, take it here -
Scheme
Let's start getting acquainted with the inverter with a diagram. This is an ordinary multivibrator based on a composite transistor. The result is a generator at the output of which there is a step-up transformer.Let's put together a diagram. The board is prototyping, with a lot of holes. We insert the parts and solder them with jumpers according to the diagram.
Checking work
If all components of the circuit are in good working order, and the circuit is assembled without errors, then the inverter starts working immediately and does not need adjustment.
Connect to the inverter output energy saving lamp. Insert the battery and close the switch. The light came on.
Of course, its brightness is lower than when powered from the mains, but the fact that it operates from a 1.5 volt element is a breakthrough!
Naturally, as everywhere else, the law of conservation of energy applies here. Based on this, it follows that the current in the battery circuit will be several times higher than in the light bulb circuit. In general, the battery must be alkaline, then there is a chance that it will work a little longer.
When installing and working with the inverter, be especially careful, the voltage of 220 volts is dangerous to life. And, believe me, a 1.5 volt battery is enough to give a person a devastating electric shock, and even cause cardiac arrest. As you know, for this it is enough to pass about 100 mA through a person, which this inverter is quite capable of.
The designer and famous scientist Yuri Negulyaev at one time invented an almost irreplaceable device - a welding inverter. We suggest you consider how to make a welding inverter with your own hands using a pulse transformer and powerful MOSFET transistors.
The most important thing when constructing or repairing a purchased or homemade inverter is its fundamental electrical diagram. For the manufacture of our inverter, we took it from Negulyaev’s project.
Manufacturing of transformer and choke
To work we will need the following equipment:
- Ferrite core.
- Frame for transformer.
- Copper bar or wire.
- Bracket for fixing the two halves of the core.
- Heat-resistant insulating tape.
First you need to remember a simple rule: the windings are wound only over the full width of the frame; with this design, the transformer becomes more resistant to voltage surges and external influences.
A high-quality pulse transformer is wound with a copper busbar or a bundle of wires. Aluminum wires of the same cross-section are not able to withstand a sufficiently high current density in the inverter.
In this version of the transformer, the secondary winding must be wound in several layers, according to the sandwich principle. A bundle of wires with a cross-section of 2 mm, twisted together, will serve as the secondary winding. They must be isolated from each other, for example, with a varnish coating.
Winding rings There must be two or three times more insulation between the primary and secondary windings so that the mains voltage, which in rectified form is 310 volts, does not reach the secondary winding. PTFE heat-resistant insulation is best suited for this.
The transformer can also be made not on a standard core, by using for these purposes 5 transformers from horizontal scanning of faulty TVs, combined into one common core. It is also necessary to remember about the air gap between the windings and the core of the transformer, this makes it easier to cool.
Important note: the uninterrupted operation of the device directly depends not only on the size DC, but also on the thickness of the wire of the secondary winding of the transformer. That is, if we wind the winding thicker than 0.5 mm, we will get a skin effect, which does not have a very good effect on the operating mode and thermal characteristics of the transformer.
A current transformer is also made on a ferrite core, which will then be attached to the positive power wire; the outputs from this transformer go to the control board to monitor and stabilize the output current.
To reduce the ripple at the output of the device and reduce the amount of noise emissions into the power supply network, a choke is used. It is also wound on a ferrite frame of any design, with a wire or bus, the thickness of which corresponds to the thickness of the secondary winding wire.
Welding machine design
Let's look at how to construct a fairly powerful pulsed welding inverter at home.
If you repeat the design according to the Negulyaev system, then the transistors are screwed to the radiator with a plate specially cut for this purpose, thus improving the heat transfer from the transistor to the radiator. Between the radiator and the transistors it is necessary to lay a thermally conductive gasket that does not allow current to pass through. This provides protection from short circuit between two transistors.
The rectifier diodes are attached to a 6 mm thick aluminum plate; the fastening is carried out in the same way as the transistors are fastened. Their outputs are connected to each other with a bare wire with a cross-section of 4 mm. Be careful not to let the wires touch.
The choke is attached to the base of the welding machine with an iron plate, the dimensions of which follow the shape of the choke itself. To reduce vibration, a rubber seal is placed between the throttle and the body.
Video: DIY welding inverter
All power conductors inside the inverter housing must be routed in different directions, otherwise there is a possibility of a short circuit. The fan cools several radiators simultaneously, each of which is dedicated to its own part of the circuit. This design allows you to get by with just one fan installed on the rear wall of the case, which significantly saves space.
To cool a homemade welding inverter, you can use a fan from a computer case; it is optimal in both size and power. Since ventilation of the secondary winding plays a large role, this should be taken into account when positioning it.
Diagram: disassembled welding inverter The weight of such an inverter will range from 5 to 10 kg, while its welding current can range from 30 to 160 amperes.
How to configure the inverter operation
Making a homemade welding inverter is not that difficult, especially since it is an almost completely free product, except for the costs of some parts and materials. But to configure the assembled device, you may need the help of specialists. How can you do this yourself?
Instructions that make it easier to independently set up a welding inverter:
- First, you need to apply mains voltage to the inverter board, after which the unit will begin to emit the characteristic squeak of a pulse transformer. Voltage is also supplied to the cooling fan, this will prevent the structure from overheating and the operation of the device will be much more stable.
- After the power capacitors are fully charged from the network, we need to close the current-limiting resistor in their circuit. To do this, you need to check the operation of the relay, making sure that the voltage across the resistor is zero. Remember, if you connect the inverter without a current-limiting resistor, an explosion may occur!
- The use of such a resistor significantly reduces current surges when the welding machine is connected to a 220-volt network.
- Our inverter is capable of producing current in excess of 100 amperes, this value depends on the specific circuit used in the design. It is not difficult to find out this value using an oscilloscope. It is necessary to measure the frequency of incoming pulses to the transformer; they should be in the ratio of 44 and 66 percent.
- The welding mode is checked directly on the control unit by connecting a voltmeter to the output of the optocoupler amplifier. If the inverter is low-power, the average amplitude voltage should be about 15 volts.
- Then the correct assembly of the output bridge is checked; for this, a voltage of 16 volts is supplied to the inverter input from any suitable power supply. At idle, the unit consumes a current of about 100 mA, this must be taken into account when carrying out control measurements.
- For comparison, you can check the operation of an industrial inverter. Using an oscilloscope, the pulses on both windings are measured; they must correspond to each other.
- Now you need to check the operation of the welding inverter with connected power capacitors. We change the supply voltage from 16 volts to 220 volts, connecting the device directly to electrical network. Using an oscilloscope connected to the output MOSFET transistors, we monitor the waveform; it should correspond to tests at reduced voltage.
Video: welding inverter under repair.
A welding inverter is a very popular and necessary device in any activity, both in industrial enterprises and in households. In addition, due to the use of a built-in rectifier and current regulator, with the help of such a welding inverter it is possible to achieve better welding results compared to the results that can be achieved when using traditional devices whose transformers are made of electrical steel.
The welding inverter was assembled by hundreds of craftsmen with their own hands. As practice shows, there is nothing overly complicated in this process. If you have experience and desire, you can acquire the necessary parts and spend some time on the work.
To manufacture the device, you must stock up on all the necessary parts and components.
The transformer-type welding machine was so bulky and problematic to operate that the thyristor-based inverters that replaced it quickly gained universal popularity.
Further development of technologies for manufacturing semiconductor components made it possible to create powerful field effect transistors. With their advent, inverters have become even lighter and more compact. Improved conditions for adjusting and stabilizing the welding current allow even beginners to work with ease.
Selecting an inverter design
You can use an old computer unit as a case.
The layout of a homemade welding inverter is unoriginal and similar to most other designs. Most parts can be replaced with analogues. It is necessary to determine the dimensions of the device and begin manufacturing the case if all the main elements are present.
You can use ready-made radiators (from old computer power supplies or other devices). If you have an aluminum bus 2-4 mm thick and more than 30 mm wide, you can make them yourself. You can use any fan from old devices.
All dimensional parts must be placed on a flat surface, connection possibilities must be examined according to schematic diagram.
Then determine the installation location of the fan in order to hot air some parts did not heat up others. In a difficult situation, you can use two fans working for exhaust. The cost of coolers is low, the weight is also insignificant, the reliability of the entire device will increase significantly.
The largest and heaviest parts are the transformer and choke for smoothing out ripples. It is advisable to place them in the center or symmetrically along the edges so that their weight does not pull the device to one side. It is extremely inconvenient to work with a device worn on the shoulder and constantly sliding to one side during welding.
If all parts are satisfactorily located, you need to determine the dimensions of the bottom of the device and cut it from the available material. The material must be non-electrically conductive; getinax and fiberglass are usually used. If these materials are not available, you can use wood treated with fire retardants and moisture protection. The latter option in some ways has its advantages. Screws can be used to secure parts rather than threaded connections. This will somewhat simplify and reduce the cost of the manufacturing process.
Electrical circuit of the inverter
All inverters have a similar block diagram:
- input diode bridge, which converts AC mains voltage to DC;
- DC/AC converter high frequency;
- device for reducing high frequency voltage to operating voltage;
- converter to DC voltage with a filter to smooth out ripples.
Selected for homemade The scheme is arranged according to the classical method. The basis of the circuit is an oblique bridge, which provides best characteristics work with maximum simplicity and such cost. The power circuit is controlled by the TL494 controller. Control functions and welding current adjustment are performed by the PIC16F628 microcontroller. Protection of the device from overheating is also implemented through it. Depending on the maximum current and the parts used, several versions of the device firmware are possible with different maximum permissible welding current.
The power supply for the logical elements of the circuit and low-voltage equipment is made on a TNY264 PWM controller.
Schematic diagram, despite large number elements, is made quite simply. The entire control system is implemented on several boards:
- board of power elements, two options;
- rectifier;
- two control boards.
The board of power elements contains rectifier diodes with protective circuits, power transistors, a transformer, and measuring resistance. The required version of the board must be selected based on the available components for the welding inverter.
The inverter unit requires a power control board.
The rectifier board contains bridge elements, smoothing capacitors, and relays soft start, resistances that compensate for changes in parameters depending on temperature (thermistors).
The following circuits are located on the power control boards:
- PWM controller with decoupling elements based on optocouplers;
- digital indicator with control buttons;
- power supply elements;
- microcontroller.
Before assembling the boards, the tracks for installing power elements must be reinforced with copper wire with a cross-section of 2.5-4 mm. For tinning tracks, it is advisable to use refractory solder.
Transformer and choke for inverter
When making a core for a welding inverter transformer, you can use line transformers from old TVs. You will need six transformers of type TVS110PTs15.U. You need to remove the tension bracket from the transformers (unscrew the two M3 nuts and remove the bracket). The winding can be cut on both sides with a hacksaw or grinder, taking the necessary precautions. If, after removing the winding, the core does not separate into two parts, you need to clamp it in a vice and separate it with a light blow. The surfaces of the parts must be cleaned of epoxy resin. After preparing the magnetic cores, you need to make a frame. The optimal material for the frame would be fiberglass laminate with a thickness of 1-2 mm, but you can use getinaks or cardboard. Technical characteristics of the assembled magnetic circuit:
Transformers can be borrowed from an old TV.
- average length of the magnetic line kp=182 mm;
- window dimensions S 0 =6.2 cm 2;
- cross-section of the magnetic circuit S m = 11.7 cm 2;
- coercive force H c =12 A/m;
- residual magnetic induction B g =0.1 T;
- magnetic induction B s =0.45 T (if H=800 A/m), B m =0.33 T (if H=100 A/m and t=60° C).
The cross-section and number of turns of the windings must be calculated based on the maximum permissible operating current for the device.
The windings must be positioned across the entire width of the window to reduce wasteful losses.
As a material for windings, you can use copper foil or Litz wire of the required cross-section to eliminate the skin effect. The insulating material between the layers and windings can be wax paper, varnished cloth, or FUM tape.
If it is necessary to control the welding current, a current transformer can be made. To make it you will need two rings of type K30x18x7. They need to be wound with 85 turns of copper wire in varnish insulation with a cross section of 0.2-0.5 mm. The ring is placed on any of the output wires of the device.
Using an inverter in a three-phase network
Sometimes, when the network is overloaded, there is not enough power for the inverter to operate normally. If connection is possible, a single-phase inverter can be converted to a three-phase one.
When connected to a single-phase network (the plug is plugged into the socket), the starter K1 is turned on. One pair of its contacts connects the wires going from the plug to the standard switch (on/off) of the inverter. Another pair will connect the tracks cut on the board from the switch to the stationary rectifier.
Starter K1 must have contacts with a maximum permissible current of at least 25 A.
To connect voltage from a three-phase rectifier, a K2 starter is used. The maximum permissible current of its contacts must be at least 10A. To connect to three-phase network It is advisable to use a 3p + N + E socket (three phase wires, neutral and ground). The device can be built into the inverter or manufactured as a separate unit. Manufacturing as a separate block is optimal when working in one place. Carrying two devices is not convenient when you move frequently.
Conclusion on the topic
Making a welding inverter with your own hands is not so difficult. If you lack experience, you can always consult with specialists.
As a result, you can get an excellent device with additional functions that are not available in industrial inverters.
Repairing a device made by yourself will not create any special problems, and using the tool will be a pleasure.
An inverter is a fairly complex welding tool that has recently gained enormous popularity. Excellent performance due to the large number technical units, in the total mass making up one device. To achieve high quality of the resulting seam, reliable operation and good technical characteristics World manufacturers are trying to introduce new developments and make powerful, but at the same time economical equipment. But it turns out that you can make the simplest welding inverter with your own hands.
Naturally, one should not expect high modern characteristics from such devices. But it is quite possible to create everything yourself, since all the components for this are freely available and if you have a complete set and a suitable circuit, you can create an inexpensive compact model. Here you need to make the right selection based on power calculations and other parameters. In other words, all parts must be compatible with each other, both in type and parameters. For example, the most vulnerable part of the device are transistors, therefore, their selection should be approached with special attention.
Advantages
- A simple DIY welding inverter is much cheaper than ready-made models of welding machines;
- At self-assembly it is much easier to repair equipment if any problems happen to it;
- You can independently adjust the configuration based on your preferences, technical requirements and budget.
Flaws
- A simple homemade welding inverter turns out to be not so reliable in operation, even in comparison with budget types of equipment;
- It will take a significant amount of time to create the device, which is not always economically beneficial;
- Not available here additional features which will help improve the quality of the seam created;
- The equipment has a narrow range of adjustment of welding current and other parameters;
- As a rule, they have problems with the cooling system;
- The housing is not created as safely as in factory models, so the use of such devices can be life-threatening.
Design and circuit of a simple inverter
A diagram of a simple welding inverter helps determine what exactly should be included in the device. Naturally, this is not the only option and substitutions are possible. Some prefer to create more complex options, based on the diagrams of ready-made factory models, such as or, making their own changes. Here is the simplest diagram for independent implementation.
Calculation method
Before you start making the simplest welding inverter, you need to calculate its power. This is done by multiplying the current the device must have by the voltage at which the arc will burn. For example, for a current of 160 A, which will be possible at an arc voltage of 24 V, the power should be 3840 W.
Even a simple welding inverter with one transistor can have an efficiency of 85%. Thus, the power pumped by transistors should be 4517 W
Based on this value, it is possible to determine the current strength switched by the transistors during operation. To do this, you need to find the power divided by the voltage in the network. 4517/220 = 20 A.
In order to maintain a voltage of 220 V at 20 A, a filter with a capacity of 100 μF must be present in the circuit. If a large current passes through the transistors, it begins to heat them. As a rule, the rate of heat removal using radiators is insufficient, and overheating will lead to destruction of equipment. To avoid such troubles, transistors should be selected with a margin so that their operating current at 1000 degrees Celsius is at least 20 A.
A welding machine that is easy to replicate and manufacture should have a transistor voltage no greater than the voltage in the power source. Very important parameter is the frequency of the transistors. For the parameters presented above, products with a frequency of 100 kHz are suitable. The voltage on them should be 500 V. These can be either ordinary field-effect or IGBT transistors. The only problem with their installation is the lack of special fasteners.
In order for the transistor to work normally, there must be a pause between its opening and closing. The pause time should be about 1.2 ms. The only exception is Mosfet transistors, in which a pause is allowed at 0.5 ms.
Required tools and materials
In order to create a simple welding inverter using a single transistor, you should have the following set of tools:
- Screwdriver set;
- Voltmeter;
- Multimeter;
- Soldering iron;
- Oscilloscope.
These are the main tools with which assembly, control and measurement take place. In addition, you should also have the materials that will be needed to create the device itself. For this you will need:
- Resistors with different resistance levels;
- Inductor;
- Capacitors;
- Optocoupler;
- Zener diode;
- Rectifier diodes;
- Schottke diodes;
- Transformer with two windings;
- Relay;
- Trimmer resistors;
- Diode bridge;
- Protective diode;
- Linear regulator;
- Cooling fan;
- AC to DC converter.
You should apply current to the circuit to check how the resistor closure relay operates. Next comes checking the PWM board to see if it has square pulses, which may appear after the relay operates. If there are pulses, then their width in relation to the zero pause should be 44%.
You need to make sure that the voltage on the transistors does not exceed the permissible limit, otherwise all this can lead to breakdown. Power is then applied to the diode bridge to verify its correct manufacture and functionality.
During setup, you need to make sure that the transformer is wound correctly, as well as that it is connected correctly and can be controlled. This is one of the main elements that determines the adjustment of parameters, but at the same time the most difficult to implement due to the presence of a winding.
Safety precautions
All procedures must be carried out only with the power supply turned off. It is advisable to measure each part in advance so that during switching on it does not break due to overvoltage. During operation, basic electrical safety rules should be observed.
Currently, the most popular, functional and productive equipment for welding is an inverter welding machine.
An inverter is often used for welding. It is compact and easy to use.
High power field effect transistors are used as power switches in such equipment. This made it possible to significantly reduce the size and weight of the unit. A large selection of such equipment is available on the market. All available models have almost the same principle of operation. The only drawback that can eliminate the desire to buy such a unit is its fairly high cost. However, you can put in a little effort and assemble the inverter yourself.
Features of a homemade inverter welding machine
The inverter welding machine in question consists of the following main elements:
- power supply;
- power switch drivers;
- power part.
A homemade inverter welding machine will have the following characteristics:
- maximum current consumption - 32 A;
- welding current - no more than 250 A;
- mains voltage - 220 V.
Such an inverter welding machine will be able to weld without any problems using an electrode with a diameter of 3-5 mm and an arc length of up to 10 mm. The efficiency of a homemade unit is in no way inferior to ready-made store-bought welding devices.
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Preparing to assemble the welding machine
To assemble the unit you will need the following:
- electrical steel;
- cotton fabric;
- copper wires;
- fiberglass;
- textolite
To stabilize the voltage, the windings must be made across the entire width of the frame. In total, the design of the inverter welding machine under consideration will have 4 windings:
- primary - consists of 100 turns, PEV 0.3 mm;
- three secondary windings - one of 15 turns (PEV 1 mm), the other - also of 15 turns (PEV 0.2 mm), the third - of 20 turns (PEV 0.3 mm).
The board with the power supply is mounted separately. A sheet of metal will be located between it and the power part. It must be electrically attached to the body of the inverter welding machine.
Conductors will be used to control the shutters. They should be soldered at a minimum distance from the transistors. They should twist in pairs with each other. The section doesn't really matter. The length of the conductors should be no more than 15 cm.
Before assembling the inverter welding machine, you need to carefully study and understand its circuit diagram.
The power supply of the unit in question is a traditional flyback. The primary winding of the block will need to be covered with a shielding winding. It is made from the same wire. The superimposed turns must completely overlap the primary ones and have the same direction as them. There is insulation between the windings. It can be made from varnished fabric or masking tape.
When setting up the power supply of the welding machine, you need to select such a resistance so that the voltage supplied to the relay is 20-25 V. Select reliable and powerful radiator elements for the input rectifiers. Models that were used in old computers are excellent for this purpose. They can be purchased inexpensively on the radio market.
The control circuit includes only 1 thermal sensor. It will be placed inside the radiator housing. On the same radio market you should buy a PWM controller for the control unit. Through its control channel the current in the arc will be stabilized. The PWM voltage will be determined using a capacitor. The strength of the welding current depends on the voltage itself.
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Step-by-step instructions for assembling an inverter welding machine
Use winding wire to wind the inductor.
First of all, prepare all the parts indicated in the circuit diagram. To assemble such a welding inverter, you can use available materials that are sold in any radio and electronics store. Before using parts, make sure they are in working order.
Choose a ready-made choke or make it on a steel magnetic circuit. To make the inductor winding, use PEV-2 wire. You need to make 175 turns.
The most affordable capacitors that can be used to assemble such an inverter welding machine are K78 capacitors.
They were widely used in old TV sets, so finding them should not be difficult. The operating voltage of the capacitors must be at least 1000 V. If you cannot find a capacitor with the required voltage, use several elements so that their total capacitance matches the required rating.
To assemble the inverter you will need several transistors.
Buy several KU221A transistors of low power. You should not use one powerful transistor instead, because because of this, the operating frequency will decrease, and during welding work An unpleasant loud sound will appear. And incorrectly selected power can lead to the fact that very soon you will have to repair the equipment.
When assembling the welding inverter, maintain the required gaps between the windings and magnetic cores. Place PCB plates into the windings. This will increase the electrical safety of the welding machine and ensure its sufficient cooling.
Next, you need to attach the transformer to the base of the homemade welding inverter. Use 2-3 staples for this. Staples can be made from copper wire with a diameter of 3 mm. The boards are made of foil PCB. A material with a thickness of about 0.5-1 mm is suitable for this. Each board should have 4 narrow slots, which will reduce the load on the diode terminals.
After you have brought the toggle switch handle and LEDs to the front side, you will practically receive a ready-made reference device.
Place all assembled units of the unit on the base. It can be made from a getinax plate. A plate 0.5 cm thick will be enough. In its center you need to make a round window for the fan. Be sure to protect the latter with a grill. There must be an air gap between the magnetic cores.
Place LEDs and a toggle switch handle, as well as cable clamps and a variable resistor handle on the front side of the base. As a result, you will receive an almost finished welding machine. This structure must be placed in a casing made of textolite or vinyl plastic. The walls of the casing must have a thickness of 4 mm. Install the button on the electrode holder. It and the cable connected to it must be reliably insulated.
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Connecting a homemade welding machine
The finished welding inverter must be connected to the network or to a battery. Use clamps to connect to the battery. Be sure to observe polarity. The black clip goes to “-“, and the red one goes to “+”. If there is a connection between the battery and the on-board network of the unit, it does not need to be disconnected. When the outputs of the welding inverter are connected to the battery, a spark should appear.
Connect devices to an outlet. The outlet must have a fuse or an automatic shut-off feature. If necessary, an extension cord of up to 50 m can be used.
Turn on the implement button. If everything is normal, the green LED will light up. It will light green until the battery voltage goes beyond acceptable limits.
When connecting and using a homemade inverter, you need to take into account one more very important point. If, when operating the welding inverter on a load, the battery voltage drops to 10.5 W and continues to drop for more than 1 minute, the device will automatically turn off. This will prevent the battery from completely discharging and eliminate the need for repairs. Shorter voltage drops will not harm the welding machine, battery, or network.