The basis of the welding machine of the first design- laboratory transformer LATR for 9 A. The casing and all fittings are removed from it, only the winding remains on the core. In the transformer of the welding machine, it will be primary (network). This winding is insulated with two layers of electrical tape or varnished cloth. A secondary winding is wound over the insulation - 65 turns of wire or a set of wires with a total cross section of 12-13 mm 2. The winding is reinforced with electrical tape.The transformer is installed on an insulating stand made of textolite or getinaks inside a casing made of sheet steel or duralumin with a thickness of not more than 3 mm. In the cover of the casing, on the back and side walls, holes are made with a diameter of 8-10 mm for ventilation. From above, a handle made of a steel bar is strengthened.
An indicator light, a 220 V, 9 A switch and secondary winding terminals are brought to the front panel - a cable with an electrode holder is connected to one of them, a cable is connected to the other, the second end of which is pressed against the workpiece during welding. In addition, this last terminal must be grounded during operation. indicator light alternating current type SN-1, SN-2, M.N-5 indicates the device is turned on.
The electrodes for this apparatus must have a diameter of no more than 1.5 mm.
For welding machine of the second design(Fig. 126) it is necessary to make a transformer. From the W-shaped transformer iron, a core with a cross section of about 45 cm 2 is collected, the primary (mains) winding is wound on it - 220 turns of PEL wire 1.5 mm. Branches are made from the 190th and 205th turns, after which the winding is insulated with two or three layers of electrical tape or varnished cloth.
The secondary winding is wound over the insulated primary winding.
It contains 65 turns of wire or a set of wires with a total cross section of 25-35 mm 2. In the set, it is best to use wires of the PEL or PEV type 1.0-1.5 mm. As in the first design, the finished transformer is fixed on an insulating stand and placed in a casing. The casing walls must be at least 30 mm away from the transformer. On the front panel, in addition to the light bulb, switch and terminals, a switch is output that regulates the current strength.
In a welding machine of this design, electrodes with a diameter of 1.5 and 2 mm can be used.
You must wear a mask while working. You cannot connect this unit to a home network, as it consumes about 3 kW. You can use the device in the workshop if available electrical network, to which it is allowed to connect devices with a power of up to 5 kW.
Attention! Check grounding before starting work.
Wear dry tarpaulin overalls and gloves while welding. Place a rubber mat under your feet. Don't work without a mask.
I am sure: not a single artisan, homely owner will refuse from a compact and at the same time quite reliable, cheap and easy to manufacture “welder”. Especially if he finds out that this apparatus is based on an easily upgradeable 9-ampere (familiar to almost everyone from school physics lessons) laboratory autotransformer LATR2 and a self-made thyristor mini-regulator with a rectifier bridge. They allow not only to safely connect to a 220 V AC household lighting network, but also to change u on the electrode, which means choosing the desired welding current value.
Operating modes are set using a potentiometer. Together with capacitors C2 and C3, it forms phase-shifting chains, each of which, triggering during its half period. opens the corresponding thyristor for a certain period of time. As a result, adjustable 20-215 V are found on the primary winding of the welding T1. Transforming in the secondary winding, the required -u make it easy to ignite the arc for welding on alternating (terminals X2, X3) or rectified (X4, X5) current.
Resistors R2 and R3 shunt the control circuits of thyristors VS1 and VS2. Capacitors C1. C2 is reduced to an acceptable level of radio interference accompanying the arc discharge. In the role of the light indicator HL1, signaling the inclusion of the device in the household electrical network, a neon light bulb with a current-limiting resistor R1 is used.
To connect the "welder" to the apartment wiring, a conventional plug X1 is applicable. But it is better to use a more powerful electrical connector, which is commonly called "Euro plug-Euro socket". And as the SB1 switch, the VP25 "bag" is suitable, designed for a current of 25 A and allowing you to open both wires at once.
As practice shows, it does not make sense to install any kind of fuses (anti-overload machines) on the welding machine. Here you have to deal with such currents, if exceeded, the protection at the network input to the apartment will definitely work.
For the manufacture of the secondary winding, the casing-enclosure, the current collector slider and the mounting fittings are removed from the base LATR2. Then, on the existing winding 250 V (outlets 127 and 220 V remain unclaimed) impose reliable insulation(for example, from varnished cloth), on top of which a secondary (lowering) winding is placed. And this is 70 turns of an insulated copper or aluminum bus, having a diameter of 25 mm2. It is acceptable to make the secondary winding from several parallel wires with the same overall cross section.
Winding is more convenient to carry out together. While one, trying not to damage the insulation of adjacent turns, carefully stretches and lays the wire, the other holds the free end of the future winding, preventing it from twisting.
The upgraded LATR2 is placed in a protective metal casing with ventilation holes, on which there is a circuit board made of 10 mm getinax or fiberglass with a package switch SВ1, a thyristor voltage regulator (with resistor R6), an indicator light HL1 for turning on the device in the network and output terminals for welding on alternating (X2, X3) or constant (X4, X5) current.
In the absence of a basic LATR2, it can be replaced with a home-made "welder" with a magnetic circuit made of transformer steel (core cross section 45-50 cm2). Its primary winding should contain 250 turns of PEV2 wire with a diameter of 1.5 mm. The secondary one is no different from the one used in the modernized LATR2.
At the output of the low-voltage winding, a rectifier unit with power diodes VD3 - VD10 is installed for welding on DC. In addition to these valves, more powerful analogues are quite acceptable, for example, D122-32-1 (rectified current - up to 32 A).
Power diodes and thyristors are installed on radiators-heat sinks, the area of each of which is at least 25 cm2. The axis of the adjusting resistor R6 is brought out of the casing. A scale with divisions corresponding to specific values of direct and alternating voltage is placed under the handle. And next to it is a table of the dependence of the welding current on the voltage on the secondary winding of the transformer and on the diameter of the welding electrode (0.8-1.5 mm).
Welding transformer based on the widespread LATR2 (a), its connection to the main wiring diagram a home-made adjustable apparatus for welding on alternating or direct current (b) and a voltage diagram (c), explaining the operation of the resistor controller for the electric arc burning mode.
Of course, self-made electrodes made of carbon steel "wire rod" with a diameter of 0.5-1.2 mm are also acceptable. Workpieces with a length of 250-350 mm cover liquid glass- with a mixture of silicate glue and crushed chalk, leaving unprotected the 40 mm ends necessary for connecting to the welding machine. The coating is thoroughly dried, otherwise it will begin to “shoot” during welding.
Although both alternating (terminals X2, X3) and direct (X4, X5) current can be used for welding, the second option, according to welders, is preferable to the first. Moreover, polarity plays an important role. In particular, when a "plus" is applied to the "mass" (the object to be welded) and, accordingly, the electrode is connected to the terminal with a "minus" sign, the so-called direct polarity takes place. It is characterized by the release of more heat than with reverse polarity, when the electrode is connected to the positive terminal of the rectifier, and the “mass” to the negative. Reverse polarity is used if it is necessary to reduce heat generation, for example, when welding thin sheets metal. Almost all the energy released by the electric arc goes to the formation of a weld, and therefore the depth of penetration is 40-50 percent greater than with a current of the same magnitude, but with direct polarity.
And a few other very important features. An increase in the arc current at a constant welding speed leads to an increase in the penetration depth. Moreover, if the work is carried out on alternating current, then the last of these parameters becomes 15-20 percent less than when using direct current of reverse polarity. The welding voltage has little effect on the depth of penetration. On the other hand, the width of the seam depends on us: with increasing stress, it increases.
Hence an important conclusion for those involved in, say, welding work during body repair passenger car sheet steel: best results will give DC welding of reverse polarity at a minimum (but sufficient for stable arcing) voltage.
The arc must be kept as short as possible, the electrode is then consumed evenly, and the penetration depth of the welded metal is maximum. The seam itself is clean and strong, practically devoid of slag inclusions. And from rare splashes of the melt, which are difficult to remove after the product has cooled, you can protect yourself by rubbing the near-weld surface with chalk (the drops will roll off without sticking to the metal).
The arc excitation is carried out (after having previously supplied the corresponding Ucv to the electrode and the “mass”) in two ways. The essence of the first is in a light touch of the electrode on the parts to be welded, followed by its removal by 2-4 mm to the side. The second method is reminiscent of striking a match on a box: sliding the electrode over the surface to be welded, it is immediately taken away for a short distance. In any case, you need to catch the moment of the arc and only then, smoothly moving the electrode over the seam formed right there, maintain its calm burning.
Depending on the type and thickness of the metal to be welded, one or another electrode is selected. If, for example, there is a standard assortment for a St3 sheet 1 mm thick, electrodes with a diameter of 0.8-1 mm are suitable (this is what the design under consideration is mainly designed for). For welding work on 2 mm rolled steel, it is desirable to have both a more powerful “welder” and a thicker electrode (2-3 mm).
For welding jewelry made of gold, silver, cupronickel, it is better to use a refractory electrode (for example, tungsten). Metals that are less resistant to oxidation can also be welded using carbon dioxide protection.
In any case, work can be performed both with a vertically located electrode, and tilted forward or backward. But sophisticated professionals say: when welding with a forward angle (meaning sharp corner between the electrode and the finished seam) provides a more complete penetration and a smaller width of the seam itself. Backward welding is recommended only for lap joints, especially when dealing with profiled steel (angle, I-beam and channel).
An important thing is the welding cable. For the device in question, it is impossible better fit stranded copper (total cross section approx. 20 mm2) with rubber insulation. The required quantity is two one and a half meter segments, each of which should be equipped with a carefully crimped and soldered terminal lug for connection to the "welder". For a direct connection to the “ground”, a powerful crocodile clip is used, and with an electrode, a holder resembling a three-pronged fork is used. You can also use the car "cigarette lighter".
When building or repairing appliances or household appliances, quite often there is a need for welding of any elements. To connect the parts, you will need to use a welding machine. Today, you can easily purchase a similar design, but you should know that home-made welding machines can also be made.
Welding machines are of direct and alternating current. The latter are used in order to weld workpieces made of metal of small thickness at low currents. The arc of DC welding is more stable, while it is possible to weld in direct and reverse polarity. In this case, you can use an electrode wire without coating or electrodes. To give stability to the burning of the arc, at low currents it is recommended to make an overvoltage idle move welding windings.
To rectify alternating current, ordinary bridge rectifiers on large semiconductors with cooling radiators should be used. In order to smooth out voltage ripples, one of the leads must be connected to the electrode holder through a special choke, which is a coil of several tens of turns of a 35 mm copper bus bar. Such a bus can be wound on any core, it is best to use a core from a magnetic starter.
To rectify and smoothly regulate the welding current, you should use more complex schemes using large thyristors for control.
The advantages of constant current regulators include their versatility. They have a wide range of voltage configurations, and therefore such elements can be used not only to gradually adjust the current, but also to charge batteries, power electrical elements for heating and other circuits.
AC welding machines can be used to connect workpieces with electrodes whose diameter is more than 1.6 mm. The thickness of the connected workpieces can be more than 1.5 mm. In this case, there is a large welding current, and the arc burns stably. Electrodes that are made for welding exclusively on alternating current can be used.
Stable arc burning can be obtained if the welding fixture has a falling external characteristic, which determines the relationship between current and voltage in the welding chain.
What should be considered in the process of manufacturing welding machines?
For stepwise overlapping of the spectrum of welding currents, switching of both primary and secondary windings is necessary. For a smooth current configuration within the selected spectrum, use mechanical properties winding movement. If you remove the welding winding in relation to the network winding, the leakage magnetic fluxes will increase. It should be understood that this can lead to a decrease in welding current. In the process of manufacturing homemade design for welding, it is not necessary to strive for a complete overlap of the spectrum of welding currents. It is recommended to first assemble to work with electrodes 2-4 mm. If necessary in the future to work on small welding currents, the design can be supplemented with a separate straightening device with gradual adjustment of the welding current.
Homemade designs must satisfy some requirements, the main of which are the following:
- Relatively compact and light weight. Such parameters can be reduced by reducing the power of the structure.
- Sufficient duration of operation from the mains 220 V. It can be increased by using steel with high magnetic permeability of heat-resistant wire insulation for winding.
Such requirements can be easily met if you know the basics of the construction of welding structures and adhere to the technology of their manufacture.
Back to index
How to choose the type of core for the manufactured structure?
In the process of manufacturing such structures, rod magnetic wires are used, they are more technologically advanced. The core is assembled from electrical steel plates of any configuration, the thickness of the material should be 0.35-0.55 mm. The elements will need to be pulled together with studs that are covered with insulating material.
In the process of choosing the core, the dimensions of the "window" should be taken into account. Windings of elements should be placed in the design. It is not recommended to use cores with a cross section of 25-35 mm, since in this case the manufactured structure will not have the necessary power reserve, as a result of which it will be quite difficult to produce high-quality welding. In this case, overheating of the device cannot be ruled out either. The core should be a section of 45-55 mm.
In some cases, welding structures with toroidal cores are produced. These devices have higher electrical performance and low power losses. It is much more difficult to make such devices, since the windings will need to be placed on the torus. You should know that winding in this case is quite difficult to perform.
The cores are made of strip transformer iron, which is rolled into a torus-shaped roll.
To increase the internal diameter of the torus, with inside you need to unwind part of the metal tape, and then wind it on the outside of the core.
Back to index
How to choose the right winding design?
For the primary winding, it is recommended to use copper wire, which is covered with fiberglass insulating material. You can also use wires that are covered with rubber. Do not use cords that are covered with PVC insulation.
A large number of taps of the network winding is not recommended. By reducing the number of turns of the primary winding, the power of the welding machine will increase. This will lead to an increase in the arc voltage and a deterioration in the quality of the connection of the workpieces. By changing the number of turns of the primary winding, it will not be possible to achieve overlapping of the welding current spectrum without deteriorating the welding properties. To do this, it will be necessary to provide for switching turns of the secondary welding winding.
The secondary winding should contain 67-70 turns of a copper bar with a cross section of 35 mm. You can use a stranded network cable or a flexible stranded cord. insulating material must be heat resistant and reliable.
Back to index
Homemade autotransformer welding machine
The welding device is powered by 220 V. The design has excellent electrical performance. Thanks to the use of a new form of magnetic wire, the weight of the fixture is about 9 kg with dimensions of 150x125 mm. This is achieved by using a band of iron, which is rolled into a torus-shaped roll. In most cases, a standard record package is used. W-shape. The electrical performance of the transformer structure on a magnetic wire is approximately 5 times higher than that of similar plates. Power loss will be minimal.
Elements that will be needed in order to make a welding machine with your own hands:
- magnetic wire;
- autotransformer;
- electric cardboard or lacquer cloth;
- wires;
- wooden lath;
- insulating material;
- transformer;
- cable;
- casing;
- switch.
An excellent welding machine can be made on the basis of the LATR laboratory autotransformer and a home-made thyristor mini-regulator with a rectifier bridge. They make it possible not only to safely connect to a standard 220 V network, but also to change the voltage on the electrode, which means choosing the required welding current.
A toroidal autotransformer (ATR) is placed inside the housing, made on a large-section magnetic circuit. It is this core-magnetic circuit that will be needed from LATR for the manufacture of a new welding transformer (ST).
We need two identical magnetic circuit rings from large LATRs. LATRs were produced in the USSR different types with a maximum current from 2 to 10 A. A welding transformer for its manufacture is suitable for those whose magnetic core sizes will make it possible to place required amount turns. The most common among them is the ATR type LATR 1M.
The magnetic circuit from LATR 1M has the following dimensions: outer diameter 127 mm; internal 70 mm; ring height 95 mm; cross section 27 cm2 and weight 6 kg. From two rings from this LATR, you can make an excellent welding transformer.
For many ATRs, the magnetic circuit has a larger outer diameter of the ring, but a smaller height and window diameter. In this case, it must be increased to 70 mm. The ring of the magnetic circuit is made of pieces of iron tape wound on top of each other, welded along the edges.
In order to adjust the inner diameter of the window, it is necessary to disconnect the end of the tape from the inside and unwind the required amount. Don't try to do it all at once.
Welding transformer the beginning of the manufacturing operation, firstly it is required to isolate both rings. Paying attention to the corners of the edges of the rings, if they are sharp, they can easily damage the applied insulation, and then close the winding wire. At the corners, it is better to glue some kind of elastic tape or a cambric cut along. From above, the ring is wrapped with a small layer of insulation. Next, the insulated rings are fastened together.
The rings are tightly twisted with a dense tape, and fixed on the sides with pegs tied with electrical tape. Now the core for the CT is ready.
Let's move on to the next item manufacturing of a welding transformer, namely the laying of the primary winding.
Welding winding transformer - wound as shown in figure three - the primary winding is in the middle, both sections of the secondary are placed on the side arms. The primary winding requires about 70-80 meters of wire, which will have to be pulled through both windows of the magnetic circuit with each turn. In this case, I can recommend using the device shown in Figure 4. First, the wire is wound on it and in this form it is easily pulled through the windows of the rings. The winding wire can be lumpy, about ten meters, but it is still better to use a whole one.
In this case, it is wound in parts, and the ends are fastened without twisting and soldered together, and then isolated. The diameter of the wire used in the primary winding is 1.6-2.2 mm. in the amount of 180-200 turns.
Let's start winding ST. We attach the cambric to the end of the wire with electrical tape to the beginning of the first layer. The surface of the magnetic circuit is rounded, so the first layers will have fewer turns than each subsequent layer to level the surface, see Figure 5. The wire must be laid turn to turn, in no case should the wire be overwhelmed on the wire.
Wire layers need to be isolated from each other. To save space, the winding should be laid as compactly as possible. On a magnetic circuit of small rings, the interlayer insulation must be applied thinner, for example, using ordinary adhesive tape. Do not rush to wind the primary winding once. It is easier to do this in 2-3 approaches.
Let's determine the number of turns of the secondary winding of the ST for the required voltage. To begin with, we connect the already wound primary winding to AC voltage at 220 volts. The idling current of this variant of the ST is low - only 70-150 mA, the hum of the ST should be quiet. Wind 10 turns of wire on one of the side arms and measure the output voltage on it with a voltmeter. Each of the side arms receives only half of the magnetic flux generated on the central arm, so here, 0.6-0.7 V will fall on each turn of the secondary winding. Based on the result, we calculate the required number of turns in the secondary winding, focusing on the voltage level at 50 volts, usually about 75 turns. The easiest way is to wind with 10 mm2 stranded wire in synthetic insulation. It is possible to assemble the secondary winding from several strands of copper wire. Half of the turns should be wound on one shoulder, half on the other.
Having wound the windings on both arms of the ST, you need to check the voltage on each of them, a difference of 2-3 volts is allowed, but no more. Then the windings on the shoulders are connected in series, but so that they are not in antiphase, otherwise the output will be near zero.
With a standard mains voltage, a welding transformer on a magnetic circuit made of LATR can deliver current in arc mode up to 100-130 A, with a short circuit, the current of the secondary circuit reaches 180 A.
The arc strikes very easily at XX voltages of about 50 V or higher, although the arc can be struck at lower voltages without much difficulty. On rings from LATRs, you can also assemble ST according to a toroidal scheme.
This will also require two rings, better from large LATRs. The rings are connected and insulated: one large ring-magnetic circuit is obtained. The primary winding contains the same number of turns as described above, but it is already wound around the entire ring and usually in two layers. It is necessary to isolate the layers with as thin materials as possible. Do not use thick winding wires.
The advantage of the CT toroidal scheme is its high efficiency. There is 1 volt of voltage for each turn of the secondary winding, therefore, the secondary winding will contain fewer turns and the output power will be higher than in the previous case.
The obvious disadvantages include the problem with winding, the limited volume of the window and the inability to use large diameter wire.
It is problematic to use hard wires for the secondary. It is better to use soft stranded
The arc burning characteristic of the toroidal CT is an order of magnitude higher than that of the previous version.
Scheme of a welding machine based on ST on a magnetic circuit from Latrov |
Operating modes are set to potentiometers. Together with capacitances C2 and C3, it forms classical phase-shifting chains, each of which will operate in its own half-cycle and open its thyristor for a given period of time. As a result, adjustable 20 - 215 V will be on the primary winding of the ST. Transforming in the secondary winding, they easily ignite the arc for welding on alternating or rectified current into the desired voltage.
For the manufacture of a welding transformer, you can use a stator from an asynchronous motor. The size of the core is determined in this case by the cross-sectional area of the stator, which must be at least 20 cm 2 .
In domestic color TVs, large, heavy network transformers were used, for example, TS-270, TS-310, ST-270. They have U-shaped magnetic cores, they are easy to disassemble by unscrewing just two nuts on the tightening studs, and the magnetic circuit breaks into two halves. For older transformers TS-270, TS-310, the cross section of the magnetic circuit has dimensions of 2x5 cm, S = 10 cm2, and for newer transformers - TS-270, the cross section of the magnetopropod S = 11.25 cm2 with dimensions of 2.5x4.5 cm. In this case, the window width of older transformers is several millimeters larger. Older transformers are wound with copper wire, from their primary windings a wire can come in handy.
Welding transformer other possible types and designs |
ST, in addition to special production, can be obtained by converting ready-made transformers for various purposes. Powerful transformers of a suitable type are used to create networks with a voltage of 36, 40 V, usually in places with increased fire hazard, humidity and for other needs. For these purposes, use different types transformers: different capacities included in 220, 380 V in a single or three-phase circuit.
When designing or repairing appliances, household equipment, a problem often arises: how to weld certain parts. Buying a welding machine is not quite easy, but making it yourself ...
In this article, you can get acquainted with a simple home-made welding machine made according to the original scheme.
Welding machine works from a network of 220 V and possesses high electrotechnical characteristics. Thanks to the use of a new form of magnetic circuit, the weight of the device is only 9 kg with overall dimensions 125 x 150 mm. This is achieved by using a torus-shaped transformer strip iron instead of the traditional W-shaped plate pack. The electrical characteristics of the transformer on the magnetic circuit are about 5 times higher than those of the Ш-shaped one, and the electrical losses are minimal.
To get rid of the search for scarce transformer iron, you can purchase a ready-made LATR for 9 A or use a magnetic circuit from a burned-out laboratory transformer. To do this, remove the fence, fittings and remove the burnt winding. The released magnetic circuit must be isolated from future winding layers with electric cardboard or two layers of varnished cloth.
The welding transformer has two independent windings. In the primary, a PEV-2 wire of 1.2 mm, 170 m long, was used. For convenience, you can use a shuttle (a wooden lath 50 x 50 mm with slots at the ends), on which the entire wire is pre-wound. A layer of insulation is placed between the windings. The secondary winding - copper wire in cotton or glassy insulation - has 45 turns over the primary. Inside the wire, turn to turn is placed, and on the outside with a small gap - for uniform arrangement and better cooling.
It is more convenient to do the work together: one carefully, without touching adjacent turns, so as not to damage the insulation, pulls and lays the wire, and the assistant holds the free end, preventing it from twisting. A welding transformer made in this way will give a current of 50 - 185 A.
If you purchased a "Latr" for 9 A and upon examination it turned out that its winding was intact, then the matter is greatly simplified. Using the finished winding as the primary, it is possible to assemble a welding transformer in 1 hour, giving a current of 70 - 150 A. To do this, remove the guard, current-collecting slider and mounting hardware. Then identify and mark the leads for 220 V, and securely insulate the remaining ends, temporarily press them against the magnetic circuit so as not to damage them when working with the secondary winding. The installation of the latter is carried out in the same way as in the previous version, while using a copper wire of the same cross section and length.
The assembled transformer is placed on an insulated platform in the former casing, having previously drilled ventilation holes in it. The wires of the primary winding are connected to the 220 V network with a SHRPS or VRP cable. A disconnect circuit breaker must be provided in the circuit.
The conclusions of the secondary winding are connected to flexible insulated wires of the PRG, an electrode holder is attached to one of them, and the workpiece to be welded to the other. The same wire is grounded for the safety of the welder.
The current regulation is provided by the inclusion in series in the wire circuit of the electrode holder of the ballast - nichrome or constantan wire with a diameter of 3 mm and a length of 5 m, coiled with a snake, which is attached to asbestos-cement sheet. All wire and ballast connections are made with M10 bolts. Using the selection method, moving the point of attachment of the wire along the snake, the required current is set. It is possible to adjust the current using electrodes of different diameters. For welding, electrodes of the type with a diameter of 1 - 3 mm are used.
All necessary materials for a welding transformer can be purchased from the distribution network. And for a person familiar with electrical engineering, making such an apparatus is not difficult.
When working, in order to avoid burns, it is necessary to use a fiber protective shield equipped with a light filter E-1, E-2. Headgear, overalls and gloves are also required. The welding machine must be protected from moisture and not allowed to overheat. Approximate mode of operation with an electrode with a diameter of 3 mm: for a transformer with a current of 50 - 185 A - 10 electrodes, and with a current of 70 - 150 A - 3 electrodes, after which the device must be disconnected from the mains for at least 5 minutes.
