How to connect capacitors to welding. Bringing to mind the budget semi-automatic. Electrolytic capacitors in welding inverters

Aluminum electrolytic capacitors are one of the main elements that ensure the stability of 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 machines 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 a high capacitance, high voltage rating, small size, 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 pulsating 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 is 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. 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 JY series Samwha 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.

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

At all

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 OSM-1 for a power transformer, you can take 4 pieces of TC-270, although there are slightly different sizes, and I only made 1 welding machine on it, 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).

I bought my transformer semiautomatic device. Well, I thought it would be enough for me for a long time, since I planned it for welding and repairing car bodies. As a result, I was disappointed that he simply burned thin metal at the moment the welding wire touched the surface to be welded. And he simply did not boil the thick metal about 4 mm thick as it should.

As a result, I just wanted to throw it away. You can’t carry it back to the store, since a lot of time has passed, and I have more than one job. So it was decided to assemble an inverter for my device in order to get rid of the transformer that worked, it’s not clear how.

The diagram itself is shown in the figure. This circuit was taken from the basis of a 250 amp welding inverter, which was developed by Evgeny Rodikov. For which we thank him.

True, I had to pretty tinker with this circuit so that an ordinary welding inverter with a soft CVC (voltage characteristic) becomes rigid and that there is voltage feedback and can be adjusted from 7 volts to 25 volts. Since the semiautomatic device does not need to regulate the current, it needs to change the voltage. Which is what I did.

First we need to assemble a power supply that will power the PWM generator and key drivers.

That's actually the power supply circuit, it's not complicated and I think I won't go into details, and everything is clear.

The principle of operation of the inverter

The operation of the inverter is as follows. From the network, 220 volts enters the diode bridge and is rectified, then high-capacity capacitors are charged through the current-limiting resistor R11. If it were not for the resistor, then a strong bang would occur due to which the diode bridge would fail. When the capacitors are charged, the timer on VT1, C6, R9, VD7 turns on relay K1, thereby shunting the current-limiting resistor R11 and the voltage at this time on the capacitors rises to 310 volts. and at the same time, relay K2 turns on, which opens the circuit of resistor R10, which blocks the operation of the PWM generator assembled on the UC3845 chip. The signal from the 6th leg of the PWM generator is fed to optocouplers through resistors R12, R13. Then passing through the HCPL3120 optocouplers to the power IGBT control drivers that drive the power transformer. After the transformer, a large high-frequency current comes out and enters the diodes, thereby rectifying. Voltage and current control is performed on the PC817 optocoupler and a current sensor built on a ferrite ring through which the power transformer wire is passed.

Start assembly work of the inverter

The assembly itself can be started anywhere. I personally started collecting from the power supply itself, which should power the PWM generator and key drivers. After checking the performance of the power supply, it worked for me without any modifications and settings. The next step, I assembled a timer that should block the PWM generator and shunt the current-limiting resistor R11, making sure it works, it should turn on the K1 and K2 relays for a period of 5 seconds to 15 seconds. If the timer runs faster than necessary, then you need to increase the capacitance of the capacitor C6. After that, I started assembling the PWM generator and the power switch driver in the PWM generator, there is one flaw with the resistors R7, it should have a resistance of 680 Ohm R8 1.8 Ohm and a capacitor C5 510p C3 2200p, who also made sure that the assembly was correct, set the initial frequency to 50 kHz using a resistor R1. In this case, the signal generated by the PWM generator must be strictly rectangular 50/50 and no bursts or spikes from the edges of the rectangles shown on the oscilloscope waveform. After I assembled the power keys and applied a voltage of minus 310 volts to the lower power keys. plus the upper power switches, I supplied power plus 310 volts through a 220 volt 200 watt bulb on the circuit itself is not shown, but it is necessary to add 0.15 microfarad x 1000 volt capacitors 14 pieces to the power switches plus and minus 310 volts. this is necessary in order for the emissions that the transformer will create to go into the power circuit of the power switches, eliminating interference in the 220 volt network. After that, I began to assemble a power transformer, and it all started like this for me. I don’t know what ferrite material I wound a test winding, for example, 12 turns of copper wire 0.7 mm in diameter, varnished, turned it on between the arms of the power switches and started the circuit, making sure that the light bulb was lit at the glow floor a little bit, after waiting about 5 or 10 minutes, I turned off the circuit from the outlet let the filter capacitors discharge so that the current does not knock, check the core of the power trance itself, it should not heat up. If it got hot, I increased the number of windings and thus I reached 18 turns. And so I wound the transformer with the calculation of the sections that are written on the diagram.

Setting up and starting the inverter for the first time

Before setting up and the first start-up, we check again in the correct assembly. We are convinced of the correct phasing of the power transformer and the current sensor on a small ring. The current sensor usually selects the number of turns of the wire, the more turns the greater the output current, but do not neglect the fact that you can overload the power switches and they can easily fail. In this case, if you do not know the ferrite material, it is best to start with 67 turns and gradually increase the number of turns until the arc is sufficiently hard when welding. For example, I got 80 turns, while the network does not load, the power switches do not heat up, and naturally there is no noise from the power transformer and the output choke.

And so we begin the first start-up and setup with the light bulb turned on as described above, while a bunch of capacitors of 14 pieces of 0.15 microfarads must be included to power the keys plus and minus 310 volts. turn on the oscilloscope to the emitter and collector of the lower arm of the power switches. Before that, we do not hook the voltage feedback optocoupler, temporarily leave it hanging in the air on the oscilloscope, there should be a rectangular frequency signal, we take a screwdriver and twist the resistor R1 until a small bend appears at the bottom corner of the rectangle. Turn in the direction of decreasing frequency. This will indicate a supersaturation of the core of the power transformer. When bending at the received frequency, write it down and calculate the operating frequency of the power transformer core. For example, the oversaturation frequency is 30 kHz, we consider 30 divided by 2, we get 15, the resulting number is added to the oversaturation frequency 30 plus 15, we get 45. 45 kHz is our operating frequency. In this case, the light bulb should glow almost imperceptibly dimly. current consumption should not exceed 300 mA at full idle, typically 150 mA. look at the oscilloscope so that there are no voltage spikes above 400 volts, usually 320 volts. As everything is ready, we hook a kettle or a heater or an iron of 2000 watts to the light bulb. We hook a decent-sized wire to the output, for example, from 5 squares of 2 meters we make a short circuit, while the light bulb should not burn at full brightness, it should glow a little more than half the glow. If it glows at full brightness, then you need to check the current sensor in phasing again, just skip the wire on the other side. In extreme measures, reduce the number of turns on the current sensor. After everything is ready, now plus the 310 volt power supply, let it go straight without a light bulb and a 2000 watt heater. Do not forget about the cooling of power keys, a radiator with a fan is best suited for a radiator from an old-style computer Intel Pentium or AMD Atom. The power switches must be screwed onto the heatsink without a mica gasket and through a thin layer of KPT8 thermally conductive paste to ensure maximum cooling efficiency. The radiator must be made separately from the upper and lower arms of the half-bridge. Snubber diodes and diodes connected between the power supply and the transformer should be placed on the same radiators as the keys, but through a mica gasket in order to avoid a short circuit. All capacitors on the PWM generator must be exactly film capacitors with the inscription NPF, so you will avoid unpleasant moments under weather conditions. Capacitors on snubbers and output diodes should be strictly only of the K78-2 or SVV81 type, and no rubbish should be put there, since snubbers play an important role in this system and they absorb all the negative energy that the power transformer creates.

The start button for the semi-automatic device that is located on the burner sleeve must be made into a break in the overheating temperature sensor. And I almost forgot at the output of the power transformer when you set up the entire system without a feedback optocoupler, the 220uF capacitor must also be temporarily removed so as not to exceed the output voltage and at the same time at the output in this scenario, the voltage should be no more than 55 volts; if it reaches 100 volts or more, it is desirable to reduce the number of turns, for example, unwind 2 turns to get the voltage we need, after that you can put a capacitor and a feedback optocoupler. Resistor R55 is a voltage regulator R56, a maximum voltage limiting resistor, it is better to solder it in the board next to where the optocoupler is to avoid a jump when the regulator breaks and select it in the direction of increasing resistance to the desired maximum current, for example, I did up to 27 volts. Resistor R57 adjustable for a screwdriver to adjust the minimum voltage for example 7 volts.

The device that we will present in this article is called “capacitor welding”. This welding can connect very small or thin objects and parts. Its difference from standard spot welding is that the heating of the junction 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 construction is 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 to the capacitance, which, if necessary, can be replaced with a conventional resistance equal to 10 kOhm. After the 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 goes out, it means that the capacitor bank is fully charged. After that, it's ready to go. The discharge is switched on by pressing the button built into the holder. Such welding allows you to weld not only thin plates, but also studs of different diameters to metal surfaces. To do this, it is possible to hold the pin in the holder.

Discussion

Urnfra yovlya
+azim meex Have you ever touched the leads of a charged capacitor at 3.8 microfarads 250 V? At the beginning of the video, it was said: 30,000 microfarads, the voltage is 70 volts, as a result we get 73.5 joules, this is at least. The range of 10-50 J per impulse is already losing its non-lethality, and can cause electrical injuries that are incompatible with life (cardiac fibrillation, death).

Urnfra yovlya
+azim meex
70 volts is the minimum voltage for the capacitor, since it feeds from 70. And what about the drop? You check, and then tell me about the ways of its flow.

Alexey Grachev
+toyama tokanava in a damp room with lots of metal appliances around? Moreover, the voltage is probably indicated not constant, but variable, right? No, if you wish, you can kill yourself with 12 volts, but I haven’t met such people. And then, almost all transformer welding operates at a voltage of about 70 volts and there are no special problems.

toyama tokanava
I don't even mind, but there are certain rules to use, speaking as a former welder and former electrician. The safety rules are here to help.

Vladimir lokot
+ alexey grachev a fully charged capacitor of a hundred times less capacity when discharged through a finger makes 2 burnt holes in it, quite deep by the way, this is basically not fatal, but damn painful. I don’t even know what to compare with - much more painful than a wasp sting, for example. But what “holes” this fool will burn, I honestly am afraid to imagine.

Alexey Grachev
+ vladimir lokot so everything depends on the voltage. You can charge a hundred farads at 30 volts and only pinch on contact with your finger, or you can charge one microfarad with a thousand volts and then it won’t seem enough, there will be holes and anything. Ohm's law be damned.

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. More than once I felt this voltage on myself, as I regularly cook with both alternating and direct current, in the latter case through a diode bridge and capacitors. Notably, 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 is not willing to argue with you, but 70 volts from a welder is garbage compared to the instantaneous discharge of a capacitor bank of good capacity; even 220v from a power outlet is bullshit. And Ohm's law, which you mentioned 2 times in vain here, perfectly describes why, if you think a little. With the instantaneous discharge of such a capacitor, 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 a resistance in fact), 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 the capacitor at least 50-100 microfarads 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. There are people out there who twist wires 220 holding on to 2 wires and it only pinches out of it. Or which the police stun gun is completely ignored. But these are rather exceptions.

Alexey Grachev
+ vladimir lokot a few messages above, I already wrote about the presence of welding with capacitors. The fact that 70 volts beat noticeably does not prove anything. Farewell.

Sergeypn
Dangerous. You can hit someone on the head with all this crap and it will be bad. And so nothing dangerous, why grind with your tongue what we don’t understand.

Sapar malikov
I constantly repair amplifiers there +/-100 volts DC and capacitors for modern amplifiers are at least 4 pieces of 10,000 microfarads per 100 volts, sometimes we forget to discharge the capacitors with a current, it will hit hard, of course, but there will be no holes, all the more so, the stay is not very harmful to life

alexander developer
50 or 100? It's like a twofold difference. Of course, everyone has it differently, but I calmly held on to the terminals of the laboratory power supply unit when it was 90. I was then 13 years old and nothing. (Of course, I don’t advise you to repeat it, especially if the power supply unit is without current protection, or even more so if the power supply unit is an impulse switch. Or you are standing barefoot on a metal floor). On the topic - I definitely don’t understand why there is a 70th century. I think that when discharging, the capacitors switch to a parallel connection - the capacitance and discharge current increase while the voltage drops. In addition, the charge there is limited and, according to the idea, these 70 volts that come should go through a galvanic isolation (transformer) - if you stand barefoot on metal and do not attach or poorly attach a second electrode, it can shock, but definitely not kill.

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 like this.
If we exclude the diode between 1 and 2 and the jumper between 3 and 4, then a diode bridge can be inserted. Hint as below picture. Too lazy to draw 2 trains the same.
Part numbers must be considered. Under specific conditions.
A literate person will figure it out, but a literate person in a different area of ​​​​skills will pay a literate person in electronics and electricity.)
The logic of work.
1. Turned on in 220 all switches are open.
2. We closed kn 1 and wait for the charging current to stop (the lamp went out).
3. Opened kn 1, briefly closed (or hold) kn 2. We weld the part.
4. Opened kn 2.
If where I made an inaccuracy, then I think Alexander will correct me.

Sergey psg
+ Dim Russ I have not done yet.
The author in the video says the capacitance of capacitors is 30 thousand microfarads. The voltage on the bridge is 70 volts \u003d on capacitors 100-110 volts. The capacitors themselves must be taken for a higher voltage of 125-160 volts. 160 is even better. I don't remember the voltage range for the capacitors. Is it possible to answer more or less only practice can answer. Put the container more possible to burn the surface to be welded (burn through), forgive me welders. Put less, not enough energy for the process. Can the voltage be less? Yes you can, but! If my memory does not change 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 conduits * 30 thousand microfarads. And then if something does not suit you, select the parameters for yourself. For welding the output to the battery is one thing, but it is more powerful to use it in auto straightening.

Evgeny Fedorov
Useful information! I don't have any electronics contact welding, though the button is through the thyristor on the primary. For small thicknesses the timer. I weld plates with a thickness of 01 to 1.5 mm.

azim meex
+vahe vardanyan firstly, the powder will inflate the hands and face of the welder, secondly, graphite will carbonize the point (not the seam) of the welding, which will make it more brittle and thirdly, it will reduce the resistance of the welding spot 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 is melted at points with minimal resistance, that is, at places pressed by electrodes. The energy of the capacitor is e \u003d c * u * u / 2, from which it follows 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 able to deliver a large current during a short circuit, and it can quickly become unusable. Therefore, from a battery of parallel capacitors we will get a noticeably greater current than from one if it had a capacity like the entire battery.

Valery Lysenko
+ sergey psg if it's easy for you, then draw a diagram. Take a screenshot or a photo of this sheet and put it on the social network. Send us the link. So as not to talk with the tongue that it's simple. I'll take a look at the diagram.

Petrow60
good health. Very interesting topic, if it would be possible to publish the schematic with the parameters. This video deserves like and respect. Thanks. Looking forward to continuing as a subscriber.

Toyama tokanava
If you add a pulse current transformer at the output with a ratio of turns of one to ten, you can get ten times the current at the electrodes. The cross section of the wires of the windings should be taken according to the current in them, the number of turns does not even need to be large, so take ten turns and the secondary one turn. I even think you can cook rebar. I had to repair a welding plant in a fittings shop, they used a mercury rectifier of about 1000 volts and oil capacitors of 100 microfarads, and the thyristor control is almost the same as yours.

Denis
Dear video author! I do welding like yours. I use an ea-ii-10 capacitor with a nominal value of 33000 microfarads, a voltage of 63V and a T-160 thyristor. I charge the capacitor with a power supply.
From the “+” of the capacitor there is a wire 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 the micro switch. The thyristor is working, checked, the capacitor too. For some reason, the thyristor does not open instantly (when the thyristor is opened, the voltmeter needle slowly starts to go to zero) and welding does not occur. Please tell me what could be the problem? Thanks in advance.

Sungazer
+ denis is put on Well, firstly, the thyristor is a powerful, but slow thing.
And secondly, the electrolyte conder is not designed for high currents.
Therefore, during prolonged operation, the conder will overheat. Therefore, it is better to dial conders with a small denomination and parallelize.

Yury galinsh
+sungazer how to understand “slow stuff”? In network power regulators, at a frequency of 50 Hz, a thyristor (semistor) fires 50 (or 100) times per second. Moreover, he “cuts off” the sinusoid almost vertically. In a specific case, this is an ordinary switch.
The electrolytic capacitor drops, if I'm not mistaken, 80% of the capacity in milliseconds.
I can assume a malfunction of the thyristor itself. And as far as I remember, a current limiter (resistor) was placed to the control electrode. Well, the capacitor can smoothly discharge through the control electrode.

Alexander polyakh
You need to look for components on the radio markets or order on the Internet. Everything is. The larger the capacitance of the capacitors, the greater the charge will be. The micro switch sends micro currents to the thyristor and it instantly releases the entire impulse of the stored energy of the capacitors.

User0011
+ Anton Tunov look at scrap metal collection points! They don’t go to scrap aluminum, they don’t take thin scrap metal and aluminum foil! Therefore, you can buy at the price of ferrous metal. No need to overpay somewhere in the markets! And if you are interested in receivers (etc.). Here is such a “barrel” so many, but such is so much. That can be picked up quickly.

Got into my hands Chinese semi-automatic welding Vita (hereinafter I will simply call it PA), in which the power transformer burned out, my friends just asked me to repair it.

They complained that when they were still working, it was impossible for them to cook something, strong splashes, crackling, etc. So I decided to bring him to the senses, and at the same time share my experience, maybe someone will come in handy. At the first inspection, I realized that the transformer for the PA was not wound correctly, since the primary and secondary windings were wound separately, the photo shows that only the secondary remained, and the primary was wound nearby (this is how the transformer was brought to me).

And this means that such a transformer has a steeply falling CVC (voltage characteristic) and is suitable for arc welding, but not for PA. For Pa, a transformer with a rigid IV characteristic is needed, and for this, the secondary winding of the transformer must be wound on top of the primary winding.

In order to start rewinding the transformer, you need to carefully unwind the secondary winding without damaging the insulation, and cut down the partition separating the two windings.

For the primary winding, I will use a copper enamel wire 2 mm thick, for a complete rewind, 3.1 kg of copper wire, or 115 meters, will be enough for us. We wind a coil to a coil from one side to the other and back. We need to wind 234 turns - this is 7 layers, after winding we make a tap.

We isolate the primary winding and taps with cloth tape. Then we wind the secondary winding with the wire that we unwound earlier. We wind tightly 36 turns, with a shank of 20 mm2, approximately 17 meters.

The transformer is ready, now let's deal with the throttle. The throttle is an equally important part in the PA without which it will not work properly. It was made incorrectly, because it does not have a gap between the two parts of the magnetic circuit. I will wind the inductor on iron from the TS-270 transformer. We disassemble the transformer and take only the magnetic circuit from it. We wind a wire of the same cross section as on the secondary winding of the transformer on one roll of the magnetic circuit, or on two, connecting the ends in series, as you like. The most important thing in the throttle is a non-magnetic gap, which should be between the two halves of the magnetic circuit, this is achieved by textolite inserts. The thickness of the gasket ranges from 1.5 to 2 mm, and is determined experimentally for each case separately.

For more stable arcing, capacitors with a capacity of 20,000 to 40,000 microfarads must be placed in the circuit, and the voltage of the capacitors must be from 50 volts. Schematically, it looks like this.

In order for your PA to work normally, it will be enough to do the above actions.
And for those who are annoyed by the direct current on the burner, you need to put a 160-200 ampere thyristor in the circuit, see how to do this in the video.

Thank you all for your attention -)