This type of welding refers to the spot method. It is convenient when you need to weld small parts to each other, or one small one. Capacitor welding is mainly used to work with non-ferrous metals.
As soon as it became possible to carry out precision welding at home, the method began to gain popularity among inexperienced welders. This situation has added relevance to the issue today. What is this process and how to do welding for home use yourself? We will try to examine this question in detail today.
The first difference that catches your eye is the welding speed and its environmental friendliness. A standard capacitor welder operates at high voltage. This allows you to save energy and get a high-quality and even seam. Its main use is in microwelding or, if necessary, welding large sections. This happens according to this principle:
As mentioned earlier, this type of welding is environmentally friendly. The devices do not require liquid for cooling due to the absence of heat emissions. This advantage allows you to add time to the life of the capacitor device.
During the spot welding process, the parts are clamped by two electrodes, which receive short-term current. Then an arc forms between the electrodes, which heats the metal, melting it. The welding pulse comes into operation within 0.1 sec., it provides a common melt core for both parts of the workpieces being welded. When the impulse is removed, the parts continue to compress under the pressure of the load. The result is a common weld.
There are secondary windings, from which the current flows to the electrodes, and the primary winding receives the pulse that was formed during the capacitor charge. In a capacitor, charge accumulation occurs in the interval between the arrival of a pulse at two electrodes. Particularly good results come when it comes to or copper. There is a limitation on the thickness of the workpieces; it should not exceed 1.5 mm. This may be a minus, but this scheme works great when welding dissimilar materials.
There are two main types of do-it-yourself capacitor welding:
Like all other types, self-condenser welding has a number of positive features:
The primary winding is passed through a diode bridge (rectifier) and then connected to a voltage source. The thyristor sends a signal to the bridge diagonal. The thyristor is controlled by a special button to start. The capacitor is connected to the thyristor, more precisely to its network, to the diode bridge, then it is connected to the winding (primary). To charge the capacitor, an auxiliary circuit with a diode bridge and a transformer is turned on.
A capacitor is used as a pulse source; its capacity should be 1000-2000 µF. To design the system, a transformer is made from a Sh40 type core, the required size is 7 cm. To make the primary winding, you need a wire with a diameter of 8 mm, which is wound 300 times. The secondary winding involves the use of a copper bus with 10 windings. Almost any capacitors are used for the input, the only requirement is a power of 10 V, a voltage of 15.
When the work requires connecting workpieces up to 0.5 cm, it is worth applying some adjustments to the design diagram. For more convenient signal control, use the MTT4K series trigger; it includes parallel thyristors, diodes and a resistor. An additional relay will allow you to adjust the working time.
This homemade capacitor welding works using the following sequence of actions:
After the capacitor welding has been assembled with our own hands, we are ready to begin work. First, you should prepare the parts by cleaning them from rust and other dirt. Before placing the workpieces between the electrodes, they are connected in the position in which they need to be welded. Then the device starts. Now you can squeeze the electrodes and wait 1-2 minutes. The charge that accumulates in the high-capacity capacitor will pass through the welded fasteners and the surface of the material. As a result, it melts. Once these steps have been completed, you can proceed to the next steps and weld the remaining parts of the metal.
Before welding work at home, it is worth preparing materials such as sandpaper, grinder, knife, screwdriver, any clamp or pliers.
Capacitor welding is very widely used both at home and in industrial areas; as we see, it is very convenient and easy to use, plus it has a large number of advantages. With the help of the information provided, you will be able to take your knowledge to a new level and successfully apply spot welding in practice.
The device that we will present in this article is called “capacitor welding”. This welding can be used to connect very small or thin objects and parts. Its difference from standard spot welding is that the heating of the joint of parts is carried out due to the energy of the discharge of capacitors.
Lots of electronic fun stuff in this Chinese store.
The convenience of this type of design lies in the relative simplicity of the electrical circuit, which you can assemble with your own hands. The model presented in the video is powered by a welding transformer; alternating current is converted by a rectifier. The voltage is 70 volts. The current flows through the capacitance, which, if necessary, can be replaced with a conventional resistance of 10 kOhm. After resistance, the current flows to a capacitor bank with a total capacity of 30,000 microfarads. The accumulated charge on the capacitors is released through the thyristor.
After turning on the power, the light comes on, which in this case plays the role of a voltage indicator. When the light stops lighting, it means the capacitor bank is fully charged. After this you are ready to go. The discharge is activated by pressing a button built into the holder. This welding allows you to weld not only thin plates, but also studs of different diameters to metal surfaces. For this purpose, it is possible to hold the pin in the holder.
Discussion
Urnfry yvovlya
+azim meex have you ever touched the terminals of a charged 3.8 uF 250 V capacitor? At the beginning of the video it was said: 30,000 microfarads of voltage is supplied at 70 volts, as a result we get 73.5 joules, this is at least. The range of 10-50 J per impulse already loses its non-lethality and can cause electrical injuries incompatible with life (cardiac fibrillation, death).
Urnfry yvovlya
+azim meex
70 volts is the minimum voltage for the capacitor, since it supplies power from 70. What does the drop have to do with it? Check it out, and then tell me about the path it takes.
Alexey Grachev
+toyama tokanava in a humid room with a bunch of metal utensils all around? Moreover, the voltage is probably indicated not as constant, but as variable, right? No, you can kill yourself with 12 volts if you want, but I haven’t met such people. And then, almost all transformer welding works at a voltage of about 70 volts and no special problems arise.
toyama tokanava
I'm not even against it, but there are certain rules for use, I speak as a former welder and a former electrician. Safety rules to help you.
Vladimir lokot
+aleksey grachev a fully charged capacitor with a hundred times smaller capacity when discharged through a finger makes 2 burnt holes in it, quite deep by the way, this is basically not fatal, but it’s damn painful. I don’t even know what to compare it with - it’s much more painful than a wasp sting, for example. But to be honest, I’m afraid to imagine what kind of “holes” this fool will burn.
Alexey Grachev
+vladimir lokot it all depends on the voltage. You can charge a hundred farads at 30 volts and upon contact with your finger it will only pinch, or you can charge one microfarad at a thousand volts and then it won’t seem enough, there will be holes and whatever you want. Ohm's law, damn it.
Vladimir lokot
+ Alexey Grachev there is more than 30 volts, but even 30 volts is enough for a normal breakdown of the skin. And in this case, the charge is essentially important, and it directly depends on the capacity of the capacitor bank.
Alexey Grachev
+vladimir lokot yes, there are 70 volts. I have felt this voltage on myself more than once, since I regularly cook with both alternating and direct current, in the latter case through a diode bridge and capacitors. It’s noticeable, of course, but obviously not to the full power of the welder; I’m not an iron man. So Ohm’s law rules and it doesn’t matter to him what the circuit is powered by - a power plant, batteries or capacitors.
Vladimir lokot
+ Alexey Grachev doesn’t want to argue with you, but 70 volts from a welder is garbage compared to the instantaneous discharge of a capacitor battery of good capacity; Even 220V from a power socket is garbage. And Ohm’s law, which you mentioned in vain twice here, perfectly describes why, if you think about it a little. When such a capacitor is instantly discharged, a short-term but very large current is obtained, and this is very, very serious.
Alexey Grachev
+vladimir lokot yes, they discharge quickly, remember the same lightning, but if you close them through a resistance or a voltmeter (which itself is essentially a resistance), the process will slow down depending on the number of ohms indicated on the resistor.
Vladimir lokot
+ Alexey Grachev I don’t want to convince you, but do a simple experiment: charge a capacitor of at least 50-100 uF to 50-100V and touch its legs with your finger. Then tell us how the resistance of the skin affects the discharge rate of the capacitor; no, it will have an effect, of course it will, of course. There are people who twist 220 wires while holding 2 wires and it only tingles. Or which the police stun gun is completely ignored. But these are rather exceptions.
Alexey Grachev
+vladimir lokot several messages above I already wrote about the presence of welding with capacitors. The fact that 70 volts hit you noticeably does not prove anything. Farewell.
Sergey pn
Dangerous. You can hit someone on the head with this crap and it will be bad. Otherwise, there’s nothing dangerous, why talk about something we don’t understand.
Sapar malikov
I constantly repair amplifiers there +/-100 volts DC and capacitors in modern amplifiers are at least 4 pieces of 10,000 uF at 100 volts, sometimes we forget to discharge the capacitors with a strong current, of course, but there won’t be any holes, especially since the constant is not very harmful to life
alexandr developer
50 or 100? The difference seems to be twofold. Of course, it’s different for everyone, but I calmly held on to the terminals of the laboratory power supply when it read 90. I was about 13 then and nothing. (Of course, I don’t recommend repeating this, especially if the power supply is without current protection, or even more so if the power supply is a pulse generator. Or you are standing on a metal floor barefoot). On the topic - I absolutely don’t understand why there is 70c. I think that when discharging, the capacitors switch into a parallel connection - the capacitance and discharge current increase and the voltage drops. In addition, the charge there is limited and, in theory, these 70 volts that come in should go through a galvanic isolation (transformer) - if you stand with your bare feet on metal and do not apply or apply the second electrode poorly, it may shock you, but certainly not kill you.
Sergey psg
scheme.
https://fotki.Yandex.Ru/next/users/ink740/album/41349/view/852249
https://fotki.Yandex.Ru/next/users/ink740/album/41349/view/852248
scheme. Personally, I would collect it this way.
If you exclude the diode between 1 and 2 and the jumper between 3 and 4, then you can insert a diode bridge. Hint as below picture. Too lazy to draw 2 identical ones.
The nominal values of the parts must be counted. Under specific conditions.
A competent person will figure it out, but a competent person in another area of skills will pay a competent person in electronics and electrical engineering.)
Logic of work.
1. Turned on 220, all switches are open.
2. Closed button 1 and wait for the charging current to stop (the lamp has gone out).
3. Open button 1, briefly close (or hold) button 2. We weld the part.
4. Opened switch 2.
If I made an inaccuracy somewhere, I think Alexander will correct me.
Sergey psg
+dim russ I haven’t made yet.
The author in the video says the capacitor capacity is 30 thousand microfarads. The voltage on the bridge is 70 volts = on the capacitors 100-110 volts. The capacitors themselves must be taken at a higher voltage of 125-160 volts. 160 is even better. I don't remember the range of voltages for capacitors. Whether it is possible to answer more or less can only be answered by practice. Place the container in a larger position, so it is possible that the surface being welded will burn out (burning), may the welders forgive me. Put less, there won’t be enough energy for the process. Is it possible to reduce the voltage? Yes you can, but! If my memory serves me correctly, the dependence of the amount of stored energy on the voltage in the capacitors is quadratic. That is, the voltage is 2 times lower = the energy is 4 times lower.
Therefore, first do as the author says: 70 volts on the secondary = 100 volts on the condensers * 30 thousand microfarads. And then if something doesn’t suit you, select the parameters for yourself. Because welding the lead to the battery is one thing, but using it in auto straightening is more powerful.
Evgeniy Fedorov
Helpful information! I do contact welding without any electronics, although the button is via a thyristor on the primary. For small thicknesses there is a timer. I weld plates with a thickness of 01 to 1.5 mm.
azim meex
+vahe vardanyan, firstly, the powder will blow over the welder’s hands and face, secondly, the graphite will carbonize the welding point (not the seam), which will make it more fragile and thirdly, it will reduce the resistance of the welding site and, at the same time, the thermal effect of the current.
Alexey Polushkin
the energy of a charged capacitor is converted into heat, under the influence of which the metal melts at points with minimal resistance, that is, in places where it is pressed by electrodes. The energy of the capacitor is e=c*u*u/2, which means that by raising the voltage by 2 times, we increase the energy by 4 times. Many capacitors are better than one, because due to the design features, a single capacitor is not capable of delivering a large current during a short circuit, and can quickly become unusable. Therefore, from a bank of parallel capacitors we will get a noticeably higher current than from one if it had the same capacity as the entire battery.
Valery Lysenko
+ Sergey psg if this is easy for you, then draw a diagram. Take a screenshot or post a photo of this leaflet on a social network. And send us the link. Don't let your tongue run wild that it's simple. I'll figure out the diagram.
Petrow60
good health. A very interesting topic, if it would be possible to publish a diagram with parameters. This video deserves like and respect. Thank you. I look forward to the continuation as a subscriber.
Toyama tokanawa
If you add a pulse current transformer at the output with a turns ratio of one to ten, you can get ten times more current at the electrodes. Take the cross-section of the wires of the windings according to the current in them, the number of turns does not even need to be large, so take it, ten turns and the secondary one turn. I even think it’s possible to weld the reinforcement. I had to repair a welding installation in the fitting shop; they used a mercury rectifier of about 1000 volts and oil capacitors of 100 microfarads, and thyristor control almost similar to yours.
Denis
Dear video author! I do welding similar to yours. I use a capacitor ea-ii-10 with a nominal value of 33000 uF, a voltage of 63 V and a thyristor T-160. I charge the capacitor with a power supply.
From the “+” of the capacitor a wire goes to the anode of the thyristor, and from the cathode of the thyristor it goes to the welding electrode, “-” from the capacitor also goes to the welding electrode. The voltage to the control electrode of the thyristor comes from the “+” capacitor through a micro switch. The thyristor is working, I checked it, and so is the capacitor. For some reason, the thyristor does not open instantly (when the thyristor opens, the voltmeter needle smoothly begins to go to zero) and welding does not occur. Please tell me what could be the problem? Thanks in advance.
Sungazer
+ Denis put on Well, first of all, a thyristor is a powerful, but slow thing.
And secondly, Conder electrolyte is not designed for high currents.
Therefore, during prolonged operation the condenser will overheat. Therefore, it is better to dial the condensers in small denominations and parallel them.
Yury galinsh
+sungazer how to understand “slow thing”? In network power regulators, at a frequency of 50 Hz, the thyristor (semistor) fires 50 (or 100) times per second. Moreover, it “cuts” the sinusoid almost vertically. In this particular case, this is an ordinary switch.
An electrolytic capacitor drops, if I’m not mistaken, 80% of its capacity in milliseconds.
I can assume that the thyristor itself is faulty. And as far as I remember, a current limiter (resistor) was installed at the control electrode. Well, the capacitor can smoothly discharge through the control electrode.
Alexander polyulyakh
You need to look for components on radio markets or order them on the Internet. Everything is. The greater the capacitance of the capacitors, the greater the charge. The microswitch sends micro currents to the thyristor and it instantly releases the entire impulse of the accumulated energy of the capacitors.
User0011
+ look for Anton Tumanov at scrap metal collection points! They don’t use aluminum for scrap; they don’t take thin scrap metal or aluminum foil! Therefore, you can buy at the price of ferrous metal. No need to overpay somewhere in the markets! And if you get the receivers interested (etc.). There is so much of this “barrel”, and so much of this one. You can collect it quickly.
slonik wrote:
after the rectifier bridge there is a set of condensers (7 pieces in parallel) and then a choke. So these condensers are designed so that you can connect them with jumpers or the rectifier field, or after the choke, or even turn them off. So why is this necessary? And where is the best place to install these condensers? And what are they worth?
Tribune wrote:
To ensure the conditions for stabilizing the arc gap, the source for semi-automatic welding must have a rigid load characteristic and a high rate of current rise during a short circuit. These requirements are especially relevant when welding with thin wire D0.6...0.8mm. As the wire diameter increases, the load characteristic becomes more decreasing and the required rate of current rise decreases. To correct the rate of current rise, on classical sources, the choke is even made with taps (BC300).
Judging by the stated current of 140A, the source is designed for welding with thin wire and most likely the capacitor should be turned on before the choke. In this case, the inductance of the inductor should be about 0.2 mH. Turning on a capacitor after the inductor almost always leads to an excessively high rate of current rise, which is not good (spattering increases sharply).
valvol.ru
Bugaev Victor, Vitaly Diduk, Maxim Musienko
Aluminum electrolytic capacitors are one of the main elements that ensure stable operation of high-frequency inverters of welding machines. Reliable high-quality capacitors for this type of application are produced by Hitachi, Samwha, Yageo.
The first devices using the electric arc welding method used adjustable alternating current transformers. Transformer welding machines are the most popular and are still used today. They are reliable, easy to maintain, but have a number of disadvantages: heavy weight, high content of non-ferrous metals in the transformer windings, low degree of automation of the welding process. It is possible to overcome these disadvantages by moving to higher current frequencies and reducing the size of the output transformer. The idea of reducing the size of the transformer by moving from a power supply frequency of 50 Hz to a higher one was born back in the 40s of the 20th century. Then this was done using electromagnetic transducers-vibrators. In 1950, electron tubes - thyratrons - began to be used for these purposes. However, it was undesirable to use them in welding technology due to low efficiency and low reliability. The widespread introduction of semiconductor devices in the early 60s led to the active development of welding inverters, first on a thyristor basis, and then on a transistor one. Insulated gate bipolar transistors (IGBTs) developed at the beginning of the 21st century gave new impetus to the development of inverter devices. They can operate at ultrasonic frequencies, which can significantly reduce the size of the transformer and the weight of the device as a whole.
A simplified block diagram of the inverter can be represented as three blocks (Figure 1). At the input there is a transformerless rectifier with a parallel-connected capacitance, which allows you to increase the DC voltage to 300 V. The inverter unit converts DC into high-frequency alternating current. The conversion frequency reaches tens of kilohertz. The unit includes a high-frequency pulse transformer in which the voltage is reduced. This block can be manufactured in two versions - using single-cycle or push-pull pulses. In both cases, the transistor unit operates in switching mode with the ability to adjust the on-time, which allows you to regulate the load current. The output rectifier unit converts the alternating current after the inverter into direct welding current.
Rice. 1. Simplified block diagram of a welding inverter
The principle of operation of the welding inverter is the gradual conversion of the mains voltage. First, the AC mains voltage is increased and rectified in the preliminary rectification unit. A constant voltage powers a high-frequency generator using IGBT transistors in the inverter unit. The high-frequency alternating voltage is converted to a lower one using a transformer and supplied to the output rectifier unit. From the output of the rectifier, current can already be supplied to the welding electrode. The electrode current is regulated by circuitry by controlling the depth of negative feedback. With the development of microprocessor technology, the production of inverter semi-automatic machines began, capable of independently selecting the operating mode and performing such functions as “anti-sticking”, high-frequency arc excitation, arc retention and others.
The main components of welding inverters are semiconductor components, a step-down transformer and capacitors. Today, the quality of semiconductor components is so high that if they are used correctly, no problems arise. Due to the fact that the device operates at high frequencies and fairly high currents, special attention should be paid to the stability of the device - the quality of the welding work directly depends on it. The most critical components in this context are electrolytic capacitors, the quality of which greatly affects the reliability of the device and the level of interference introduced into the electrical network.
The most common are aluminum electrolytic capacitors. They are best suited for use in the primary network IP source. Electrolytic capacitors have high capacitance, high rated voltage, small dimensions, and are capable of operating at audio frequencies. Such characteristics are among the undoubted advantages of aluminum electrolytes.
All aluminum electrolytic capacitors are composed of sequential layers of aluminum foil (the anode of the capacitor), a paper spacer, another layer of aluminum foil (the cathode of the capacitor) and another layer of paper. All this is rolled up and placed in an airtight container. Conductors are brought out from the anode and cathode layers for inclusion in the circuit. Also, the aluminum layers are additionally etched in order to increase their surface area and, accordingly, the capacitance of the capacitor. At the same time, the capacity of high-voltage capacitors increases by about 20 times, and low-voltage ones by 100. In addition, this entire structure is treated with chemicals to achieve the required parameters.
Electrolytic capacitors have a rather complex structure, which makes them difficult to manufacture and operate. The characteristics of capacitors can vary greatly under different operating modes and operating climatic conditions. With increasing frequency and temperature, the capacitance of the capacitor and ESR decreases. As the temperature decreases, the capacitance also drops, and the ESR can increase up to 100 times, which, in turn, reduces the maximum permissible ripple current of the capacitor. The reliability of pulse and input network filter capacitors, first of all, depends on their maximum permissible ripple current. Flowing ripple currents can heat up the capacitor, which causes its early failure.
In inverters, the main purposes of electrolytic capacitors are to increase the voltage in the input rectifier and smooth out possible ripples.
Significant problems in the operation of inverters are created by large currents through transistors, high requirements for the shape of control pulses, which implies the use of powerful drivers to control power switches, high requirements for the installation of power circuits, and large pulse currents. All this largely depends on the quality factor of the input filter capacitors, so for inverter welding machines you need to carefully select the parameters of electrolytic capacitors. Thus, in the preliminary rectification unit of a welding inverter, the most critical element is the filtering electrolytic capacitor installed after the diode bridge. It is recommended to install the capacitor in close proximity to the IGBT and diodes, which eliminates the influence of the inductance of the wires connecting the device to the power source on the operation of the inverter. Also, installing capacitors near consumers reduces the internal resistance to alternating current of the power supply, which prevents excitation of the amplifier stages.
Typically, the filter capacitor in full-wave converters is chosen so that the ripple of the rectified voltage does not exceed 5...10 V. It should also be taken into account that the voltage on the filter capacitors will be 1.41 times greater than at the output of the diode bridge. Thus, if after the diode bridge we get 220 V pulsating voltage, then the capacitors will already have 310 V DC voltage. Typically, the operating voltage in the network is limited to 250 V, therefore, the voltage at the filter output will be 350 V. In rare cases, the mains voltage can rise even higher, so capacitors should be selected for an operating voltage of at least 400 V. Capacitors can have additional heating due to high operating currents. The recommended upper temperature range is at least 85...105°C. Input capacitors for smoothing out rectified voltage ripples are selected with a capacity of 470...2500 µF, depending on the power of the device. With a constant gap in the resonant choke, increasing the capacitance of the input capacitor proportionally increases the power supplied to the arc.
There are capacitors on sale, for example, of 1500 and 2200 µF, but, as a rule, instead of one, a bank of capacitors is used - several components of the same capacity connected in parallel. Thanks to parallel connection, internal resistance and inductance are reduced, which improves voltage filtering. Also, at the beginning of the charge, a very large charging current flows through the capacitors, close to the short circuit current. Parallel connection allows you to reduce the current flowing through each capacitor individually, which increases the service life.
On the electronics market today you can find a large number of suitable capacitors from well-known and little-known manufacturers. When choosing equipment, one should not forget that with similar parameters, capacitors differ greatly in quality and reliability. The most well-proven products are from such world-famous manufacturers of high-quality aluminum capacitors as Hitachi, Samwha and Yageo. Companies are actively developing new technologies for the production of capacitors, so their products have better characteristics compared to competitors' products.
Aluminum electrolytic capacitors are available in several form factors:
Tables 1, 2 and 3 present the series of the above manufacturers that are most optimal for use in the pre-rectification unit, and their appearance is shown in Figures 2, 3 and 4, respectively. The given series have a maximum service life (within the family of a particular manufacturer) and an extended temperature range.
Table 1. Electrolytic capacitors manufactured by Yageo
Table 2. Electrolytic capacitors manufactured by Samwha
Table 3. Electrolytic capacitors manufactured by Hitachi
| Name | Capacity, µF | Voltage, V | Ripple current, A | Dimensions, mm | Form factor | Service life, h/°C |
| HP3 | 470…2100 | 400, 420, 450, 500 | 2,75…9,58 | 30×40, 35×35…40×110 | Snap-In | 6000/85 |
| HU3 | 470…1500 | 400, 420, 450, 500 | 2,17…4,32 | 35×45, 40×41…40×101 | Snap-In | 6000/105 |
| HL2 | 470…1000 | 400, 420, 450, 500 | 1,92…3,48 | 35×40, 30×50…35×80 | Snap-In | 12000/105 |
| GXA | 1000…12000 | 400, 450 | 4,5…29,7 | 51×75…90×236 | Screw Terminal | 12000/105 |
| GXR | 2700…11000 | 400, 450 | 8,3…34,2 | 64×100…90×178 | Screw Terminal | 12000/105 |
As can be seen from Tables 1, 2 and 3, the product range is quite wide, and the user has the opportunity to assemble a capacitor bank, the parameters of which will fully meet the requirements of the future welding inverter. The most reliable are Hitachi capacitors with a guaranteed service life of up to 12,000 hours, while competitors have this parameter up to 10,000 hours in Samwha JY series capacitors and up to 5,000 hours in Yageo LC, NF, NH series capacitors. True, this parameter does not indicate a guaranteed failure of the capacitor after the specified line. Here we mean only the time of use at maximum load and temperature. When used in a smaller temperature range, the service life will increase accordingly. After the specified period, it is also possible to reduce the capacity by 10% and increase losses by 10...13% when operating at maximum temperature.
Rice. 2. Yageo electrolytic capacitors
Rice. 3. Samwha electrolytic capacitors
Rice. 4. Hitachi electrolytic capacitors
It is noteworthy that in each series you can find a different configuration of capacitor leads - with reinforced snap-in terminals or bolted terminals. Bolted terminals provide guaranteed reliability of the assembly, and capacitors with latched terminals add to the reliability and ease of installation on a printed circuit board.
The considered high-quality aluminum electrolytic capacitors manufactured by Hitachi, Samwha and Yageo can solve almost any problem in the development of a high-frequency inverter welding machine. A distinctive feature of the presented capacitors is that they are developed in accordance with the requirements of RoHS (Directive on the Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment) and other environmental standards. For advice on application, as well as on the purchase of capacitors produced by all three companies, you can contact their distributor - the COMPEL company.
Obtaining technical information, ordering samples, ordering and delivery.
www.compel.ru
How to make your own semi-automatic welding machine. This question worries many, since the cost of a semi-automatic welding machine for domestic purposes ranges from $300 to $800. Industrial semi-automatic welding machines are even more expensive. There is only one option left - to assemble the semi-automatic machine yourself, with your own hands. Let's consider what main components and parts a semi-automatic welding machine consists of. The basis of the semi-automatic welding machine is a welding power transformer. It is advisable to have a ready-made transformer, but you can make it yourself. The main requirements for the transformer are that with an output voltage of 10 - 20V, ensuring a rated output current of up to 60A. To adjust the output voltage, when winding the primary winding, it is necessary to make taps and provide a switching option.
Of course, the most difficult component to make at home is the wire feed mechanism. The quality of the weld and the uniformity of the wire feed will directly depend on its operation. The most suitable option for manufacturing a feed mechanism is a gearbox from a car windshield wiper complete with an electric motor.
Because Semi-automatic welding is performed with direct current, it is necessary to use a rectifier. The type of rectifier depends on the method of winding the welding transformer. For our version, with two windings, two DL161-200 rectifier diodes are used. For a bridge rectifier circuit, four rectifier diodes are used. The 30000x63V capacitor is designed to smooth out voltage ripples after the rectifier.
In the DC circuit, after the rectifier diodes, to improve the stability of the arc, a choke is installed, wound on a transformer core with a cross-section of at least 35 mm x 35 mm, about 20 turns of wire, the diameter of which is not less than the diameter of the wire on the secondary winding of the welding transformer.
The electric motor of the wire feed drive mechanism is powered from a power supply with an output voltage of 12 - 15V and a current of about 5A.
The semi-automatic welding machine also has:
gas solenoid valve;
electromagnetic starter for switching on a semi-automatic welding machine;
wire feeding sleeve
and other little things.
The diagram of the semi-automatic welding machine is shown below:
A variable resistor is used to adjust the wire feed speed during operation of the semiautomatic machine. When you press the start button, the gas supply valve is synchronously turned on and the welding transformer is turned on using relay K1.
This semi-automatic welding circuit is just an example. When making it yourself, the semi-automatic circuit can be changed based on the available components.
There are several ways to seamlessly join metal elements, but among all of them, capacitor welding occupies a special place. The technology has become popular since about the 30s of the last century. Docking is carried out by supplying electric current to the desired location. A short circuit is created, which allows the metal to melt.
The most interesting thing is that capacitor welding can be used not only in industrial conditions, but also in everyday life. It involves the use of a small-sized device that has a constant voltage charge. Such a device can easily move around the work area.
Among the advantages of the technology, it should be noted:
However, there are situations when it is impossible to use capacitor welding to connect parts. This is primarily due to the short duration of the power of the process itself and the limitation on the cross-section of combined elements. In addition, pulsed load can create various interferences in the network.
The process of joining workpieces itself involves contact welding, for which a certain amount of energy is consumed in special capacitors. Its release occurs almost instantly (within 1 - 3 ms), due to which the thermal impact zone is reduced.
It is quite convenient to carry out capacitor welding with your own hands, since the process is economical. The device used can be connected to a regular electrical network. There are special high-power devices for industrial use.
The technology has gained particular popularity in workshops designed to repair vehicle bodies. During the work they are not burned or subjected to deformation. There is no need for additional straightening.
In order for capacitor welding to be performed at a high quality level, certain conditions must be adhered to.
There are three options for influencing workpieces:
As for the classification according to the equipment used, the technology can be divided according to the presence of a transformer. In its absence, the design of the main device is simplified, and the bulk of the heat is released in the direct contact zone. The main advantage of transformer welding is the ability to provide a large amount of energy.
To connect thin sheets up to 0.5 mm or small parts, you can use a simple design made at home. In it, the impulse is supplied through a transformer. One of the ends of the secondary winding is connected to the array of the main part, and the other to the electrode.
In the manufacture of such a device, a circuit can be used in which the primary winding is connected to the electrical network. One of its ends is output through the diagonal of the converter in the form of a diode bridge. On the other hand, a signal is supplied directly from the thyristor, which is controlled by the start button.
The pulse in this case is generated using a capacitor having a capacity of 1000 - 2000 μF. To manufacture a transformer, a Sh-40 core with a thickness of 70 mm can be used. The primary winding of three hundred turns can be easily made from wire with a cross-section of 0.8 mm marked PEV. A thyristor with the designation KU200 or PTL-50 is suitable for control. The secondary winding with ten turns can be made of a copper busbar.
To increase power indicators, the design of the manufactured device will have to be changed. With the right approach, it will be possible to connect wires with a cross-section of up to 5 mm, as well as thin sheets no more than 1 mm thick. To control the signal, a contactless starter marked MTT4K, designed for an electric current of 80 A, is used.
Typically, the control unit includes thyristors connected in parallel, diodes and a resistor. The response interval is adjusted using a relay located in the main circuit of the input transformer.
The energy is heated in electrolytic capacitors, combined into a single battery using the table. You can see the necessary parameters and the number of elements.
The main transformer winding is made of wire with a cross-section of 1.5 mm, and the secondary winding is made of a copper busbar.
The homemade device operates according to the following scheme. When you press the start button, the installed relay is activated, which, using thyristor contacts, turns on the transformer of the welding unit. The shutdown occurs immediately after the capacitors are discharged. The pulse effect is adjusted using a variable resistor.
The manufactured device for capacitor welding must have a convenient welding module that provides the ability to fix and freely move the electrodes. The simplest design involves manually holding the contact elements. In a more complex version, the lower electrode is fixed in a stationary position.
To do this, it is fixed on a suitable base with a length of 10 to 20 mm and a cross-section of more than 8 mm. The upper part of the contact is rounded. The second electrode is attached to a platform that can move. In any case, adjustment screws must be installed, with the help of which additional pressure will be applied to create additional pressure.
It is imperative to isolate the base from the moving platform before the contact of the electrodes.
Before doing capacitor spot welding with your own hands, you need to familiarize yourself with the main steps.
Work can be carried out using special equipment. This kit usually includes:
The described technology for connecting metal elements allows not only to weld steel products. With its help, you can easily join parts made of non-ferrous metals. However, when performing welding work, it is necessary to take into account all the features of the materials used.
Technical data of our semi-automatic welding machine:
Supply voltage: 220 V
Power consumption: no more than 3 kVA
Operating mode: intermittent
Operating voltage regulation: stepwise from 19 V to 26 V
Welding wire feed speed: 0-7 m/min
Wire diameter: 0.8mm
Welding current value: PV 40% - 160 A, PV 100% - 80 A
Welding current control limit: 30 A - 160 A
A total of six such devices have been made since 2003. The device shown below in the photo has been in service since 2003 in a car service center and has never been repaired.
At all
Front view
Back view
Left view
The welding wire used is standard
5kg coil of wire with a diameter of 0.8mm
Welding torch 180 A with Euro connector
was purchased at a welding equipment store.
Installation view
Control board
A single-phase 16A type AE circuit breaker is used as a power and protection switch. SA1 - welding mode switch type PKU-3-12-2037 for 5 positions.
Resistors R3, R4 are PEV-25, but they don’t have to be installed (I don’t have them). They are designed to quickly discharge choke capacitors.
Now for capacitor C7. Paired with a choke, it ensures combustion stabilization and arc maintenance. Its minimum capacity should be at least 20,000 microfarads, optimal 30,000 microfarads. Several types of capacitors with smaller dimensions and higher capacity were tried, for example CapXon, Misuda, but they did not prove to be reliable and burned out.
As a result, Soviet capacitors were used, which still work to this day, K50-18 at 10,000 uF x 50V, three in parallel. 
Power thyristors for 200A are taken with a good margin. You can install it at 160 A, but they will work at the limit, and you will need to use good radiators and fans. The used B200s stand on a small aluminum plate.
Relay K1 type RP21 for 24V, variable resistor R10 wirewound type PPB.
When you press the SB1 button on the burner, voltage is supplied to the control circuit. Relay K1 is activated, thereby, through contacts K1-1, voltage is supplied to the electromagnetic valve EM1 for acid supply, and K1-2 - to the power supply circuit of the wire drawing motor, and K1-3 - to open the power thyristors.
Switch SA1 sets the operating voltage in the range from 19 to 26 Volts (taking into account the addition of 3 turns per arm up to 30 Volts). Resistor R10 regulates the supply of welding wire and changes the welding current from 30A to 160A.
When setting up, resistor R12 is selected in such a way that when R10 is turned to minimum speed, the engine still continues to rotate and does not stand still.
When you release the SB1 button on the torch, the relay releases, the motor stops and the thyristors close, the solenoid valve, due to the charge of capacitor C2, still remains open, supplying acid to the welding zone.
When the thyristors are closed, the arc voltage disappears, but due to the inductor and capacitors C7, the voltage is removed smoothly, preventing the welding wire from sticking in the welding zone.
Fiberglass - in my opinion, the best insulation is obtained
We continue to wind - the secondary. We take an aluminum busbar in glass insulation measuring 2.8x4.75 mm (can be purchased from wrappers). You need about 8 m, but it is better to have a small margin. We begin to wind, laying it as tightly as possible, we wind 19 turns, then we make a loop for the M6 bolt, and again 19 turns. We make the beginnings and ends 30 cm each, for further installation.
Here is a small digression, personally, for me to weld large parts at such a voltage, the current was not enough; during operation, I rewound the secondary winding, adding 3 turns per arm, in total I got 22+22.
The winding fits snugly, so if you wind it carefully, everything should work out.
If you use an enamel wire as a primary material, then you must impregnate it with varnish; I kept the coil in the varnish for 6 hours.
We assemble the transformer, plug it into an outlet and measure the no-load current of about 0.5 A, the voltage on the secondary is from 19 to 26 Volts. If everything is so, then the transformer can be put aside; we no longer need it for now.
Instead of OSM-1 for a power transformer, you can take 4 pieces of TS-270, although the dimensions are slightly different, and I only made 1 welding machine on it, so I don’t remember the data for winding, but it can be calculated.
We still have one more transformer to power the control circuit (I took a ready-made one). It should produce 24 volts at a current of about 6A.
Motor M is used from a VAZ-2101 windshield wiper.
The limit switch for returning to the extreme position has been removed.
In the bobbin holder, a spring is used to create braking force, the first one that comes to hand. The braking effect is increased by compressing the spring (i.e. tightening the nut).
