We do resistance welding from the microwave with our own hands. How to make a spot welding machine from a conventional microwave What is the power of the microwave power transformer

In your home, there is often a need to use a welding machine. Buying a ready-made unit will significantly affect the family budget. A way out can be found by making a welding machine from an old microwave oven with your own hands.

Financial costs are minimal, and the possibilities are quite sufficient to solve household problems. The main thing is that the microwave oven transformer is in working order. It is this microwave unit that can provide a stable supply of electricity for welding metal parts.

An unnecessary microwave oven can be easily found among friends, neighbors, among your own old trash. Our people are accustomed to keeping used equipment just in case, in order to build something out of it with their own hands.

A small microwave oven is enough. In most cases, a power of 800-650 watts is enough. If the microwave power values are higher, the capabilities of the welding machine will increase.

The transformer has two different windings. One is primary, has a larger number of turns, is used when connected to a centralized electricity supply network.

The other winding - the secondary - has fewer turns. To make a welding machine with your own hands, it is not needed. The task of the craftsman is to carefully remove it from the microwave transformer.

In order not to damage the primary winding, which is located very close to the secondary, it is possible to lay and fix a metal plate or a ruler between them.

After that, the unnecessary part can be cut with a hacksaw without fear of damaging the turns of the primary winding. You can very carefully cut off everything unnecessary with a chisel. Be careful with your hand efforts so as not to damage the microwave units that you want to save for the welding machine.

Repeat the procedure on the other side, carefully removing the filament winding. After cutting, all the wires of the secondary winding must be pulled out of the transformer housing until both niches are completely released. Simplifies the cleaning of the microwave transformer by drilling out all the excess with a drill.

Sometimes the windings are very close to each other. You can carefully remove them only by disassembling the core, and then re-gluing them with your own hands.

New winding

In the resulting niches, a new secondary winding is made of large-diameter enameled or copper wire. The minimum section size should be 1 cm.

The wires may not be solid, but stranded. An important indicator for a microwave welding machine is the total diameter of the wires. They need to be laid tightly, leaving no gaps.

The exact size of the section and the required number of turns can be calculated from special tables or using online calculators, focusing on the dimensions of the core and the required output power. Some craftsmen select empirically. At the ends of the winding, the tips should be well fixed.

The transformer removed from the microwave is ready for use in a new capacity. He will be able to supply current, the strength of which reaches 1000 A, which is quite enough for a home unit. The main part for contact welding is made by hand from an old microwave oven.

If you need a more powerful welding machine, you will have to redo two transformers. The connection of two transforming blocks is carried out in series.

It is important to connect the windings of the same name, otherwise a short circuit will occur. The correctness of the action is checked by markings or using a voltmeter. When both microwave transformers are connected, the current strength should be checked.

It should not exceed 2000 A. Large values will overload the home electrical network, and the welding machine will either not work at all or will burn through the metal.

Case manufacturing

There are several options for manufacturing a housing for a welding machine. Some craftsmen make the case out of wood. However, it is most convenient to use welding from a transformer from a microwave oven if you place the device in a housing from system block computer. Finding an old "system unit" is easy. They also accumulate in many homes when replacing obsolete appliances with new models.

Legs are screwed onto a fragment of the body with ventilation holes from below. You can take the support legs from an unnecessary VCR, player, or any other equipment.

A window should be cut out in the side part of the body of the welding machine, closed with a dielectric plate made of any heat-resistant insulating material. Due to the fact that the terminals on the plate will heat up, melting of the plate should be avoided.

Using a computer case is convenient for several reasons:

it has an on and off button;
on the case there is a ready-made socket for connecting to the network, to which it remains only to connect the converted transformer from the microwave oven;
ventilation cells provide effective cooling of the contents of the case. The fan can also be taken from an old PC;
the design has a decent appearance.

It makes sense to install LED indication on the heat-insulating plate. This will help you easily see the condition of the welding machine.

Choice of electrodes

For right choice resistance welding electrodes, it is useful to look at GOSTs, which specify all the required parameters. Convenient access to the place of the future seam is provided by straight electrodes. The diameter of the copper rods cannot be less than the diameter of the working wires.

The connection is best made by soldering. This will reduce the chance of oxidation during operation. Due to the fact that the electrodes are inevitably consumed during welding, they must be sharpened in a timely manner.

Ideally, the electrode ends should be in the shape of a sharpened pencil. The result of working on a microwave oven after gaining some experience will be indistinguishable from factory resistance welding.

Important optional devices

To obtain a good seam, the process must be skillfully controlled. The system for turning on the welding machine can be used from the old system unit.

For convenience when working, you will need good levers of optimal length, which will help to hold the part and press it. It is easy to mount the lever mechanism on the screws.

If it is placed on the lever itself, the master will have the possibility of additional manipulations, the second hand will be freed when working with the welding machine.

For home welding, not very large clamping forces are sufficient. For thick sheet steel, a do-it-yourself welding machine will not work for many reasons. In particular, the capabilities of microwave transformers are not enough for this.

If you need to weld at several points, a lever having a length of about 60 cm is quite enough. This will save the physical burden of the master. The pressure on the working point will be 10 times greater than the force applied by the welder.

To ensure a static position of the device from the microwave, you need to firmly fix it on the work surface with the help of clamps.

Good welding occurs when the electrodes come into contact with the workpiece for a strictly defined time, which can be visually determined with experience. If you cannot rely on experience, it makes sense to mount a special relay.

During the entire period of operation, a welding machine made from a microwave oven must be well cooled by one or more fans. In addition, it is always useful to pause in work, allowing the equipment to cool down and the master to rest.

Spot welding, as you know, is performed on specialized equipment, however, such a device can not only be found in a serial version, but also do it yourself: a transformer removed from an old microwave oven is useful for this. The resulting device will give you the opportunity to perform high-quality spot welding using alternating current, the strength of which is not regulated.

The transformer is the most important element of any such spot welding device: its task is to increase the input voltage to the required value. To cope effectively with this, the device must have a high transformation ratio. Large microwave ovens are equipped with such transformers, one of which you need to find. When you find such a microwave model, you will need to very carefully remove the transformer from it.

The assembly technology of the spot welding machine can be seen in more or less detail in the video below. An example of this homemade device will help us illustrate the process of creating a dot. For more detailed information about the details of the assembly, read the article in full.

Removing the transformer from the microwave

If a transformer with a power of 700–800 W is used in a home-made spot welding machine, then with its help you can connect metal sheets with a thickness of up to 1 mm. Such a transformer is included in the category of step-up devices; to provide power to the magnetron, it is capable of generating a voltage of 4 kV.

The magnetron, which any microwave oven is equipped with, requires high voltage for its operation. In this regard, the transformer connected to it is distinguished by a smaller number of turns on its primary winding and a large number on the secondary. At the latter, a voltage of the order of 2 kV is created, which then doubles due to the use of a special doubler. It makes no sense to check the performance of such a device by measuring the voltage connected to its primary winding.

Carefully remove the transformer from the microwave. Do not pick up a hammer or other heavy objects. Its base is unscrewed from the microwave, all fasteners are removed, and the transformer is carefully removed from its installation site. In the device removed from the microwave oven, you will need, firstly, its magnetic circuit, and secondly, the primary winding, which, compared to the secondary, is made of thicker wire and has fewer turns.

Because of its uselessness, you will have to dismantle the secondary winding, for which a hammer and a chisel will already come in handy. It is very important not to damage or crush the primary winding, so you need to act with the utmost care. If, when dismantling the secondary winding, you find shunts in the transformer used to limit the current strength, they must also be removed.

The secondary winding can be cut with a chisel

If the magnetic circuit of the transformer is not glued, but a welded structure, then it is better to remove the secondary winding from it using a chisel or an ordinary hacksaw. If the winding is very tightly stuffed into the window of the magnetic circuit, then, having cut the wires, it will be necessary to drill or pick it out. This must be done very carefully, since the magnetic circuit can collapse due to such manipulations.

After dismantling, a new secondary winding should be wound. To do this, you will need a wire with a diameter of at least 1 cm. If you do not have such a wire in stock, you will have to buy it. In this case, it is not at all necessary to purchase a solid stranded wire of such a cross section; a bundle of several individual conductors can also be used, which in total will provide the required diameter. After installing a new secondary winding, your upgraded transformer will be able to generate current up to 1000 A.

If you want to make the spot welding machine more powerful, then the technical capabilities of one transformer may not be enough for you. Here it is necessary to use two such devices (respectively, having disassembled two microwave ovens).

The subtleties of upgrading a transformer from a microwave oven

To make a secondary winding, you need to wind 2-3 turns on the core, which will provide an output voltage of about 2 V, and a short-term welding current of more than 800 A. This is quite enough for effective work spot welding machine. Winding this many turns can be difficult if the wire used has a thick layer of insulation. Solving this problem is quite simple: you need to remove the standard insulation from the wire and wrap it with electrical tape that has a fabric base. It is very important that the wire used for the secondary winding has the minimum possible length, which will avoid an unreasonable increase in its resistance and, accordingly, a decrease in the current strength.

If you need to weld metal sheets up to 5 mm thick, keep in mind that this will require a spot welding machine with more power. To make it yourself, you need to use two transformers connected in one circuit. It is imperative to follow the relevant rules when making such a connection. If you make a mistake and incorrectly connect the primary and secondary terminals of the two transformers, a short circuit may occur. The correctness of the connection of the windings, if there is no marking on their terminals of the same name, is checked using a voltmeter.

After the correct connection of the terminals of the same name of the two transformers, it is required to measure the value of the current strength, which they jointly form. As a rule, home-made transformers designed for spot welding machines, which are planned to be operated in home workshops, are limited in current strength - no more than 2000 A. Exceeding this value will provoke interruptions in the electrical network not only in your home, but also in your closest neighbors . And this, of course, will lead to conflicts. The value of the current supplied by the connected transformers, as well as the presence short circuit in their circuit is checked with an ammeter.

Another example of a spot welding assembly is shown in the video below:

What results can be achieved if, in accordance with the rules, two transformers are connected that do not differ big power? If we take two identical devices with the following characteristics: power - 0.5 kW, input voltage - 220 V, output voltage - 2 V, rated current - 250 A, then by connecting their primary and secondary windings in series, at the output you will get twice the rated current, i.e. 500 A.

The short-term welding current will also increase in almost the same way, but significant losses will be observed during its formation, which is due to the high resistance of such electrical circuit. Both ends of the secondary winding - wires Ø 1 cm - are connected to the electrodes of the spot welding machine.

Connection of 2 transformers according to scheme No. 1

If you have two powerful transformers at your disposal, but their output voltage is not enough for a home-made device, you can connect their secondary windings in series, which should have the same number of turns. Such a measure is resorted to if it is impossible to simply wind the turns on the secondary winding due to the insufficiently large size of the window on the magnetic circuit.

With such a connection, it is necessary to ensure that the direction of the turns on the secondary windings of the connected devices is consistent, otherwise antiphase may occur, and the output voltage of such a combined device will be close to zero. To experimentally determine the correct connection, it is desirable to use thin wires.

How to determine the same-name conclusions of transformers

If the terminals of the windings of the connected devices are not marked, then it is necessary to determine among them the names of the same name in order to connect them together. This problem can be solved in the following way: the primary and secondary windings of two or more transformers are connected in series, a voltage is applied to the input of such a combined device, and an AC voltage voltmeter is connected to the output terminals (terminals from the secondary windings connected in series).

Depending on the direction of connection, the voltmeter may behave differently:

show one or another voltage value;
show no voltage at all in the circuit.

If the voltmeter produces any voltage, then there are opposite conclusions in the connection circuit of both the primary and secondary windings. When connecting the windings in such a way the wrong way the following processes take place in them: the voltage supplied to the input of the primary windings of two connected transformers decreases by half on each of them; the increase in voltage occurs on the secondary windings, each of which has the same transformation ratio. The output voltmeter will register the total voltage, the value of which is equal to twice the input value.

If the voltmeter shows the value "0", then this means that the voltages coming out of each of the series-connected secondary windings are equal in value, but have different signs so they cancel each other out. In other words, at least one of the pairs of windings connected in a circuit is connected by terminals of the same name. In this case, the correct connection of the circuit elements is achieved by changing the order of connecting the primary or secondary windings, focusing on the readings of the voltmeter.

Electrodes for homemade spot welding

When choosing electrodes for a spot welding machine assembled from a microwave oven with your own hands, you should pay attention to ensuring that their diameter matches the diameter of the wire to which they are connected. Copper rods can be used as such elements, and tips from professional soldering irons are suitable for low-power devices.

During operation, electrodes for spot welding actively wear out. To correct their geometric parameters, they must be constantly undermined. Naturally, over time, such elements will require replacement with new ones.

The wires with which the electrodes are connected to the spot welding machine must be of a minimum length, otherwise significant power of the device will be lost in them. Power losses will become serious even if there are many connections in the electrical circuit "electrode - spot welding device". If you want to increase the efficiency of using your home-made equipment, then it is better to solder copper tips on the wires that connect the electrodes. Using such lugs, you will avoid power losses at the points of contact arising from the increased resistance of crimp or any other connections.

The wires connecting the electrodes to the spot welding machine have a fairly large diameter, so special tinned tips will help facilitate their soldering. Since the electrodes for such a device are removable, soldering is not performed at the points of their connection with the tips. Of course, in such places, constantly subject to oxidation, there is also a loss of power, but they are much easier to clean than swaged lugs.

We install the electrodes on the welding machine

As mentioned above, an electrode for resistance welding can be made from a copper bar or a tip from a professional soldering iron if the power of the device is low. The wire from the device is connected to the electrode using a copper tip, which is connected to it by soldering.

The tip is aligned with the electrode using a bolted connection, which must be very reliable so that an increase in resistance at the point of unreliable contact does not lead to a loss in power of the spot welding machine. To make such a connection, holes of the same diameter are made in the electrode and tip.

Bolts and nuts, with which the electrodes and lugs will be connected to wires, are best chosen from copper or its alloys, which are characterized by minimal electrical resistance. Elements of such connections, which greatly simplify the maintenance of the resistance welding machine, are not difficult to make with your own hands.

Homemade Spot Welding Controls

Controlling a spot welding machine (especially one made from a microwave oven with your own hands) is not particularly difficult. Two elements are enough for this: a lever and a switch. The compression force between the electrodes, for which the lever is responsible, must ensure reliable contact of the parts to be joined at the point of welding. To meet these important requirements, the lever mechanisms of such devices can be supplemented with screw elements, which provide an even greater compressive force. Naturally, such an element of a spot welding device must have a very high reliability.

On serious production equipment, which is used to connect sheets of steel of considerable thickness, compression elements are installed that create pressure from 50 to 1000 kg - depending on the need. And on spot welding machines used for irregular and simple work in a home workshop, it is quite enough that such a mechanism creates a pressure of up to 30 kg. For convenience and ease of use on the spot welding machine, its clamping lever is made longer, this will also increase the compression force to the required value.

For a homemade homemade device, a lever is enough, the length of which will be 60 cm. With such a lever, you can increase the applied force by 10 times. Accordingly, if you press on the lever with a force of 3 kg, then the electrodes and the parts to be connected will be compressed by a force of 30 kg. So that such a lever does not move the apparatus itself when pressed, the base of the equipment must be securely fixed on the surface of the desktop with a clamp.

The switch responsible in the device for supplying current to is connected to the circuit of the primary winding of the transformer, the current in which is much less than in the secondary. If you connect the switch to the secondary winding, then it will create additional resistance, and its contacts will be tightly welded under the influence of a strong current.

If a lever is used as a clamping mechanism, then it is better to place the switch directly on it, then the second hand will be free (it can be used to support the parts to be welded).

Features of working on home-made equipment for spot welding are that current should be applied to the electrodes only when they are in a compressed state. Otherwise, you will encounter intense sparking of the electrodes and, as a result, their active burning. You can get the initial experience of working on such a device with the help of a training video.

Electrodes of equipment for spot welding are actively heated during operation. In addition, the transformer and conductive elements of such a device are subject to intense heating. To avoid too much heat, which can lead to the failure of spot welding equipment, a simple cooling system should be provided. For this, a conventional fan is often used. You can also take breaks in work, necessary for cooling the elements of the apparatus.

The exposure time of electrodes under current in a compressed state during welding can be controlled visually, focusing on the color of the dot at the junction, or use a special relay for this.

It is obvious that it is not difficult to make a spot welding machine based on a microwave transformer, after carefully studying the presented videos and photos of the assembly process and taking into account the recommendations voiced.

(votes: 6 , average rating: 4,83 out of 5)

A microwave oven is now in almost every kitchen. Manufacturers are improving devices, equipping them with additional functions, endowing them with new features.
An aged oven model is sometimes simply thrown away. But you shouldn't do it! After all, its components will still serve in capable hands.

Ideas for using the microwave part

Copper wire on a coil, decorated with several rows of windings and metal plates, often remains operational even after the microwave is out of order. So it's too early to get rid of it.

We offer options for using a transformer from a microwave oven.

How to make a former transformer a power supply

Remove item from microwave.
Remove metal plates. To do this, you will need tools (screwdriver, chisel).

Advice. If you use a grinder, the work can be done easier. When doing this, care must be taken not to damage the windings.

Carefully remove 3 windings.
For the power supply, you will need one of the large ones, designed for 220 V. It is thicker than the other, but less wire is used.
Wind the desired winding on the coil.
Place the coil on the core, shaped like the letter W.
Make calculations for the second winding layer. This is done experimentally. Start with 10 turns on the core. Then voltage is applied through both windings and the data is measured on the one that consists of 10 turns. With an indicator equal to 10, you can continue to work. The final number of turns depends on how much power you need to get.
Fix the core.

The base of the power supply is ready. For its final production, you will need to arrange it in a special case and retrofit it with a diode bridge and a capacitor.

name this method simple work is hardly possible. However, as a result of the laborious process, you will get a powerful power supply, the acquisition of which would require significant funds.

Welding machine

Even small repairs in the house or on personal plot often requires welding.

If you have an unnecessary microwave, you can make your own convenient and reliable spot welding machine.

The transformer is taken out of the microwave.
Remove the existing secondary winding.
Make a new winding using a wire with a diameter of at least 10 mm.

Important. If you do not have a thick wire, you can replace it with several thinner wires. The main thing is that the sum of their diameters is 10 mm or more.

When working with thick wire, you can remove its thick insulating layer and replace it with electrical tape, one side of which has a fabric backing. In this case, the winding will be easier to do.
If you are working on a welding machine, keep in mind that it will be suitable for joining thin sheets of metal.
To weld thick plates and increase power, you will need a second transformer.

A spot welding machine can be bought today at any store, but its cost is sometimes high. What to do if the welding machine is required only for a certain type of work?

As a basis for manufacturing, you can use a transformer from an unnecessary microwave oven. Such spot welding from a trance from a microwave oven will be not only simple, but also of high quality. For assembly, apply simple tools, only the transformer itself is an expensive part. If there is no relevant experience in assembling such equipment, then it is best to prefer the finished version. But if you have the skills, you can easily avoid unnecessary expenses by assembling the device with your own hands.

To make a do-it-yourself welding contact machine for point-to-point connection of steel sheets, you will need the following tools and materials:

transformer from an old microwave oven (or 2 if welding with high power is required);
copper wire or bundle of wires;
clamping levers;
convenient lever with the required length;
base for the welding machine;
clamps;
screwdriver;
cables and winding for connecting individual elements;
copper electrodes of the required diameter and length.

The main element is the transformer. The case for such equipment may not be used, there is no great need for it. It is important to make levers of the required length, at the ends of which the electrodes will be strengthened. With the help of a special lever, the electrodes will close, when turned on, a current will pass through them, which ensures spot welding.

Transformer assembly

The main part of the contact welding machine is a transformer from an old microwave oven (Fig. 1). In this case, its power must be at least 1 kW. Such a transformer allows welding sheets of steel, the thickness of which is 1 mm. If more powerful equipment is needed, then 2 such transformers will be required.

Figure 1. Microwave transformer diagram.

From the transformer, a magnetic circuit is used, the primary winding. The secondary winding must be carefully cut down, and then selected with a rod. The shunts located on both sides are also removed. Next, you need to make a secondary winding, for this a stranded wire with a diameter of 10 cm² is used. If 2 transformers are used, it is necessary to combine them into one when creating the secondary winding. The conclusions of the windings are interconnected, it is impossible to make mistakes here. Next, you should provide for the installation of controls and the connection of electrodes. You will also need a durable case, you can borrow it from old household appliances. Pay attention to the approximate assembly diagram (Fig. 2).

Manufacturing of electrodes

For work, special electrodes are used that provide current to the welding point. They perform the function of a compressive element, serve to further remove heat. It is important to choose the right electrode type, shape, dimensions and other parameters. Today, curly or straight electrodes can be used. The latter are used most often, as they provide direct access to the welding point. The parameters of such electrodes fully comply with GOST 14111-90, which regulates the diameters for working rods: 10 mm, 13, 16, 20, 25, 32, 40 mm.

Figure 2. Scheme of assembly of the apparatus for welding.

When spot welding is planned, it is best to use copper rods, while their diameter should be equal to or greater than the diameter of the working wire. As you use the electrodes, you need to undermine, giving them the shape of a pencil tip, since during operation they grind down a lot. Over time, the electrode needs to be replaced, this should not be forgotten. Before starting work, the tips must be soldered to the wires, otherwise they will oxidize.

Management and process of welding

Resistance welding is a relatively simple process, although it is not always possible to obtain a sealed seam. The quality won't be that bad. However, in order for welding to be done correctly, you must first take care of the controls. AT this device, made on the basis of a microwave oven transformer, uses such simple controls as a switch and a lever. In this case, it is necessary to ensure the maximum compression force, since the quality of welding depends on it. The lever is best made longer, its quality must be high in order to ensure all working conditions. The base of the welding machine must be fixed to the work surface with clamps.

The force during welding is given not only by a lever, but also by a special lever-screw mechanism. There are other methods, but it is best to use these on your own. The control switch must be installed directly in the primary winding circuit, since a large current is observed in the secondary circuit, and the installed switch creates additional resistance. In such a situation, the contacts can be welded to each other tightly.

The clamping lever mechanism is mounted directly on the lever, in this case it turns out to be convenient to turn on the current and press the lever, without wasting time when welding.

The second hand can hold the details. A feature of using a welding machine is that it is possible to turn on the current only if the electrodes are compressed. If this condition is not met, then sparks appear. And this leads to the fact that the electrodes burn out, become unusable.

If a microwave oven, or rather its transformer, is used for the manufacture of a welding machine, then it is necessary to provide a method of cooling. For this, a fan is used, which makes it possible to control the temperature of the installed transformer, electrodes, and conductive elements. You will have to take breaks during work so that the work items can cool down on their own.

The resistance welding process itself includes 2 main stages (first, the parts are compressed to induce plastic deformation at the point that will be welded):

A pulse is turned on, after which a current is applied to the point, a liquid core is formed. The passing current creates the conditions for the expansion of the weld pool to the required parameters, plastic precipitation begins in the contact zone. Metal splashes out of the weld zone.
The current is turned off, cooling occurs, the crystallization of the metal at the junction.

A cast strong core is formed, but one of the undesirable consequences of welding is residual stresses, which can be dealt with by various methods. One of them is the delay in removing force from the lever after the current is turned off. Some experts even recommend slightly increasing the force after the current is turned off, i.e., the so-called metal forging is performed.

A transformer from an old microwave oven can be used for a variety of purposes. It can be applied to the manufacture of resistance welding machine. Such equipment is assembled from simple parts, but for this and welding itself, it is necessary to have at least a minimum work experience, to follow safety rules.

Probably every car lover or a person whose favorite hobby is repairing something dreams of an excellent welding machine. There are many different models of welding equipment on the market, but not everyone can afford it. But if there is a desire, then what to do? If there is a broken microwave at home, then you should not immediately throw it away. It only takes time and effort to create a functioning welding machine from a broken part.

Spot welding machine

This article will discuss what is a microwave transformer and its application.

Transformer

There is a transformer in the microwave oven, which is very useful for creating a device for welding. This important detail consists of two ordinary coils of copper wire, which is wound on a core. There are primary and secondary windings. Coils with windings have a different number of wire turns. This is necessary so that during the connection to the primary winding there is voltage, and a current appears inside the second due to induction, which has a lower voltage. The current must increase.

Removing the transformer

extraction

For a homemade device for welding, a transformer is used that has average power 750 W. With the use of such a device, it is possible to connect metal sheets up to one millimeter thick. This electromagnetic device belongs to step-up devices. To provide power to the magnetron, it is capable of generating a voltage that is equal to 4000 V.

A powerful electronic device (magnetron), which absolutely any microwave oven has, requires high voltage for normal operation. Therefore, the transformer, which is connected to the magnetron, has fewer turns on the first winding. There are more turns on the secondary winding, a voltage equal to 2000 V is created here. But then the voltage doubles due to the use of a specially designed doubler. Therefore, it makes no sense to measure voltage.

Remove the transformer from the microwave oven carefully and carefully. Do not use a hammer or any other heavy object. First you need to unscrew the base of this kitchen appliance, after which you need to remove all fasteners. After that, the transformer is carefully removed from the place where it is installed. From the "insides" of a microwave oven (MWF), you will need a magnetic circuit, a primary winding. The primary winding has a thick wire and fewer turns.

The secondary winding is not needed, so it is dismantled. This procedure can be carried out with a hammer or chisel. Care must be taken to avoid damage to the primary winding. If during this procedure it is found that the transformer has shunts that are a current limiter, they should be disposed of.

If the magnetic core is not a glued structure, but a welded one, then the elimination of the secondary winding must be done using a carpentry tool (chisel).

Using a chisel

An ordinary hacksaw can be a replacement for a chisel. In the event that the winding is tightly packed into the window of the magnetic wire, then the wires should be cut, and then it should be removed by drilling it. During work, care must be taken, otherwise the magnetic circuit can be deformed.

After dismantling is completed, it is necessary to wind a new secondary winding. For this process, a wire that has a diameter of one centimeter is useful. If there is no wire with this diameter, then it must be purchased. You should not bother with the fact that the wire must be stranded, you can use a bundle consisting of individual conductors. The main thing is to have the right diameter. At the end of the installation of the secondary winding, the updated transformer will be able to produce a current that will be equal to 1 kA.

If you need to do welding device with more power, then the use of one electromagnetic device is unlikely to be enough. You will have to use two devices.

Transformer upgrade features

In order to create a secondary winding, it is required to wind two or three turns on the core. This will help to get an output voltage of 2 V. And will give 0.8 kA of short-term current. These indicators are enough for the full functioning of the spot welding device.

Due to the winding of this number of turns, problems can arise if the wire has a thick insulating layer. Removing it is easy enough. It is necessary to remove the standard insulation, and then wrap the wire with electrical tape. The electrical tape must be made of cotton fabric.

Position of the new secondary winding

The wire that is used for the secondary winding should be as short as possible. This will not allow its resistance to become larger, therefore, the current strength will not become smaller.

If you need to weld metal sheets that are up to five millimeters thick, then a device with much more power is required for this purpose. To create such a unit, it is necessary to connect two whole electromagnetic devices into one circuit. To do this, you must strictly adhere to the rules. If the connection of the primary and secondary windings is incorrectly performed, a problem will arise in the form of a short circuit. In order to check whether the connection is made correctly, you need to use a voltage measuring apparatus.

After correctly connecting the windings of two electromagnetic devices, you need to find out the current strength indicator. Most often, for transformers intended for spot welding machines that are planned for use at home, current limits are made. It does not exceed 2 kA. In the event that the rate exceeds given value, there will be power outages. An ammeter should be used.

Suppose there are two identical transformers with the following parameters:

Power value - 500 W;
input voltage indicator - 220 V;
output voltage indicator - 2 V;
current strength indicator - 250 A.

If you make the correct connection, you will get twice the current strength, that is, 0.5 kA.

There will also be an increase in short-term current. But when creating a short-term current, it will be possible to see losses. This is a consequence of the huge resistance of the electrical circuit. It is necessary to connect both ends of the secondary winding with the electrodes of the unit, which is intended for spot welding.

First scheme

It happens that in the presence of two transformers with a large output voltage, the output voltage is not quite enough to create an apparatus. In this situation, it is necessary to connect their secondary windings. They must have the same number of turns.

During their connection, it is necessary to ensure that the direction of the turns is consistent. If a this condition is not fulfilled, then a protiphase will be created, and the value of the output voltage will be almost zero.

Second scheme

Definition of pins of the same name

It is possible that the terminals of the windings of electromagnetic devices to be combined are not marked. Therefore, it is necessary to determine the names of the same name. The primary and secondary windings must be connected in series. After that, voltage is applied to the input, an AC voltage measuring device must be connected to the output.

The meter can manifest itself from different sides, it depends on which direction of connection.

The measuring device can register the following:

Show voltage.
Do not register voltages in the circuit.

If the measuring device gives readings, this means that there are opposite conclusions in the circuit. This connection was not made correctly, so the following phenomena can be observed here:

The voltage value that is applied to the input of the primary windings becomes less than half.
On the secondary indicator becomes more

Therefore, the meter will show the total voltage, which is equal to twice the input value.

Transformer terminals

If the measuring device registers a zero value, this indicates that the voltages that come out of the secondary windings are equal, but have different signs. They are compensation for each other. One pair of windings is exactly connected with the same terminals.

Therefore, with the correct connection, it is necessary to focus on the voltmeter and its indicators.

electrodes

Installation of electrodes

When choosing electrodes, you need to pay attention to the diameter, which must match the diameter of the wire, because the electrodes will be connected to this wire. To do this, you can use copper bars. If a low-power apparatus is being created, then soldering iron tips can be used.

During operation, the electrodes wear out a lot. Therefore, they must be sharpened regularly. Of course, over time they will need to be replaced.

So, the wire must be connected to the electrode, this is done using a copper tip. The tip is connected by soldering.

The combination of the tip and the electrode is carried out using a bolted connection. This connection must be reliable, because with an increase in resistance in the area of \u200b\u200bunreliable contact, the device will lose its power. To avoid this problem, it is necessary to make a hole in the electrode and tip. These holes must have the same diameter.

Bolts are better to choose copper, because they have a minimum electrical resistance.

Chassis Mounting

The body can be made of wood. The back of the panel must be equipped with a switch and a power cord. For these elements, holes must be made.

This is followed by sanding, priming and painting. After that - assembly. Then you need 2 copper wires that need to be cut off. The length of the wires should be two and a half centimeters. Copper wires are electrodes. The next step is to mount the switch. Then the transformer is fixed to the tree. This fastening is made using ordinary self-tapping screws. To ensure safety and convenience, it is necessary to mount a mic. This button is attached to the upper arm. Don't forget to insulate the connections.

It is quite easy to create a spot welding unit that incorporates a transformer from an old microwave oven. The main thing is to follow certain rules and nuances, and everything will work out.