What is the voltage in the welding machine - Metals and their processing

Voltage stabilizer for welding inverter

Many welders experience network sagging. When you urgently need to finish a job, you have to change the diameter of the electrodes, switch from 4 to 3. It is clear that it will no longer be possible to thoroughly weld a deep seam.

With a voltage stabilizer for a welding machine, fluctuations in the parameters of the power supply network are not terrible. The device supplies current with the required voltage. The welding becomes uniform. Choosing a stabilizer is not easy. Manufacturers offer a large selection. Experts will tell you what criteria to pay attention to.

Design and principle of operation

Often a decrease in voltage is recorded in the private sector and densely populated urban areas. The surges are associated with the simultaneous connection of household heating appliances. The stabilizer is designed to protect against significant fluctuations in the network and maintains the power required for the welding arc.

It is no coincidence that the second name for a voltage stabilizer for welding is an electric arc stabilizer. The stabilizing effect is based on the effect of magnetic induction.

The equipment is similar to a transformer: the electric field of the first coil generates an inductive or induced current in the second winding, connected in a single circuit with the welding machine.

When the voltage drops to a critical level (180 V) in the first winding, a reactive coil is connected in the secondary circuit. It supplies a compensating charge. The number of connected turns is proportional to the voltage drop.

When the network is 240 V (such fluctuations also happen), the regulator automatically reduces the number of turns of the secondary winding. There is again a stable signal at the output of the supply circuit.

Stabilizing equipment turns on only when the input signal decreases or increases. Connecting additional turns will prevent the electric arc from dying out during the welding process. Voltage stabilization occurs automatically without the participation of a welder.

The principle of electronic stabilizing devices is more complex; semiconductors and capacitors are involved. Due to the converter circuits, energy losses are compensated; the input current indicators do not affect the output voltage or amperage. Similar stabilizers are built into powerful inverters. Professional welding equipment does not require external protection.

Short.

The voltage stabilizer maintains the required voltage during power surges, which allows you to use the welding machine to its fullest potential. In dacha cooperatives, voltage drop in the network is a common problem. This is where a voltage stabilizer comes to the rescue.

Technical parameters of stabilizers

The characteristics of the stabilizing devices must correspond to the welding equipment. A classification of stabilizers for welding according to their intended purpose has been developed. Equipment produced:

maintaining a transformer welding machine in working condition;
configured for semi-automatic;
working with devices with inverter type converters.

Source: https://svarkaprosto.ru/oborudovanie/stabilizator-napryazheniya-dlya-svarochnogo-invertora

How does an inverter welding machine work?

Increasingly, not transformer welding machines, but inverter ones are being used for welding. They don't leak through the net and are easier to cook with. This is due to the fact that the design of an inverter welding machine differs significantly from a transformer welding machine.

Why is a welding inverter better than a transformer?

Let's start with what an inverter welding machine is. This is a device for manual or semi-automatic welding, operating from mains voltage. There are devices that connect to a 220 V network, and there are 380 V ones. Regardless of the number of phases, the welding current (which goes to the electrode) is constant. So it is easier to weld with an inverter welding machine - the arc is stable and does not jump. In addition, there are options such as “anti-sticking” and overheating protection. But these are not all its advantages.

An inverter welding machine is much smaller and lighter than a transformer one. This is important, especially if you need to drag it around the site. Another advantage is that it does not “jam” the network and does not “give” voltage surges.

What is the matter, what is the difference between an inverter device and a transformer device? The whole secret is triple voltage conversion. First, the alternating voltage is converted into direct voltage, and then again into alternating voltage, but at a very high frequency. It is then converted back to direct current in a secondary rectifier. It is used in welding. This is, in brief, the principle of operation of a welding inverter.

Thanks to modern circuitry, high-quality welding inverters are highly reliable.

How an inverter welding machine works: block diagram

The schematic diagrams of inverter welders from different companies differ, as does the element base. But they all consist of the same blocks, since the principle of operation is the same for all.

In the primary LF (low frequency) rectifier, the mains voltage is converted to DC, which is supplied to the inverter input. The inverter converts direct voltage with a frequency of 50 Hz into alternating voltage of high frequency (tens of kHz).

A high-frequency transformer lowers the voltage and increases the current, which can exceed 250 A. This is the current needed when welding.

The secondary rectifier converts alternating voltage to direct voltage, and the inductor completes the conversion and direct current flows to the electrode.

Block diagram of an inverter welding machine

This is the general working principle of inverter welding machine. As you can see, it is called that because the inverter is the key element of the circuit.

An inverter is a device for converting direct current into alternating current by changing the voltage value. Usually it is a generator of periodic voltage, in shape close to a sinusoid, or a discrete signal.

Most inverter welding machines also have controllers and devices for maintaining specified parameters. They are usually based on processors, although there are also electromechanical models.

Why are all these transformations needed and why is the inverter welding machine so small and light

Why are there so many stages of transformation? In order to obtain an output current of hundreds of amperes and not overload the electrical network. The second task is to obtain a constant current, since it is easier to cook on a constant current. The arc is stable and easier to control.

In the simplest transformer welding machines, rectification occurred on the transformer and, after some stabilization (several capacitors), immediately went to the electrode. To convert mains voltage with a frequency of 50 Hz, a large transformer is required, since the diameter of the wire must be large. And this determined the size of the device itself and its weight.

Operating principle of a welding inverter: voltage and current conversion stages

In inverters, through transformations, the frequency is increased to several tens of kilohertz (maybe 50-80 kHz) and after that it is converted to constant. High frequency alternating voltage is converted to direct voltage using a small transformer. It is several times smaller and lighter.

This is why inverter welders are so compact and lightweight. But since there are many stages of conversion, control and coordination of the operation of all blocks is required. Therefore, inverter welding machines, with their small size and weight, cost more. At least there seems to be a saving in materials.

But the fact is that there are also controllers that cost a lot.

Welding inverter design: description of operation and purpose of blocks based on the RESANTA SAI 140 circuit

Each manufacturer has different circuit diagrams for inverter welding machines. Moreover, even different lines of the same manufacturer can differ significantly. But the design of the welding inverter has common features. The blocks are the same.

They can just be assembled differently.

This is an input rectifier based on a powerful diode bridge and smoothing capacitors, an inverter based on key transistors (IGBT or MOSFET type) and an output rectifier based on a high-frequency step-down transformer and a diode bridge with an output capacitor filter.

Schematic diagram of the inverter welding machine RESANTA SAI 140

Next, let's look at how the welding machine works, based on the diagram of the inverter welding machine RESANTA SAI 140. It is no better or worse than the others, it just has its diagrams.

Primary rectifier and capacitor filter

The primary rectifier's job is to convert a 50 Hz sine wave into direct current. In reality, it turns out not to be completely constant, but with some pulsation, but this is clearly not a sinusoid. This is realized by a conventional diode bridge, which “inverts” the lower half-wave of the sine wave.

How a welding inverter works: the first stage of voltage conversion in Resanta SAI 140

The mains voltage passes through the input stabilizing group to capacitors C1 and C2. The main task is to relieve static voltage on the ground. That is why it is highly advisable to turn on inverter welding into an outlet with a functioning grounding, and not just with an existing contact.

Next, the diode bridge “turns over” the lower half-wave. Its output produces a pulsating voltage. To smooth out ripples, capacitors are installed (in the diagram above, this is capacitor C8 with a capacity of 1 microfarad for a voltage of 400 V).

At their output the voltage is already constant. The capacitors have a significant voltage reserve - 400 Volts and higher, since at the output of the diode bridge the voltage is already greater than the mains voltage - about 320-350 V.

And if we take into account possible surges, they set it with a margin - at 400 V.

Both capacitors and diodes get very hot during operation. For better heat dissipation, they are mounted on aluminum radiators. Often they also provide additional airflow by installing a fan. If you want your welding machine to last a long time, make sure that the cooler is in working order.

Inverter

The inverter unit converts low-frequency rectified DC voltage into high-frequency AC voltage. It is usually implemented on key transistors, which open and close with high frequency. They form an alternating voltage with a frequency of tens of kilohertz. The controller controls their switching.

Power transistors G30N60, with the help of which direct current is converted into high-frequency alternating current

G30N60 is an insulated gate bipolar transistor (IGBTs).

At the output of the inverter we receive not a sine wave, but almost rectangular pulses. But for further straightening this is not a problem. But the frequency is high, which means that the secondary rectifier can be made on a small-sized transformer.

Straightening and stabilization

The resulting high-frequency voltage is supplied to a high-frequency transformer. The voltage across it decreases, the current increases. A high voltage of low current flows through its primary winding, and a lower voltage is removed from the secondary winding, but the current is already about 150-220 amperes - depending on the power and class of the device.

Output voltage conversion before applying to the electrode

To obtain a constant voltage, there is a diode bridge at the output of the transformer. It produces an almost constant voltage, which is “smoothed” by the output capacitors and goes to the welding electrode.

The diodes on the output bridge are special - with a high response speed (no more than 40-55 nanoseconds). They must smooth out voltages with a frequency of tens of kilohertz, so the response speed must be very high.

If during the repair process there is a need to replace them, then it is necessary to select one with high performance. Otherwise the device will not work.

Source: https://elektroznatok.ru/tools/ustrojstvo-svarochnogo-invertora

Welding inverter for reduced voltage

The provision of stable network power in cities and rural areas is fundamentally different. The use of modern household appliances with their high energy consumption has placed villages and holiday villages in conditions of equipment operating at low voltages in the public network.

Any construction involves the use of metal compounds, so welding inverters operating at low network voltages will always be in demand far from cities.

We will look at models of inverter devices operating in these conditions and ways to ensure their optimal performance.

Operating principle of a welding inverter

The principle of operation of the inverter is based on the conversion of input alternating current with a frequency of 50 Hz and a voltage of 220/380 V into an output current of increased power. It provides a short circuit arc, as a result of which the metal melts at the junction of the parts.

The equipment that achieves a stable arc effect is a welding machine. In the case of reduced input characteristics, it acts as a welding inverter operating at low supply voltages.

These units are no different from conventional ones, except for the circuit design and the semiconductor elements used.

Devices for low voltage are characterized by a small influence of input parameters on the process caused by welding of parts. This occurs due to the fact that the built-in voltage stabilizer for the welding inverter operates, which smoothes out surges. Any inverter uses the output voltage to convert it into a powerful welding current in order to fuse metals into one whole in composition and strength characteristics. These units consist of the following blocks:

low-frequency rectifier that converts alternating voltage 220/380 V into direct current;
high-frequency transistor inverter that generates alternating current with a high oscillation frequency;
power transformer with a choke, which allows you to supply welding current to the inverter terminal;
a feedback system that regulates the output current, arc ignition, and stabilizes the output voltage;
optionally there is a rectifier, arc forcing and an anti-stick electrode function;
system of indication and control of operating modes, system of ventilation and protection from extreme welding conditions.

Ensuring efficient inverter operation

Fluctuations in indicators in public power networks can be from 150 V to 270 V, with a rated power supply of 220 V. This occurs due to load imbalance between phases and outdated equipment, which does not have the ability to regulate stable parameters in the network. This situation is typical for rural areas and, unfortunately, is widespread. To ensure the operation of the welding inverter in such conditions, the following circumstances are necessary:

the presence of an input voltage stabilizer for the welding machine, which must provide the power necessary for operation;
engineering circuit solutions that allow the unit to perform its functions in conditions of changes in network values;
the presence of a welding oscillator for effective ignition of a short circuit arc;
selection of device parameters that provide optimal open circuit voltage for the welding inverter.

The input voltage stabilizer must provide power consumption ranging from 5 kW to 9.8 kW and operate in a wide range of surges in AC supply currents.

It should be noted that large dimensions, weight and high price do not make this equipment particularly popular.

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Therefore, the most popular are power supply stabilizers built into the inverter, which make it possible to reduce network instability by selecting semiconductor elements and their operating modes.

In the model range of many manufacturers there is no such device that cannot operate at least in the range from 190 to 230 V, and some units designed for the Russian market operate in a much wider range of input indicators.

Since stabilizers for inverters are too expensive, when choosing a device you should focus on circuit solutions and high-quality components.

It is necessary to ensure the presence of an oscillator, as well as the stability of the open circuit voltage during surges in the network.

Recommended inverters for low power operation

There are German, Italian, Chinese and Russian devices on the inverter market that can stably perform their functions both when network parameters increase and decrease. We will look at some models in the budget and mid-price categories, which have the following qualities:

wide limits of welding current adjustment;
the presence of a hot start function;
possibility of operation within a wide temperature range;
continuous operation at maximum current;
stable open circuit voltage;
operation with input voltage from 150 V to 240 V or more.

The inverter unit Fubag IR 200 allows you to work with electrodes from 1.6 mm to 5 mm, allows you to cook at an input voltage of 150 V. Current adjustment - from 5 A to 200 A, ambient temperature - from -10 oC to +40 oC, has a hot start and ensures an even, stable short circuit arc.

The welding machine Svarog ARC 160 operates stably from 160 V to 245 V input power supply with stable arc ignition and rated current from 20 A to 160 A. It supports welding mode with a tungsten electrode in a protective environment, but has a low duty cycle of 40%.

The Interskol ISA 160 inverter also operates at a reduced network value, producing stable current readings from 20 A to 160 A. Duration of operation at a maximum PV current of 100%, there are functions of hot start, anti-stick and arc force. It is in demand due to its stability, ease of use and unpretentiousness.

The Aurora PRO Inter 200 inverter continues to operate even if it drops to 140 V, has multi-level protection and produces a welding current from 20 A to 200 A. It is possible to use 5 mm electrodes at maximum current, its duty cycle is 60%, and a characteristic feature is the ability to connect a network extension cord up to 100 m long with a wire cross-section of at least 2.5 mm2.

All these devices have a protection class of IP 21, weigh no more than 8 kg and have relatively low power consumption. Of course, if the network voltage is below 180 V, you cannot count on welding with a 5 mm electrode, but with a 3 mm electrode you can work at 150 V.

Results

We examined the operation of welding inverters at low voltage in the electrical network. You can choose an expensive stabilizer, or you can choose a welding machine with optimal characteristics, the choice is yours, and it depends on the type of work and financial capabilities.

Source: https://electrod.biz/apparat/svarochnyiy-invertor-dlya-ponizhennogo-napryazheniya.html

Operating principle and design of the welding inverter

To choose the right equipment for welding work, you need to know the design and operating principle of the welding inverter. If you have a good understanding of such issues, you can not only effectively use, but also repair inverter devices yourself.

Inverter welding machines made in Italy

There are many models of inverters offered on the modern market, which allows professionals to select equipment in accordance with their needs and financial capabilities. If you want to save money, you can make an inverter welding machine with your own hands.

How does an inverter welding machine work?

The operating principle of an inverter device is in many ways similar to the operation of a switching power supply. In both the inverter and the switching power supply, energy is transformed in a similar way.

The process of converting electrical energy in an inverter-type welding machine can be described as follows.

Alternating current with a voltage of 220 Volts flowing in a regular electrical network is converted into direct current.
The resulting direct current is again converted into alternating current using a special electrical circuit block of the inverter, but with a very high frequency.
The voltage of high-frequency alternating current is reduced, which significantly increases its strength.
The generated electric current, which has a high frequency, significant strength and low voltage, is converted into direct current, on which welding is performed.

Operating principle of a welding inverter

The main type of welding machines that were used previously were transformer devices, which increased the welding current by reducing the voltage value. The most serious disadvantages of such equipment, which is still actively used today, are low efficiency (since a large amount of consumed electrical energy is spent on heating the iron), large dimensions and weight.

The invention of inverters, in which the strength of the welding current is regulated according to a completely different principle, has made it possible to significantly reduce the size of welding machines, as well as reduce their weight. Effective regulation of the welding current in such machines becomes possible due to its high frequency. The higher the frequency of the current that the inverter generates, the smaller the dimensions of the equipment can be.

One of the main tasks that any inverter solves is increasing the frequency of standard electrical current. This is possible due to the use of transistors that switch at a frequency of 60–80 Hz.

However, as is known, only direct current can be supplied to transistors, while in a conventional electrical network it is alternating and has a frequency of 50 Hz.

To convert alternating current into direct current, a rectifier assembled on the basis of a diode bridge is installed in inverter devices.

After the transistor block, in which high-frequency alternating current is generated, in welding inverters there is a transformer that lowers the voltage and, accordingly, increases the current. To regulate voltage and current at high frequencies, smaller transformers are required (at the same time, their power is not inferior to larger analogues).

Welding inverter without protective casing

Elements of the electrical circuit of inverter devices

The welding inverter device consists of the following basic elements:

rectifier for alternating current coming from a regular electrical network;
an inverter unit assembled on the basis of high-frequency transistors (such a unit is a generator of high-frequency pulses);
a transformer that lowers the high-frequency voltage and increases the high-frequency current;
high-frequency alternating current rectifier;
working shunt;
electronic unit responsible for controlling the inverter.

Whatever characteristics a particular model of inverter device has, the principle of its operation, based on the use of a high-frequency pulse converter, remains unchanged.

Example of an inverter circuit diagram (click to enlarge)

The rectifier and inverter units of the equipment become very hot during their operation, so they are installed on radiators that actively remove heat. In addition, to protect the rectifier unit from overheating, a special temperature sensor is used, which turns off its power supply when it reaches a temperature of 90 degrees.

The inverter unit, which is essentially a generator of high-frequency high-power pulses, is assembled on the basis of transistors connected like an “oblique bridge”. High-frequency electrical pulses generated in such a generator are sent to a transformer, which is necessary to lower their voltage.

The most common transformers used to equip welding inverters are devices with the following characteristics: primary winding - 100 turns of PEV grade wire (0.3 mm thick); 1st secondary winding – 15 turns of copper wire with a diameter of 1 mm; 2nd and 3rd secondary windings - 20 turns of copper wire with a diameter of 0.35 mm. All windings are carefully insulated from each other, and their exit points are protected and sealed.

Internal structure of the welding inverter

The output rectifier of the welding inverter receives a high frequency current. Simple diodes cannot cope with converting such current into direct current. That is why the rectifier is based on powerful diodes with high opening and closing speeds. To prevent overheating of the diode block, it is placed on a special radiator.

A mandatory element of any welding inverter is a high-power resistor, which provides the device with a soft start.

The need to use such a resistor is explained by the fact that when the power is turned on, a powerful electrical impulse is supplied to the equipment, which can cause failure of the diodes of the rectifier unit.

To prevent this from happening, current is supplied through a resistor to the electrolytic capacitors, which begin to charge. When the capacitors reach full charge and the device enters normal operating mode, the contacts of the electromagnetic relay close and the current begins to flow to the rectifier diodes, already bypassing the resistor.

Output chokes on the welding inverter board

Thanks to their technical characteristics, inverters allow you to adjust the welding current in a wide range - from 30 to 200 A.

The operation of all elements of such a welding machine, characterized by compact dimensions, low weight and high power, is controlled by a special PWM controller.

Electrical signals are supplied to the controller from an operational amplifier, which is powered by the output current of the inverter itself.

Based on the characteristics of these signals, the controller generates corrective output signals that can be supplied to the rectifier diodes and transistors of the inverter unit - a generator of high-frequency electrical pulses.

In addition to the basic ones, modern welding inverters also have a whole list of useful additional options. Such characteristics, which greatly facilitate the work with the device and make it possible to obtain high-quality, reliable and beautiful welded joints, include forcing the welding arc (fast ignition), anti-sticking of the electrode, smooth adjustment of the welding current, and the presence of a protection system against overloads.

Circuit board with the main elements of the inverter

The feasibility of using inverters and their main disadvantages

The widespread use of welding inverters is explained by a number of significant advantages that they possess.

Devices of this type are characterized by high power and performance.
The weld seam formed using inverters is characterized by high quality and reliability.
Along with high power, devices of this type are compact in size and light in weight, which makes them easy to transport to the place where welding work will be performed.
Welding inverters have a high efficiency (about 90%), the consumed electrical energy is used in them more efficiently than in transformers.
Due to their high efficiency, such devices are characterized by economical consumption of consumed electricity.
In the process of welding work using an inverter, the molten metal splashes slightly, which is reflected in a more rational consumption of consumables.
Inverters provide the ability to smoothly adjust the welding current.
Due to the presence of additional options in such devices, the skill level of the welder has almost no effect on the quality of the work.
The wide versatility of inverters eliminates the question of which machine to choose for welding using various technologies.

Inverter devices are chosen when you need a device whose characteristics ensure high stability of the welding arc in any situation. When using inverters, the question does not arise about which electrode to choose for welding work, since with the help of this equipment you can weld metal with electrodes of any type.

Of course, inverters also have disadvantages, but there are not many of them. This should include the rather high cost of such devices compared to conventional welding transformers. Such devices are also expensive to repair, which is most often associated with the need to replace powerful transistors (their cost can be up to 60% of the price of the entire device).

Inverters are very sensitive to negative external factors - dust, dirt, precipitation and frost. If you need an inverter for work in the field, you will have to build a closed and heated area for it.

Source: http://met-all.org/oborudovanie/svarochnye/printsip-raboty-ustrojstvo-svarochnogo-invertora.html

Adjusting the current in a semi-automatic welding machine - Metals, equipment, instructions

One type of joining and cutting metals is electric welding. It is performed using welding machines and electrodes or special wire. The required current strength depends on the diameter of the electrode, the type of work - welding or cutting and the thickness of the metal. Therefore it needs to be regulated.

Despite the proliferation of new inverter devices, many people still have old devices in their garages and sheds that require manual adjustment. It cannot be done in the same way as adjusting the transformer current in a semi-automatic welding machine or inverter, in which this work is performed by electronics.

Design and principle of operation of a welding transformer

A transformer for electric welding, like any other, consists of three main elements:

Primary winding. Voltage is applied to it. In home devices, the coil is connected to a 220V network; in production, to reduce current consumption, 380V is supplied to it.
Secondary winding with voltage 45-110V. An electrode and ground are connected to it, and in welding rectifiers, diodes or a diode bridge.
Magnetic core. This is the core on which the coils are wound. It consists of a large number of transformer iron plates and can be toroidal, rectangular and W-shaped.

High-power devices are additionally equipped with starting and protective equipment, as well as fans.

There are three modes of operation of transformers:

Idle mode. In it, the device operates during a break during the welding process.
Work mode. This is welding or cutting metal.
Short circuit mode. Appears when the electrode is stuck.

The welding transformer current is adjusted in operating mode.

The main disadvantage of such a device is the variable output voltage. This makes it possible to use only carbon electrodes and weld only ordinary metal. Welding stainless and high-alloy steels requires special electrodes and the use of a welding rectifier.

Information! Unlike conventional transformers, welding machines have an operating mode similar to short circuit mode. Therefore, to reduce heating, they are wound with a wire of larger cross-section.

Welding rectifier

Using constant tension produces a better quality seam. It allows, in addition to conventional types of processing, to perform argon-arc welding and other types of work.

Information! In addition to single-phase devices, such devices are made into three-phase ones. This increases power with load distribution across three phases and provides a smoother, ripple-free output voltage.

THIS IS INTERESTING: How to use a welding machine

Welding rectifiers are distinguished by the type of installed rectifier units:

With two diodes. Instead of one secondary winding, two are wound and the diodes are connected according to a circuit with a common midpoint.
With a conventional diode bridge. In single-phase devices, a conventional bridge is installed, consisting of four diodes; in three-phase devices, a Larionov bridge is installed, consisting of six.
Transistor. Rarely found due to too powerful output transistors.
Thyristor. A type of diode devices, but instead of diodes, thyristors and a control system are installed. The adjustment is carried out by changing the opening angle of the thyristor and the effective voltage value.
Inverter. Modern electronic devices for individual use. The current is adjusted using control knobs or buttons located on the front panel.

These transformers are manufactured in different capacities and are designed to connect different numbers of posts:

Single-post. Can only be used by one welder. Adjustment is carried out both at the workplace and inside the device. The current-voltage characteristic can be steeply falling (soft), flat falling (hard), and also switchable.
Multi-post. They have sufficient power to connect several (up to 9) posts. The characteristic is only rigid; the welding process can only be adjusted at the workplace using ballast resistors.

Semi-automatic welding

The semi-automatic machine consists of two main components:

Wire feed unit. It feeds the wire into the welding zone and is additionally equipped with a shielding gas supply device.
Arc power device. It is used as a welding rectifier or inverter.

Reference! The current of the semi-automatic device is regulated in the device feeding the arc.

Device parameters

The main parameters are output current and voltage, as well as dynamic characteristics.

Output current and voltage

The main parameter of the welding machine is the output current. The diameter of the electrodes and the thickness of the metal depend on it. In individual devices it reaches 200A. Since the output voltage is important only when the arc is ignited, in modern inverter devices, in order to reduce power consumption and rectifier dimensions, this parameter is reduced as much as possible, and arc ignition is provided by additional built-in devices.

The output voltage in single-station devices is 45-65V. In large machines designed for simultaneous operation of several welders, the output voltage can reach 110V.

Dynamic response

When the distance from the end of the electrode to the part changes, the length of the arc and its resistance change. Therefore, no less important is the dynamic or current-voltage characteristic - the dependence of the current on the arc length:

Steeply falling, or soft. As the current increases in a device with such a characteristic, the voltage drops, which limits its increase. This provides a more stable arc as the distance to the part changes.

In homemade devices of low power, the soft characteristic is ensured by the internal device - the primary and secondary windings are wound on different parts of the magnetic circuit. Due to the design features without additional resistance, they could work with electrodes of a specific diameter for each device.

In higher power devices, the dynamic response is softened by ballast resistances. These methods can be combined.

Sloping or rigid characteristic. With a hard characteristic, the voltage does not change, but the current changes accordingly when the arc length changes. Large multi-post devices or automatic devices that maintain a constant distance between the electrode and the workpiece have such parameters.

Adjusting the welding machine

There are different ways to control the current of a welding machine.

With moving windings and core

The stiffness of the characteristic depends on the magnetic coupling between the primary and secondary coils. To change it, it is necessary to change the distance between the primary and secondary windings or the size of the air gap in the magnetic core. To do this, the core or coil is mounted on a special nut, and the screw is equipped with a handle. When it rotates, the nut is screwed on and the moving part changes its position, which leads to a change in current.

This method is used in alternating voltage devices, as well as those additionally equipped with diode bridges.

Core magnetization with constant voltage

Another control method is to magnetize the core with a constant voltage. The magnetized core increases the resistance to the magnetic flux created by the primary winding. This reduces the arc current.

Interesting! The operation of a magnetic amplifier is based on a similar principle. This device was used in electric drive control systems before the advent of thyristor converters.

Ballast resistances

One of the most common and simplest adjustment methods is to use ballast resistance:

Active ballast. It consists of several wire or tape resistances that are switched if necessary to change the electric welding current. Can be used with all types of devices. In homemade low-power devices, instead of a set of resistances, a nichrome spiral or snake is used.
Inductive ballast. This is a choke, the inductance of which can be changed, if necessary, by changing the number of turns or the size of the air gap in the magnetic circuit. Installed in series with the secondary winding before the diode bridge.

Thyristor control

This adjustment is used in rectifiers in which some or all of the diodes are replaced by thyristors. When the opening angle changes, the effective voltage value and current of the device changes. The angle is controlled by variable resistors or more complex circuits.

The disadvantage of this scheme is the transformation of constant voltage into pulsating voltage, which deteriorates the quality of the seam.

Important! When the opening angle is more than 90°, the amplitude value drops, which worsens the arc ignition process.

Adjusting the primary winding

The adjustment of the welding transformer currents through the primary is carried out by a thyristor switch - two thyristors connected back-to-back in parallel using a variable resistor connecting the control terminals or a small transistor circuit.

Adjustment of the primary thyristor switch allows you to control alternating voltage devices.

All these adjustment methods are losing their significance along with old devices and the spread of new, inverter ones. They are more economical, lighter, and some stores offer to exchange your old reel welder for a new one. But while the old devices are in operation, knowledge of how the welding current in the transformer is regulated will allow you to perform welding work more efficiently.

Source: https://spb-metalloobrabotka.com/regulirovka-toka-v-svarochnom-poluavtomate/

Design and principle of operation of a welding inverter - Ice advice

Inverter welding machines made in Italy

Features of the inverter for welding

Welding inverters are increasingly occupying the niche of industrial welding equipment, replacing traditional transformer technology. There is no doubt that this trend is global.

Inverter equipment objectively copes with the tasks facing it more successfully.

Advantages of inverter technology

The superiority of welding inverters over classic transformer-type converters is visible both in technological and economic aspects.

https://www.youtube.com/watch?v=ZlOj3ebCsbw

If we briefly list the benefits gained by introducing an inverter, we get something like this:

higher efficiency, exceeding 90%, which predetermines the design of the welding inverter itself, characterized by the absence of magnetic losses in the steel core of the transformer, inherent in the “classics”;
ability to work under conditions of varying supply voltage levels over a wide range without reducing technological parameters;
the ability to very accurately set the welding current with a digital indication of its value and strictly maintain the level during the welding process;
radically reduced overall dimensions and weight of the structure;
a whole range of completely new features inherent only in inverter devices, here are just a few of them.

New features include the presence of specific functions, including hot start, anti sticking, arc force, and others, making the welding process accessible even to a beginner. It is possible to use electrodes designed for welding with both alternating and direct current.

Source: https://LEDsovet.ru/ystroistvo-i-princip-raboty-svarochnogo-invertora/

Practice welding deception. How not to make a mistake when choosing a device. Part 2

This feature of the device, in the conditions of domestic power grids, is certainly important. If the inverter cannot cope with a network drawdown of up to 190V, it is worthless. Working in a garage or in a country house, in places where networks cannot boast of stability, will simply be impossible. Even if your outlet has a stable 220V, then when using extension cords of 30, 50 or 100 meters, drawdowns still cannot be avoided.

Deception, as in the case of additional functions, is caused by manufacturers' fear of losing in the competition. If all equipment sellers promise that their inverters operate at 160 V at the outlet, why not say that our “Oak” cannot operate at 120 V without losing quality in the seam.

The simplest way to check the performance of an inverter at reduced voltage is to use a device called LATR.

Laboratory AutoTransformer allows you to set the required voltage parameters and see how the welding machine connected through the device will cope with welding. As you understand, this equipment is not found in every garage.

The Aurora laboratory has this device, and we will definitely conduct tests for operation at low voltage in the network. So stay tuned for more video updates on the Aurora Online Channel.

The other extreme is the promise of welding equipment sellers that at 100-110V in the supply network, the device will produce the same welding result as at the rated voltage. This is definitely not true. The welding current of the machine decreases in proportion to the network voltage. The only question is at what voltage in the socket the quality of the seam when working with a given electrode diameter will become unacceptable. For some devices this is 180 V, for others 160 V.

Let us repeat once again, working with a supply voltage of 220 V is a guarantee of ideal fusion of the edges of the metal being welded; a decrease in voltage is an emergency situation and one cannot expect high quality welding seams under such conditions.

Judging by the advertisement, welding at ultra-low voltage in the supply network is almost the main requirement for the device. Meanwhile, we would like to draw the attention of buyers that welding is a multi-component process. In addition to the actual fusion of the metal edges, a significant amount of preparatory work needs to be carried out. Cut the workpieces, clean the welding area, and finally illuminate the welder’s workplace. And if the voltage drops to 140-160V, neither the angle grinder nor even the lighting will work.

Welding current control limits

This characteristic allows you to understand how the welding machine will cope with work with different electrode diameters. The thinner the metal being welded, the lower the welding current should be, and, accordingly, the diameter of the selected electrode. Considering that the minimum diameter of electrodes on sale is 1.6 mm, the current for them should be in the region of 40-50A. To work with large thicknesses of workpieces, the current, on the contrary, must be high, for a 4mm electrode, 140-200A.

It is worth recalling that the welding current is selected depending on the diameter of the electrode. For approximate calculations, the formula is used:

Isv=k x del

The values of the coefficient k can be found in the table:

del	2	3	4	5	6
k	25-30	30-45	35-50	40-55	45-60

The welding current control ratio is calculated by dividing the maximum welding current by the minimum.

Ist. max/Ist. Min.

For the simplest household MMA devices, this ratio should be at least 2, for professional equipment and production equipment - from 3 to 8.

Deception in this case may come down to exaggerating the range of adjustments. If the device produces a current from 80 to 120A, it will be difficult to work with electrodes thinner than 2.5 and thicker than 4 mm.

Stability and stability of the welding process

An amateur who encounters welding for the first time thinks that since the electrode “sparks,” that means the machine is working. This is not true. If the device lights an arc, this does not mean at all that the process of fusion of the edges of the metal being welded is proceeding as needed.

Source: https://Evrotek.Spb.ru/info/stati/i_welding/49030/

The design and operating principle of welding machines, how to choose a welding machine

Welding is a method of connecting and separating metals by means of electric current and is based on the formation of an arc between the processing area - the first electrode, and the handle brought to the area - the second electrode, connected to the corresponding pole of the electric current. In this way, parts are connected, metals are separated or cut, drilling and making cavities and holes, and fusing in layers.

Arc welding is widely used, because thanks to this technology it has become possible to make a permanent connection of metal parts, and the strength of the seam is the same as that of a solid material. This circumstance is due to the continuity of the formed structures and molecular bonds between parts.

Electric arc

Temperatures of thousands of degrees Celsius are provided by an electric arc, which is essentially a short circuit between two electrodes located quite close to each other. The voltage applied to the electrodes increases until there is a breakdown of the air, which is an insulator.

Breakdown is the emission of electrons from the cathode. The electrons heated by the current come out and are directed to the ionized atoms of the anode. Then a discharge appears, the air in the gap is ionized, plasma is formed, the resistance of the air gap decreases, the current increases, the arc heats up, and becomes a conductor and closes the circuit. The process is called “ignition” of the arc. The arc is stabilized by establishing the required distance between the electrodes and maintaining the power supply characteristics.

Welding metals

The choice of a good electrode and welding method is extremely important, since it determines whether its mechanical properties will be similar to those of the base metal.

The weld pool must be protected from exposure to air to prevent metal oxidation. For this purpose, a special environment is created in the work area, which is achieved in two ways:

MIG-MAG technology, when argon, helium or CO2 is supplied from a special cylinder.
Burning of the electrode coating and the formation of a protective slag or slag-gas “dome”.

During the combustion process, the electrode coatings bind and remove oxygen from the seam. In addition, the substances contained in them help to ionize the arc, refine and alloy the weld metal.

In terms of stability of power supply, welding is a rather capricious process, because the required temperature regime is directly dependent on the current parameters. The stability of the electric arc must be ensured. Only a stable arc will prevent the appearance of seam defects, especially during ignition and extinction.

THIS IS INTERESTING: How electrode brands are deciphered

The more massive the parts being welded, the deeper the melting must be, the larger the diameter of the electrode, the more force and power is required for work. The operator can often determine the current strength only experimentally; sometimes it is adjusted during the welding process, and sometimes it is rigidly fixed. Arc burning from a direct current source is more stable, without interruptions.

When consuming direct current, there is no polarity, less metal spatter is generated, and the seam is of better quality. Welding with alternating current is somewhat more difficult, because in order to maintain the arc the worker must have serious skills; in this case, high-quality welding is difficult to achieve. It is recommended to weld aluminum and its alloys using alternating current.

Different types of welding machines have different technical features, their pros and cons.

Inverters: pros and cons

These are the youngest welding machines; their mass production was launched only in the 1980s. Rectifiers with transistor inverter. In these sources, electricity changes its characteristics many times. When current is passed through a semiconductor, it is rectified, and then a special filter smoothes it out. The constant standard network frequency of 50 Hz is converted into alternating again, but with a frequency of tens of kilohertz.

After frequency inversion, the current goes to a miniature transformer, where its voltage decreases and strength increases. Then the high-frequency filter and rectifier begin to do their work - direct current is supplied to the electrodes to form an arc.

Increasing the frequency of the current is the main achievement of the inverter. The advantages also include:

High efficiency (85-95%).
Possibility of power supply from a regular outlet.
Long period of continuous operation.
Wide range of current values.
Smooth adjustment of current and voltage.
The operating mode is controlled by microprocessors and control circuits.
Protection against voltage surges.
High quality weld.
Possibility of joining materials that are difficult to weld.
Increased electrical safety.

Disadvantages of inverters:

High price.
Poor reaction to dust entering the housing.
Electronics are sensitive to moisture and cold, which can lead to condensation.
The probability of interference occurring in the main network.

Welding transformers

Today these are the most common welding machines, relatively inexpensive and simple in design, reliable. Electricity conversion is carried out by a power transformer with a standard frequency of 50 Hz.

The current is adjusted by mechanically adjusting the magnetic flux in the composite core. The primary winding is powered from the network, the core is magnetized, and an alternating current of lower voltage (50-90 V) and higher strength (100-200 A) is induced on the secondary winding, it forms an arc.

The fewer turns on the secondary winding coils, the lower the voltage and the greater the current.

Advantages:

Low cost (two to three times cheaper than inverters).
Simplicity of design.
Maintainability.
Reliability.

Flaws:

Large weight and dimensions.
Due to alternating current, it is difficult to obtain a high-quality seam.
Difficulty holding the arc.
Relatively low efficiency (no more than 80%).
Inability to connect to the intra-house network.

Welding rectifiers

The mains current in these devices does not change frequency and is induced on the windings with a decrease in voltage. After conversion, it passes through another block of selenium or silicon rectifiers. The electrodes are supplied with direct current. Thanks to this, the electric arc is very stable, without significant interruptions and surges.

In most cases, fan cooling is required. Often devices have additional chokes to improve the characteristics of the outgoing current, which is smoothed and filtered. Complete with rectifiers there may be protective, measuring and control equipment. The stability of temperature and current is important here, so wind relays, thermostats, fuses, and circuit breakers are installed. The most common rectifiers are three-phase.

Advantages of welding rectifiers:

High quality seam.
Easy to maintain the arc.
Minimal splashing of additive material.
Great melting depth.
Smaller dimensions and weight compared to AC transformers.
Possibility of welding cast iron, non-ferrous metals, heat-resistant steel.

Flaws:

High price.
The need to carefully monitor the condition of the cooling system.
In most cases, there is no possibility of power supply from a household network.
The efficiency is less than that of an inverter.
Relatively complex design.

Semi-automatic devices: characteristics

Using a special mechanism, the welding wire is fed into the working area, where it is melted in the active gas and directed into the weld pool. The gas displaces the air near the weld pool and protects the seam from oxygen. Carbon dioxide, argon, helium, and combinations of these gases are used for this purpose. With the use of flux-cored wire, gas does not need to be supplied to the work area.

Pros:

Ease of welding thin sheet parts.
The quality of the seam, the possibility of obtaining a “short seam”.
Wide range of weldable materials.
High performance.
Wide range of settings and adjustments.

Minuses:

High price.
High cost of consumables.
It is necessary to use cylinders or connect to a special network.
It is difficult to work outdoors, where the gas environment must be protected from blowing away.

Mains voltage . It can be single or three phase. For non-industrial use, a 220 V device or a universal “220/380” machine is recommended. Most devices can fail or stop cooking due to voltage surges. In this regard, the inverters are equipped with protection against voltage surges. For household units, the range is 10-15% wider, while professional models require a voltage of 165-270 V.

Open circuit voltage . This characteristic determines the ability of the device to ignite an electric arc and maintain its combustion. In order for the arc to be excited, the voltage must be approximately 1.5-2.5 times the voltage of a stable burning electric arc.

Power . Datasheets often indicate the maximum power of the welding machine’s power source, corresponding to the maximum load on the network. If the units are kW, then we are talking about active power; if kVA, we are talking about apparent power, which is usually higher due to the correction factor.

Real power is determined by the current strength that the device is capable of delivering. This indicator determines the thickness of the metal being welded and the maximum diameter of the electrode.

Protection class . The passport must contain a 2-digit IP code. The index of average power sources for welding is IP21-IP23. The deuce says that objects thicker than 12 mm will not penetrate inside the case. The second number indicates protection from moisture - 1 - means that drops of water falling vertically onto the casing will not cause harm; 3 means that even at an angle of 60°, water will not penetrate into the body of the device. But cooking in the rain is prohibited!

Temperature range . According to GOST, manual welding can be carried out at temperatures of -40–40 ° C. However, not all welding machines can be put into operation at temperatures below zero degrees. Most often, problems appear with inverters, in which, at sub-zero temperatures, the overload indicator simply lights up and the welding machine turns off.

Powered by a generator . This feature is useful for working in the field. Not all devices can be powered by household generators with internal combustion engines.

Many power sources make it easier to hold the arc: “Anti-stick on switch-off”, “Hot start”, “Arc force”, “Ignition on rise”. It is useful to pay attention to the indication of parameters, functionality, breadth of operating adjustments, overload protection, quality of markings, electrical safety, completeness, ergonomics, and maintainability. It is recommended to purchase a device with maximum technical characteristics in the passport, and it is recommended to buy the passport in Russian.

Source: https://tokar.guru/svarka/tipy-svarochnyh-apparatov-princip-raboty-ustroystva.html

Real characteristics of Resanta welding inverters

Resanta welding inverters are very popular among welders today, and that is why it is impossible not to pay attention to this brand in more detail. The devices are sold at a fairly reasonable and affordable price, but the quality remains acceptable if you add up all the pros and cons.

This is not an advertisement for Resanta, especially since Internet users, especially welders, have already formed a “negative conditioned reflex” to intrusive and biased advertising materials focused on sales, and not on the search for truth. To get closer to the latter, we will test the Resanta line of K series devices; we present to your attention a report on the work done.

You can draw your own conclusions about the compliance of the real characteristics of Resant with the declared ones.

The series includes 4 SAI 160K devices; SAI 190K; SAI 220K; SAI 250K. The letter "K" in this case means "compact". You can always find out the current cost of these devices on the official website, so we won’t give any numbers here.

Let's start with researching the configuration

All devices are supplied in cardboard boxes with the same equipment: operating instructions, carrying strap, welding cables. The length of the holder cables for all devices is 190 cm; ground cable – 120 cm. The cable packages are not marked, but differ noticeably in cross-section:

The 160K inverter comes with very thin cables with a cross-section of 10-12 square meters. mm;
The 190K and 220K inverter is equipped with a 14 kV cable. mm;
250K has the largest cross-section - about 16 square meters. mm.

It should be noted that copper-plated aluminum welding cables have insufficient cross-sections and will heat up during operation.

It is also worth noting that the bayonet connectors of 220 and 250A inverters must be of a larger cross-section, otherwise contact burnout cannot be avoided during serious use.

As for the power cable, the one and a half meter wire has an insufficient cross-section of 1.5 sq mm on models 160K and 190K. The 220K device has a strange cable with a cross section of 3x1.8 square meters. mm. There are no questions about the power cable to the 250A device; its cross-section is 2.5 square meters. mm.

Features of the device design

Among the advantages of the “K” line, one should note neat machine assembly, a sufficient level of maintainability, and the use of the new generation of IGBT transistors GT50JR22 from Toshiba. The new elements are characterized by increased speed and low saturation voltage compared to traditional FGH40N60.

New transistors make it possible to increase the clock frequency of the inverter and reduce the size of reactive elements: input capacitors, pulse transformer, etc. However, in pursuit of small dimensions, the developers worsened the cooling conditions.

The radiators have become smaller compared to the full-size version of the devices, but the fan power has not changed. In order to prevent the compact source from eternal overheating, engineers had to reduce the maximum welding currents using a PWM controller.

That is 160A; 190A; 220A; 250A inverters will be able to produce only 120A; 130A; 170A; 180A.

To find out what the sources are, we connect them to the AWR-224MD welding process recorder, load them with current using ballast rheostats and take the current-voltage characteristics.

Let's start with the open circuit voltage

Model Resanta	Stated Uхх, В	Actually Uхх, В
SAI 160K	85	82
SAI 190K	80	65
SAI 220K	80	82
SAI 250K	80	82

We can say that the XX voltage of the three devices corresponds to that declared by the manufacturer. Resanta 190K produces Uхх below the declared value, but still within acceptable limits.

Welding currents and shape of the current-voltage characteristic

Let's consider the current-voltage characteristics of the devices and draw conclusions about their operating properties.

Characteristics	SAI 160K	SAI 190K	SAI 220K	SAI 250K
Maximum welding current, A	120 (application 160)	138 (application 190)	162 (application 220)	183 (application 250)
Short circuit current at max. current, A	160	164	235	233

To summarize, we can say that none of the test participants passed the test. You can calculate for yourself how many amperes of rated current each inverter does not deliver. That is, the price of welding power supplies includes clean Chinese air, which amounts to 25 to 35% of the price of the devices. As for the shape of the current-voltage characteristic, it can be assumed that the ignition process and the stability of the arc must be at an acceptable level.

Checking PN

Since the current characteristics of all inverters are overestimated, the voltage limit indicated on the inverter nameplates is also not true.

To imagine what load duration the sources have, let’s calculate their approximate operating mode. To do this, all devices will be loaded with their real maximum current and placed in a heat chamber (at a temperature of 40 degrees).

Based on the time that each source can stay in the thermal circuit without turning off, we will draw conclusions about the real PN.

When coming to the store to buy a new welding inverter, a professional welder pays attention to the continuous load current, which is indicated on the nameplate. The numbers indicated there indicate the threshold current values that the welder can set at the source without fear of the machine shutting down due to overheating, regardless of operating time. Incorrect data indicated in the PN100% column can mislead the welder and lead to forced downtime.

Test results obtained in a thermal chamber

Inverter	Imax, A (maximum inverter current in the thermal chamber)	Time spent in the chamber before the overheating indicator turns on	Real value PN, % at max. current	Declared PN value, % at max. current	Real PN 100% (continuous load current), A	Declared PN100%, (Continuous load current), A
SAI160K	120	2 min 36 sec	26	70	61	100
SAI 190K	140	2 min 14 sec	22	70	65	120
SAI 220K	160	1 min 56 sec	19	70	70	140
SAI 250K	183	3 min 13 sec	32	70	101	160

Low voltage operation

All devices of the “K” series can withstand drawdown up to 160V, except for the SAI160K model (when welding with rutile electrodes, approx. 46.00). Ignition at SAI 160K becomes unsatisfactory, and the welding arc often breaks.

Add. Functional

The instructions say that all SwarApps are equipped with the “anti-stick”, “hot start” and “arc force” functions.

Actual availability

Model	anti-sticking	Hot start	Fast and Furious Arcs	VRD
K series inverters	Yes	No	No	No

Practical welding

All devices cope well with welding steel plates (butt-welding) 4 mm thick with OK46.00, UONII 13/55 electrodes with a diameter of 2.5 mm. Ignition is confident, the arc is stable and elastic. As for electrodes with a diameter of 4 mm, on models 160K and 190K there is a noticeable lack of current, the regulators have to be set to maximum values, the other two inverters cope with welding with a 4mm electrode normally (the process is quite comfortable).

Conclusion

Most of the characteristics of the Resanta “K” series devices do not correspond to the declared ones. The discrepancy between the promised and actual functionality concerns both the maximum welding currents and PN of the inverter, and the lack of additional functions of arc force and hot start.

Source: http://svarka-master.ru/real-ny-e-harakteristiki-svarochny-h-invertorov-resanta/