How many microphone capacitors for a homemade semi-automatic. Electrolytic capacitors in welding inverters. Choice of electrolytes from Hitachi, Samwha, Yageo

12.03.2020

There are many welding technologies various materials and among them - capacitor welding. The technology has been known since the 30s of the last century and is a variety. The connection of metals occurs during melting in places of a short circuit of the electric current due to the applied energy of the discharge of charged high-capacity capacitors. The process takes 1-3 milliseconds.

The basis of the apparatus is a capacitor or a block of capacitors, which are charged by a DC power supply. Capacitor electrodes, after reaching the required energy level during the charging process, are connected to the welding points. The current flowing during the discharge between the parts to be welded causes the surfaces to heat up to such an extent that the metal melts and quality is formed.

Despite a number of advantages, capacitor welding has a number of limitations that do not allow it to be used everywhere. Among them:

Accounts

free trial

Equipment advantages

high process speed in automated production, up to 600 points per minute

accuracy of connection of parts and repeatability of processes on the line

does not transmit infrared and ultraviolet radiation

equipment durability

welding of different metals

low heat generation, no need for coolant

lack of such Supplies like electrodes or welding wire

Despite some shortcomings, the method of joining metals has been widely used in industry and in everyday life.

Types of welding capacitor machines

There are two types of capacitor welding machines - with the discharge of energy storage devices directly on the surfaces to be welded and with a discharge from the secondary winding of the transformer. The first, transformerless method, is more often used in shock-capacitor welding. The second method, transformer, is used to create a high-quality seam.

Shock-capacitor equipment welds the parts during the impact of one of the electrodes on the part. During impact, the surface parts are tightly pressed against each other. A capacitor discharge occurs, forming a microarc that heats the surfaces to the melting point of metals. The parts are firmly connected.

In the transformer welding method, the capacitor after charging is connected to the primary winding of the step-down transformer. A potential appears on the secondary winding, several times smaller than the amplitude of the incoming pulse. During the discharge, parts are welded, the capacitor is charged again and again gives energy to the primary winding of the transformer. This allows for long bursts of up to 5 discharges per second, which create strong and precise welds.

Application Specifics

Capacitor welding is an economical process, so it is convenient to use it at home with a single-phase low power network. The industry produces household welders with a power of 100-400 watts, which are designed for home use or in small private workshops.

Capacitor welding has gained particular popularity in car body repair shops. Unlike arc welding, capacitor welding does not burn through and does not deform the thin walls of sheets of body parts. There is no need for additional straightening.

Also, capacitor welding is used in radio electronics for welding products that are not soldered using conventional fluxes or fail from overheating.

Capacitor welders are used by jewelers to make or repair jewelry.

In industry, the point connection is used for:

welding of bolts, hooks, nuts, studs and other hardware to surfaces;
interconnection of different metals, including non-ferrous;
welding of watch parts, photo and film equipment;
manufacture of optical and lighting devices;
assembly of electronic equipment
and etc.

Capacitor welding is used to connect microscopic parts that cannot be welded with an arc method.

Do-it-yourself capacitor apparatus

A capacitor-type welding machine can be made independently and used for domestic purposes. For this you will need

transformer for 220 volts with a power of 5-20 W with an output voltage of 5V;
four rectifier diodes with a direct current of at least 300mA (for example, D226b);
thyristor PTL-50, modern replacement for T142-80-16, KU 202 or similar;
electrolytic capacitor 1000.0 x25 V;
variable resistor 100 ohm;
transformer with a power of at least 1000 W (suitable for microwave ovens);
electrodes or a welding gun (different designs are described many times on the Internet pages);
copper wire with a cross section of at least 35 mm2 - 1 meter.
switches, fuses, housing at the discretion.

If the installation is carried out according to the scheme without errors and the parts are in good order, then there will be no problems with the performance of the device.

There is only one problem - the output transformer. If you really decide to use a microwave transformer, and you can buy it cheaply in the markets for used parts, then get ready that it needs to be redone.

It is necessary to remove the magnetic shunts and the secondary winding and wind 2-5 turns of the secondary winding with a thick copper wire on the vacated place. During the tuning process, the number of turns may need to be changed. It is considered optimal that the output voltage should fluctuate within 2-7 volts, but this value also depends on the duration of the welding pulse, the thickness of the materials being welded. No need to be afraid to experiment by choosing different modes with a variable resistor and changing the number of turns. But do not try to get out of the apparatus what a conventional arc process can do. It will not work to cook water pipes and fittings, this device is for other purposes.

Apparatus for the transformerless type is not much more complicated, but they are more cumbersome. You will need a set of capacitors with a total capacity of about 100,000 microfarads. This is a decent size and weight battery. It can be replaced with a compact ionistor, but the device is not cheap. In addition, electrolytic capacitors are not durable. Therefore, portable and household capacitor spot welding machines are usually manufactured according to a transformer circuit.

Modern devices are manufactured using slightly different technologies. The frequency and power of the discharge is regulated by PIC controllers, it is possible to automate processes, control via a computer or monitor interface. But the physical processes of welding have not changed. Having assembled the simplest unit once, you can later add elements of computer control, production automation and control to it.

If this topic is close to you and you are ready to supplement or challenge it, share your opinion, tell us, post descriptions of your decisions in the comment block.

There are several ways to seamlessly connect metal elements, but capacitor welding occupies a special place among all. 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 that allows the metal to melt.

Advantages and disadvantages of technology

The most interesting thing is that capacitor welding can be used not only in industrial environment but also in everyday life. It involves the use of a small-sized apparatus that has a constant voltage charge. Such a device can be easily moved around the working area.

Among the advantages of the technology, it should be noted:

high work productivity;
durability of the equipment used;
the possibility of connecting various metals;
low level of heat release;
no additional consumables;
the accuracy of the connection of elements.

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 the combined elements. In addition, the impulse load is capable of creating various interferences in the network.

Features and specifics of application

The process of joining workpieces 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 heat-affected zone decreases.

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 conventional electrical network. For industrial use, there are special high power devices.

The technology gained particular popularity in workshops intended for body repair. Vehicle. During the work they do not burn through and are not subjected to deformation. The need for additional straightening is eliminated.

Basic process requirements

In order for capacitor welding to be performed at a high quality level, certain conditions must be observed.

The pressure of the contact elements on the workpieces directly at the moment of impulse must be sufficient to ensure a reliable connection. Opening the electrodes should be done with a slight delay, thereby achieving the best mode of crystallization of metal parts.
The surface of the workpieces to be joined must be free of contaminants so that oxide films and rust do not cause too much resistance when the electrical current is applied directly to the workpiece. In the presence of foreign particles, the efficiency of the technology is significantly reduced.
Copper rods are required as electrodes. The diameter of the point in the contact zone must be at least 2-3 times greater than the thickness of the element to be welded.

Technological methods

There are three options for influencing workpieces:

Capacitor spot welding is mainly used to connect parts with different thickness ratios. It is successfully used in the field of electronics and instrumentation.
Roller welding is a certain number of spot joints made in the form of a continuous seam. The electrodes are like rotating coils.
Impact capacitor welding allows you to create elements with a small cross section. Before the collision of the workpieces, an arc discharge is formed, which melts the ends. After the parts come into contact, welding is carried out.

As for the classification according to the equipment used, it is possible to divide the technology by the presence of a transformer. In its absence, the design of the main device is simplified, and the bulk of heat is released in the zone of direct contact. The main advantage of transformer welding is the ability to provide a large amount of energy.

Do-it-yourself capacitor spot welding: a diagram of a simple device

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 fed 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 scheme 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 impulse in this case is generated using a capacitor having a capacitance of 1000 - 2000 microfarads. For the manufacture of a transformer, a Sh-40 core with a thickness of 70 mm can be taken. The primary winding of three hundred turns is easy to make from a 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 bus.

More powerful capacitor welding: diagram and description of a homemade device

To increase the power indicators, it will be necessary to change the design of the manufactured device. 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 with a thickness of not more than 1 mm. To control the signal, a contactless starter marked MTT4K is used, designed for electricity 80 A.

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.

Energy is heated in electrolytic capacitors combined into a single battery by means of the table. You can find the necessary parameters and the number of elements.

The main transformer winding is made of a wire with a cross section of 1.5 mm, and the secondary is made of a copper bus.

The work of a homemade apparatus occurs according to the following scheme. When the start button is pressed, the installed relay is activated, which, using thyristor contacts, turns on the transformer of the welding unit. Shutdown occurs immediately after the capacitors are discharged. The impulse action is adjusted by means of a variable resistor.

Contact block device

The manufactured fixture for capacitor welding should have a convenient welding module that makes it possible to fix and move the electrodes without hindrance. The simplest design involves manual holding of the contact elements. In a more complex version, the lower electrode is fixed in a stationary position.

To do this, on a suitable base, it is fixed with a length of 10 to 20 mm and a cross section of more than 8 mm. The top of the contact is rounded off. The second electrode is attached to a platform that can move. In any case, adjusting screws must be installed, with which additional pressure will be applied to create additional pressure.

It is imperative to isolate the base from the movable platform until the contact of the electrodes.

Work procedure

Before do-it-yourself spot capacitor welding is done, you need to familiarize yourself with the main steps.

At the initial stage, the elements to be connected are prepared properly. Contaminants in the form of dust particles, rust and other substances are removed from their surface. The presence of foreign inclusions will not allow to achieve high-quality docking of workpieces.
Parts are connected to each other in the required position. They should be located between two electrodes. After squeezing, an impulse is applied to the contact elements by pressing the start button.
When the electrical action on the workpiece stops, the electrodes can be moved apart. The finished part is removed. If there is a need, then it is installed at a different point. The thickness of the element to be welded directly affects the size of the gap.

The use of ready-made devices

Work can be carried out using special equipment. This kit usually includes:

apparatus for creating an impulse;
fixture for welding and clamping fasteners;
return cable equipped with two clamps;
collet set;
instructions for use;
wires for connecting to the mains.

Final part

The described technology for connecting metal elements allows not only welding steel products. With its help, you can join parts made of non-ferrous metals without much difficulty. 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: 40% duty cycle - 160 A, 100% duty cycle - 80 A
Welding current regulation limit: 30 A - 160 A

In total, six such devices have been made since 2003. The device, shown below in the photo, has been working since 2003 in a car service and has never been repaired.

Appearance of the semi-automatic welding machine

Generally

Front view

Back view

Left side view

Standard welding wire is used
5kg spool of wire with a diameter of 0.8mm

Welding torch 180 A with Euro plug
was purchased at a welding equipment store.

Scheme and details of the welder

Due to the fact that the semi-automatic circuit was analyzed from such devices as PDG-125, PDG-160, PDG-201 and MIG-180, circuit diagram differs from the circuit board, since the circuit loomed on the fly during the assembly process. Therefore, it is better to stick to the wiring diagram. On the printed circuit board, all points and parts are marked (open in Sprint and hover over the mouse).

Mounting view

Control board

As a power and protection switch, a single-phase automatic machine of the AE type for 16A is used. SA1 - welding mode switch type PKU-3-12-2037 for 5 positions.

Resistors R3, R4 - PEV-25, but they can not be installed (I do not have them). They are designed to quickly discharge inductor capacitors.

Now for the capacitor C7. Paired with a choke, it provides stabilization of combustion and maintenance of the arc. Its minimum capacity should be at least 20,000 microfarads, the optimal one is 30,000 microfarads. Several types of capacitors with smaller dimensions and greater capacity were tried, for example CapXon, Misuda, but they did not show themselves reliably, burned out.

As a result, Soviet capacitors were used, which operate to this day, K50-18 for 10,000 microfarads x 50V, in the amount of three pieces in parallel.

Power thyristors for 200A are taken with a good margin. You can put it on 160 A, but they will work at the limit, 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 wire type PPB.

Pressing the SB1 button on the burner energizes the control circuit. Relay K1 is activated, thereby, through contacts K1-1, voltage is supplied to the solenoid valve EM1 for supplying acid, and K1-2 - to the power supply circuit of the wire pulling motor, and K1-3 - to open power thyristors.

The SA1 switch 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 feed of the welding wire, changes the welding current from 30A to 160A.

When setting, the resistor R12 is selected in such a way that when R10 is unscrewed to a minimum speed, the engine still continues to rotate, and does not stop.

When the SB1 button on the burner is released, the relay releases, the motor stops and the thyristors close, the solenoid valve still remains open due to the charge of the capacitor C2, 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.

We wind the welding transformer

We take the OSM-1 transformer (1kW), disassemble it, put the iron aside, having previously marked it. We make a new coil frame from textolite 2 mm thick (the native frame is too weak). Cheek size 147×106mm. The size of the remaining parts: 2 pcs. 130×70mm and 2 pcs. 87×89mm. In the cheeks we cut out a window measuring 87 × 51.5 mm.
The coil frame is ready.
We are looking for a winding wire with a diameter of 1.8 mm, preferably in reinforced, fiberglass insulation. I took such a wire from the stator coils of a diesel generator). You can also use a conventional enameled wire such as PETV, PEV, etc.

Fiberglass - in my opinion, the best insulation is obtained

We start winding - primary. The primary contains 164 + 15 + 15 + 15 + 15 turns. Between the layers we make insulation from thin fiberglass. Lay the wire as tightly as possible, otherwise it will not fit, but I usually had no problems with this. I took fiberglass from the remains of the same diesel generator. Everything, the primary is ready.

We continue to wind - the secondary. We take an aluminum tire in glass insulation measuring 2.8 × 4.75 mm (you can buy it from wrappers). You need about 8 m, but it is better to have a small margin. We start winding, laying 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, for me personally, for welding large parts at such a voltage, there was not enough current, during operation I rewound the secondary winding, adding 3 turns per shoulder, in total I got 22 + 22.
The winding fits back-to-back, so if you wind it carefully, everything should work out.
If you take enameled wire for the primary, then impregnation with varnish is mandatory, I kept the coil in varnish for 6 hours.

We assemble the transformer, plug it into the socket and measure the no-load current of about 0.5 A, the voltage on the secondary is from 19 to 26 Volts. If so, then the transformer can be put aside, for now we no longer need it.

Instead of OCM-1 for a power transformer, you can take 4 pieces of TS-270, though there are slightly different sizes, and I only made 1 on it welding machine, then I don’t remember the data for winding, but it can be calculated.

We will wind the throttle

We take an OSM-0.4 transformer (400W), we take an enamel wire with a diameter of at least 1.5 mm (I have 1.8). We wind 2 layers with insulation between the layers, lay them tightly. Next, we take an aluminum tire 2.8 × 4.75 mm. and we wind 24 turns, make the free ends of the tire 30 cm each. We assemble the core with a gap of 1 mm (lay pieces of textolite).
The inductor can also be wound on iron from a color tube TV such as TS-270. It only has one coil.

We still have one more transformer to power the control circuit (I took it ready). It should give out 24 volts at a current of about 6A.

Hull and mechanics

With trances sorted out, proceed to the body. The drawings do not show flanges of 20 mm. We weld the corners, all the iron is 1.5 mm. The mechanism base is made of stainless steel.

Motor M is used from the VAZ-2101 wiper.
Removed trailer return to the extreme position.

In the reel, to create a braking force, a spring is used, the first one that came to hand. The braking effect is increased by compressing the spring (i.e., tightening the nut).

Aluminum electrolytic capacitors are one of the main elements that ensure the stability of the high-frequency inverter welding machines. Reliable high-quality capacitors for this type of application are produced by companies,.

The first devices using the arc welding method used adjustable AC transformers. Transformer welding machines are the most popular and are used to this day. They are reliable, easy to maintain, but have a number of disadvantages: high 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 shortcomings by switching to higher current frequencies and reducing the size of the output transformer. The idea to reduce the size of the transformer by switching from the mains frequency of 50 Hz to a higher frequency was born back in the 40s of the XX century. Then it was done with the help of electromagnetic transducers-vibrators. In 1950, for these purposes began to use vacuum tubes - thyratrons. 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 a 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 apparatus as a whole.

Simplified block diagram The inverter can be represented from three blocks (Figure 1). At the input there is a transformerless rectifier with a capacitance connected in parallel, which makes it possible to raise the DC voltage to 300 V. The inverter unit converts direct current 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 two-cycle pulses. In both cases, the transistor block operates in a key mode with the ability to adjust the turn-on time, which allows you to adjust the load current. The output rectifier unit converts the alternating current after the inverter into welding direct current.

The principle of operation of the welding inverter is to gradually convert the mains voltage. First, the mains AC voltage is increased and rectified in the preliminary rectifier unit. The DC voltage powers the high frequency IGBT generator in the inverter unit. The high-frequency alternating voltage is converted to a lower one by means of a transformer and fed to the output rectifier unit. From the rectifier output, current can already be supplied to the welding electrode. The electrode current is controlled by circuitry by controlling the depth of negative feedback. With the development of microprocessor technology, the production of inverter semi-automatic devices began, capable of independently choosing the operating mode and performing such functions as “anti-sticking”, high-frequency arc excitation, arc retention, and others.

Aluminum electrolytic capacitors in welding inverters

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, there are no problems. Due to the fact that the device operates at high frequencies and sufficiently 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 source of a network IP. 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 successively stacked layers of aluminum foil (capacitor anode), paper spacer, another layer of aluminum foil (capacitor cathode), and another layer of paper. All this is rolled up and placed in a sealed container. Conductors are removed from the anode and cathode layers for inclusion in the circuit. Also, aluminum layers are additionally pickled in order to increase their surface area and, accordingly, the capacitance of the capacitor. At the same time, the capacitance of high-voltage capacitors increases by about 20 times, and low-voltage - by 100. In addition, this entire structure is treated with chemicals to achieve the required parameters.

Electrolytic capacitors have a rather complicated structure, which makes them difficult to manufacture and operate. The characteristics of capacitors can vary greatly under different operating modes and climatic operating conditions. With increasing frequency and temperature, the capacitance of the capacitor and ESR decrease. As the temperature drops, the capacitance also drops, and the ESR can increase up to 100 times, which, in turn, reduces the maximum allowable ripple current of the capacitor. The reliability of pulse and input network filter capacitors, first of all, depends on their maximum allowable ripple current. The flowing ripple currents are capable of heating the capacitor, which causes its early failure.

In inverters, the main purpose of electrolytic capacitors is to increase the voltage in the input rectifier and smooth out possible ripples.

Significant problems in the operation of inverters are created by high 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 high pulse currents. All this largely depends on the quality factor of the input filter capacitors, therefore, for inverter welding machines, it is necessary to carefully select the parameters of electrolytic capacitors. Thus, in the preliminary rectification unit of the 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 IGBTs and diodes, which eliminates the influence of the inductance of the wires connecting the device to the power supply on the operation of the inverter. Also, the installation of capacitors near consumers reduces the internal resistance to alternating current of the power supply, which prevents the excitation of amplifying stages.

Typically, the filter capacitor in full-wave converters is chosen so that the rectified voltage ripple does not exceed 5 ... 10 V. It should also be borne in mind that the voltage on the filter capacitors will be 1.41 times higher than at the output of the diode bridge. Thus, if after the diode bridge we get 220 V ripple voltage, then the capacitors will already have 310 V DC voltage. Usually, 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 may have additional heating due to large operating currents. The recommended upper temperature range is at least 85…105°C. Input capacitors for smoothing 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, an increase in the capacitance of the input capacitor proportionally increases the power delivered to the arc.

There are capacities on sale, for example, at 1500 and 2200 microfarads, but, as a rule, instead of one, a capacitor bank is used - several components of the same capacity connected in parallel. Paralleling reduces internal resistance and inductance, 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.

Choice of electrolytes from Hitachi, Samwha, Yageo

In 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 from such world-famous manufacturers of high-quality aluminum capacitors as, and. Companies are actively developing new technologies for the production of capacitors, so their products have the best performance compared to competitors' products.

Aluminum electrolytic capacitors are available in several form factors:

for PCB mounting;
with reinforced snap-in terminals (Snap-In);
with screw terminals (Screw Terminal).

Tables 1, 2 and 3 present the series of the above manufacturers, the most optimal for use in the preliminary rectifier unit, and their appearance shown in figures 2, 3 and 4, respectively. The given series have maximum term service (within a specific manufacturer's family) and extended temperature range.

Table 1 Yageo Electrolytic Capacitors

Table 2. Samwha Electrolytic Capacitors

Table 3. Hitachi Electrolytic Capacitors

Name	Capacitance, uF	Voltage, V	Ripple current, A	Dimensions, mm	Form Factor	Service life, h/°C
	470…2100	400, 420, 450, 500	2,75…9,58	30×40, 35×35…40×110	Snap-in	6000/85
	470…1500	400, 420, 450, 500	2,17…4,32	35×45, 40×41…40×101	Snap-in	6000/105
	470…1000	400, 420, 450, 500	1,92…3,48	35×40, 30×50…35×80	Snap-in	12000/105
	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. Hitachi capacitors with a guaranteed service life of up to 12,000 hours seem to be the most reliable, 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 capacitors. True, this parameter does not indicate a guaranteed failure of the capacitor after the specified line has elapsed. This refers only to 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 line, it is also possible to reduce the capacity by 10% and increase losses by 10 ... 13% when operating at maximum temperature.

Developed in the 1930s, capacitor welding technology has become widespread. A number of factors contributed to this.

The simplicity of the design of the welding machine. If desired, it can be assembled by hand.
Relatively low energy consumption of the working process and low loads created on the electrical network.
High productivity, which, of course, is important in the production of serial products.
Reducing the thermal effect on the joined materials. This feature of the technology makes it possible to use it when welding small parts, as well as on specific surfaces, where the use of conventional methods would inevitably lead to undesirable deformations of the material.

If we add to this that it is enough to have an average level of skill to apply high-quality connecting seams, the reasons for the popularity of this resistance welding method become obvious.

The technology is based on the contact welding. The difference is that the current is supplied to the welding electrode not continuously, but in the form of a short and powerful pulse. This impulse is obtained by installing high-capacity capacitors in the equipment. As a result, it is possible to achieve good performance of two important parameters.

Short time of thermal heating of connected details. This feature is successfully used by manufacturers of electronic components. Transformerless installations are best suited for this.
High current power, which is much more important for the quality of the seam than its voltage. This power is obtained using transformer systems.

Depending on the requirements of production, one of three technological methods is chosen.

Spot capacitor welding. Using a short pulse of current emitted by a capacitor, they connect parts in precision engineering, electrovacuum and electronic technology. This technology is also suitable for welding parts that differ significantly in thickness.
Roller seam allows you to get a completely tight connection, consisting of many overlapping welding points. This leads to the use of technology in the manufacturing process of electrovacuum, membrane and bellows devices.
Butt welding, which can be performed both by contact and non-contact methods. In both cases, melting occurs at the junction of the parts.

Application area

The areas of application of the technology are different, but with particular success it is used for fastening bushings, studs and other fasteners to sheet metal. Given the characteristics of the process, it can be adapted to the needs of many industries.

Automotive industry, where it is necessary to securely interconnect body panels made of sheet steel.
Aircraft industry, which places special demands on the strength of welds.
Shipbuilding, where, taking into account the large volume of work, saving electricity and consumables gives a particularly tangible result.
Production of precision instruments, where significant deformations of the connected parts are unacceptable.
Construction, in which sheet metal structures are widely used.

Easy-to-device and easy-to-use equipment is in demand everywhere. With it, you can set up the production of small-scale products or equip a personal plot.

Homemade capacitor welding

In stores, you can easily purchase ready-made equipment. But due to the simplicity of its design, as well as the low cost and availability of materials, many people prefer to assemble devices for capacitor welding with their own hands. The desire to save money is understandable, but to discover online desired scheme and detailed description possible without difficulty. Such a device works as follows:

The current is directed through the primary winding of the supply transformer and the rectifying diode bridge.
The control signal of a thyristor equipped with a start button is applied to the diagonal of the bridge.
A capacitor is built into the thyristor circuit, which serves to accumulate the welding pulse. This capacitor is also connected to the diagonal of the diode bridge and connected to the primary winding of the transformer coil.
When the device is connected, the capacitor accumulates a charge, being powered from the auxiliary network. When the button is pressed, this charge rushes through the resistor and the auxiliary thyristor towards the welding electrode. The auxiliary network is switched off.
To re-charge the capacitor, you need to release the button, opening the resistor and thyristor circuit and reconnecting the auxiliary network.

The duration of the current pulse is controlled by a control resistor.

This is only a basic description of the operation of the simplest equipment for capacitor welding, the device of which can be changed, depending on the tasks being solved and the required output characteristics.

Need to know

Anyone who decides to assemble their welding machine on their own should pay attention to the following points:

The recommended capacitance of the capacitor should be about 1000 - 2000 microfarads.
For the manufacture of a transformer, the core of the Sh40 variety is best suited. Its optimal thickness is 70 mm.
The parameters of the primary winding are 300 turns of copper wire with a diameter of 8 mm.
The parameters of the secondary winding are 10 turns of a copper bus with a cross section of 20 square millimeters.
The PTL-50 thyristor is well suited for control.
The input voltage must be provided by a transformer with a power of at least 10 W and an output voltage of 15 V.

Based on these data, it is possible to assemble a fully functional spot welding device. And although it will not be as perfect and convenient as factory-made equipment, with its help it will be quite possible to master the basics of the profession of a welder and even begin to manufacture various parts.