AC(English alternating current) - alternating current.
DC(English direct current) - D.C..
MMA(Eng. Manual Metal Arc) - manual arc welding with stick electrodes. We know it under the name RDS.
TIG(Eng. Tungsten Inert Gas) - manual welding tungsten non-consumable electrodes in a protective gas environment (argon).
MIG/MAG(Eng. Metal Inert / Active Gas) - semi-automatic arc welding with a consumable electrode wire in an inert (MIG) or active (MAG) gas environment with automatic wire feed.
PV(PR, PN, PVR) - on duration - the time that the device is able to operate at a certain current (the current is indicated together with PV) before automatic shutdown due to overheating. The PV value is indicated as a percentage relative to the standard cycle, which is taken equal to 10 or 5 minutes. If the duty cycle is 50%, this means that with a cycle of 10 minutes, after 5 minutes of continuous operation, 5 minutes of inactivity is required for the machine to cool down. This parameter can be equal to 10%, so you need to pay attention to it. The concepts: duration of operation (PV), duration of work (PR), duration of load (PN) have different meanings, but the essence is the same - the continuity of welding.
An easy-to-understand diagram of a welding transformer is as follows:
A simple diagram of a welding transformer: 1 - transformer; 2 - reactor with variable inductance; 3 - electrode; 4 - welded part.
To limit the short-circuit current and stable arcing, the transformer must have a steeply falling external current-voltage characteristic ( . To do this, they either use transformers with increased scattering, as a result of which the short-circuit resistance is several times greater than that of conventional power transformers. Or, a reactive coil with a large inductive resistance is included in the circuit with a transformer with normal scattering - a choke (the choke can be included not in the secondary winding circuit, but in the primary circuit, where the current is less). If the inductance can be changed at the inductor, adjusting it, they change the shape of the external current-voltage characteristic of the transformer and the arc current I 21 or I 22 corresponding to the arc voltage Ud.
Welding current control. The current strength in welding transformers can be regulated by changing the inductive resistance of the circuit (amplitude regulation with normal or increased magnetic scattering) or by means of thyristors (phase regulation).
In amplitude control transformers, the required welding current parameters are provided by moving moving coils, magnetic shunts or using a separate reactive coil as in the figure above. In this case, the sinusoidal form of the alternating current does not change.
Scheme of a welding transformer with movable windings: 1 - primary winding, 2 - secondary, 3 - rod magnetic circuit, 4 - screw drive.
Scheme of a welding transformer with a movable magnetic shunt: 1 - primary winding, 2 - secondary, 3 - rod magnetic circuit, 4 - movable magnetic shunt, 5 - screw drive.
There may be a simple change in the number of turns used in the transformer winding, to reduce the open circuit voltage and hence the welding current.
Transformers with thyristor (phase) regulation consist of a power transformer and a thyristor phase regulator with two anti-parallel thyristors and a control system. The principle of phase regulation consists in converting a sinusoidal current form into alternating pulses, the amplitude and duration of which are determined by the angle (phase) of the thyristors.
Scheme of a welding transformer with thyristor control. BZ - task block, BFU - phase control block.
The use of a thyristor phase regulator makes it possible to obtain welding machine, the characteristics of which compare favorably with the characteristics of a transformer with amplitude regulation. In more complex schemes control than in the figure above, a square-wave alternating current is generated. And in this case, for example, an increased rate of transition of the pulse through the zero value is achieved, as a result of which the time of current-free pauses is reduced and the stability of the arc burning and the quality of the weld are increased. What can not be said about the oscillogram shown above, on it the current-free gaps are larger than those of transformers with amplitude regulation and the quality of welding is worse.
Another advantage of thyristor devices is the simplicity and reliability of the power transformer. The absence of steel shunts, moving parts and associated increased vibrations makes the transformer easy to manufacture and durable in operation.
According to the type of supply network, welding transformers are single-phase and three-phase. The latter, as a rule, can be connected to single-phase network. The figure below shows a single-phase and three-phase transformers with current regulation by a magnetic shunt.
Advantages and disadvantages of welding transformers. The advantages of welding transformers include a relatively high efficiency (70-90%), ease of operation and repair, reliability and low cost.
The list of disadvantages is longer. First of all, this is the low stability of the arc, due to the properties of the alternating current itself (the presence of current-free pauses when the electric signal passes through zero). For high-quality welding, it is necessary to use special electrodes designed to work with alternating current. Negatively affect the stability of the arc and fluctuations in the input voltage.
The welding transformer cannot weld stainless steel, which requires direct current, and non-ferrous metals.
If the power of the AC welding machine is large enough, its weight may cause certain difficulties when moving the transformer from place to place.
And yet, an inexpensive, reliable and unpretentious welding transformer is not such a bad choice for a home. Especially if you rarely have to cook, and there is not enough money to buy a more functional model.
Welding rectifiers
Welding rectifiers are devices that convert the alternating mains voltage into constant pressure electric welding. There are many schemes for constructing welding rectifiers with various mechanisms for generating the output parameters of current and voltage. Are used various ways current regulation and formation of an external current-voltage characteristic of rectifiers ( read about the current-voltage characteristic at the end of the article): changing the parameters of the transformer itself (moving coils and sectioned windings, magnetic shunts), using a choke, phase regulation using thyristors and transistors. In the simplest devices, the current is regulated by a transformer, and diodes are used to rectify it. The power part of such devices consists of a transformer, a rectifier unit on uncontrolled valves and a smoothing choke.Block diagram of the welding rectifier: T - transformer, VD - rectifier unit on uncontrolled valves, L - smoothing choke.
The transformer in such a circuit is used to lower the voltage, form the necessary external characteristic and control the mode. More modern and advanced devices include thyristor rectifiers, in which mode control is provided by a thyristor rectifier unit, which performs phase control of the thyristor turn-on moment. The formation of the necessary external characteristics is carried out by introducing feedback on the welding current and output voltage.
Block diagram of the welding rectifier: T - transformer, VS - thyristor rectifier unit, L - smoothing choke.
Sometimes a thyristor regulator is installed in the primary winding circuit of the transformer, then the rectifier unit can be assembled from uncontrolled valves - diodes.
Block diagram of the welding rectifier: VS - thyristor rectifier unit, T - transformer, VD - rectifier unit on uncontrolled valves, L - smoothing choke.
Semiconductor elements of rectifiers need forced cooling. To do this, they put radiators blown by a fan.
The figure below shows a diagram of a welding rectifier in which a change in the resistance of the transformer and current regulation is provided using a magnetic shunt - by closing or opening it using the knob on the front panel of the device.
Schematic diagram of a welding rectifier with a magnetic shunt: A - circuit breaker, T - transformer, Dr - magnetic shunt, L - light-signal fittings, M - electric fan, VD - diode rectifier unit, RS - shunt, PA - ammeter.
Single-phase AC rectification circuits are used in circuits with low power consumption. Compared to single-phase circuits, three-phase circuits provide significantly less rectified voltage ripple. The operation of a three-phase Larionov bridge rectification circuit using diodes, used in many welding rectifiers, is shown in the figure below.
Advantages and disadvantages of welding rectifiers. The main advantage of rectifiers, in comparison with transformers, is the use of direct current for welding, which ensures ignition reliability and stability of the welding arc and, as a result, a better weld. It is possible to cook not only carbon and low-alloy, but also stainless steel and non-ferrous metals. It is also important that welding with a rectifier produces less spatter. In essence, these advantages are quite enough for an unambiguous answer to the question of which welding machine to choose - a transformer or a rectifier. If, of course, do not take into account prices.
The disadvantages include the relatively large weight of the devices, the loss of part of the power, a strong "drawdown" of the voltage in the network during welding. The latter also applies to welding transformers.
Welding inverters
The word "inverter" in its original meaning means a device for converting direct current into alternating current. The figure below shows a simplified diagram of an inverter-type welding machine.
Block diagram of the welding inverter: 1 - mains rectifier, 2 - mains filter, 3 - frequency converter (inverter), 4 - transformer, 5 - high-frequency rectifier, 6 - control unit.
The operation of the welding inverter is as follows. Alternating current with a frequency of 50 Hz is supplied to the mains rectifier 1. The rectified current is smoothed by filter 2 and converted (inverted) by module 3 into alternating current with a frequency of several tens of kHz. Frequencies of 100 kHz are currently being achieved. It is this stage that is the most important in the operation of the welding inverter, which allows to achieve huge advantages over other types of welding machines. Further, with the help of transformer 4, the high-frequency alternating voltage is reduced to idle values (50-60V), and the currents are increased to the values necessary for welding (100-200A). The high-frequency rectifier 5 rectifies the alternating current, which does its useful work in the welding arc. Influencing the parameters of the frequency converter, they regulate the mode and form the external characteristics of the source.
The processes of current transition from one state to another are controlled by the control unit 6. In modern devices, this work is performed by IGBT transistor modules, which are the most expensive elements of the welding inverter.
The feedback control system generates ideal output characteristics for any method of electric welding ( read about the current-voltage characteristic at the end of the article). Due to the high frequency, the weight and dimensions of the transformer are reduced significantly.
According to their functionality, inverters of the following types are produced:
- for manual arc welding(MMA);
- for argon-arc welding with non-consumable electrode (TIG);
- for semi-automatic welding in shielding gases (MIG/MAG);
- universal devices for operation in MMA and TIG modes;
- semiautomatic devices for work in MMA and MIG/MAG modes;
- devices for air-plasma cutting.
As you can see, a significant part of the volume is occupied by radiators of the cooling system.
Advantages of inverters. The advantages of welding inverters are great and numerous. First of all, their low weight (4-10 kg) and small size, allowing you to easily move the machine from one welding site to another. This advantage is due to the smaller size of the transformer due to the high frequency of the voltage it converts.
The exclusion of the power transformer from the circuit also made it possible to get rid of losses for heating the windings and remagnetization of the iron core and achieve high efficiency (85-95%) and an ideal power factor (0.99). When welding with an electrode with a diameter of 3 mm, the power consumed from the network for an inverter-type welding machine does not exceed 4 kW, and for a welding transformer or rectifier, this figure is 6-7 kW.
The inverter is capable of reproducing almost all kinds of external current-voltage characteristics. This means that it can be used to perform all major types of welding - MMA, TIG, MIG/MAG. The device provides welding of the alloyed and stainless steels and non-ferrous metals (in the MIG/MAG mode).
The device does not require frequent and prolonged cooling during intensive work, as required by other household types of welding machines. Its PV reaches 80%.
The inverter has a smooth adjustment of welding modes in a wide range of currents and voltages. It has a much wider range of welding current adjustment than conventional devices - from several amperes to hundreds and even thousands. For domestic use, low currents are especially important, which allow welding with thin (1.6-2 mm) electrodes. Inverters provide high-quality formation of the seam in any spatial position and minimal spatter during welding.
Microprocessor control of the device provides stable current and voltage feedback. This allows you to provide the most useful and convenient functions of Arc Force, Anti Stick and Hot Start. The essence of all of them is a qualitatively new control of the welding current, which makes welding as comfortable as possible for the welder.
- The Hot Start function provides an automatic increase in current at the start of welding, making it easier to strike the arc.
- The Anti Stick function (anti-sticking) is a kind of antipode of the Hot Start function. When the electrode comes into contact with the metal and there is a threat of its sticking, the welding current is automatically reduced to those values that do not cause the electrode to melt and weld to the metal.
- The Arc Force function (arc forcing) is realized when a large drop of metal separates from the electrode, reducing the length of the arc and threatening to stick. An automatic increase in the welding current for a very short time prevents this.
These convenient features allow low-skilled welders to successfully cope with the welding of the most complex metal structures. For those who have ever worked with a welding inverter, the question - which welding machine is better - does not exist. After a transformer or rectifier, working with an inverter turns into a pleasure. It is no longer necessary to "hollow" the electrode in order to ignite an arc that does not want to ignite, or frantically tear it off if it is tightly welded. You can simply put the electrode on the metal and, tearing it off, calmly ignite the arc - without worrying that the electrode can be welded.
Inverter welding machines can be used with large drops in mains voltage. Most of them provide welding in the mains voltage range of 160-250V.
Disadvantages of welding inverters. It is difficult to talk about the shortcomings of such a perfect device as welding inverter and yet they are. First of all, this is the relatively high price of the device and the high cost of its repair. If the IGBT module fails, you will have to pay an amount equal to 1/3 - 1/2 of the cost of a new device.
The inverter imposes increased requirements, in comparison with other welding machines, to the conditions of storage and operation, due to its electronic filling. The device does not respond well to dust, since it worsens the cooling conditions for transistors, which get very hot during operation. They are cooled with aluminum radiators, the deposition of dust on which impairs heat transfer.
Dislikes electronics and low temperatures. Any minus temperature is undesirable due to the appearance of condensate on the boards, and minus 15°C can become critical. Storage and operation of the inverter in unheated garages and workshops in winter are undesirable.
Welding semi-automatic
Speaking of welding equipment, one cannot ignore semi-automatic devices - devices for welding in a shielding gas environment with a mechanized feed of the welding wire.
Semi-automatic welding comprises:
- current source;
- control unit;
- welding wire feed mechanism;
- a pistol (torch) with a sleeve-electric wire, through which the supply of protective gas, wire and electric signal is carried out;
- gas supply system, consisting of a gas cylinder, an electromagnetic gas valve, gas reducer and hose.
Welding rectifiers or inverters are used as a current source. The use of the latter improves the quality of welding and increases the amount of welded materials.
According to the design, semi-automatic welding machines are double-case and single-case. In the latter, the power source, control unit and wire feeder are housed in one housing. For double-case models, the wire feed mechanism is placed in a separate unit. Usually these are professional models that support long-term operation at high current. Sometimes they are equipped with a pistol water cooling system.
Semi-automatic welding in MMA mode is no different from working with a conventional welding machine. When using the MIG/MAG mode, an electric arc burns between a continuously supplied consumable welding wire and material. Carbon dioxide (or its mixture with argon) supplied through the gun protects the welding zone from the harmful effects of oxygen and nitrogen contained in the air. Using semi-automatic welding machines, high-alloy and stainless steels, aluminum, copper, brass, and titanium are welded.
Semi-automatic welding is one of the most modern technologies arc welding, ideal not only for production, but also for the home. Semiautomatic devices are widely used in industry and everyday life. There is information that at present in Russia up to 70% of all welding work produced by semi-automatic welding. This is facilitated by the wide functionality of the equipment, high quality welding and ease of operation. Semi-automatic welding machine is very convenient for welding thin metal in particular car bodies. Not a single car service enterprise can do without this most convenient equipment.
Choosing a welding machine
The choice of welding machine should be made according to specific needs. Before you go to the store, you need to know the answers to the following questions.- What metal - by brand and thickness - is to be welded?
- Under what conditions will the work be carried out?
- To what extent?
- What are the requirements for the quality of work and qualifications of the welder?
- And, finally, how much can be spent on the purchase of a welding machine?
Depending on the answers to these questions, the requirements for the purchased equipment should be formed.
If you have to weld not only carbon and low alloy steel, but also high alloy and stainless steel, then the choice must be made between a welding rectifier and an inverter. If you have to weld metals that require protection from oxygen or nitrogen in the air, such as aluminum, then you will need welding in a shielding gas environment, which can be provided by a semiautomatic device with MIG / MAG mode.
In general, if we talk about the versatility of equipment, then the best choice, perhaps, there will be a semi-automatic with MMA and MIG / MAG modes. Its presence will allow you to perform almost any work on welding metals, which you only have to deal with in everyday life.
If you have to deal with thin (thinner than 1.5 mm) metal, preference should again be given to a semiautomatic device.
Work at sub-zero temperature, especially at values below 10-15 °C, is undesirable for inverters. Strong dustiness also affects them badly. The conclusion is this. If you have to work at very low temperatures in conditions of high dust content, there may be no other option but to choose a welding machine without state-of-the-art electronics - a welding transformer, a diode rectifier or a semi-automatic device based on the latter.
High requirements for the quality of welding and low qualification of the welder definitely incline to the choice of a welding inverter with its ease of use and Arc Force, Anti Stick, Hot Start functions.
A large amount of work requires a high duty cycle (duty cycle) from the welding machine, otherwise too much time will be spent on downtime during its cooling. PV is one of the characteristics that distinguish household welding machines from professional ones. For the latter, it is quite large or even reaches 100%, which means that the device can work without interruption for as long as you like. If we talk about household models, then the PV of inverters is significantly superior to the PV of welding transformers and rectifiers. It is better to take 30% as the minimum value of PV.
When choosing a welding machine, you need to think about the neighbors. If you have to cook a lot, and the mains voltage is low and unstable, you should choose a welding machine for your home, taking into account the power it consumes. The constant flashing of light bulbs, which occurs during the operation of powerful welding transformers and rectifiers, excites universal hatred for welder neighbors. The inverter with its energy saving and anti-stick function will not harm good neighborly relations. When the electrode comes into contact with the metal to be welded, the welding transformer drains the mains, while the inverter simply reduces the welding current (terminal voltage), plus the inverter is more efficient at low mains voltage.
Basic requirements for power sources for welding
To meet their intended purpose, current sources must meet certain requirements, the main of which include the following:- the open circuit voltage must ensure the ignition of the arc, but not be higher than values that are safe for the welder;
- power sources must have devices that regulate the welding current within the required limits;
- welding machines must have a specified external current-voltage characteristic consistent with the static current-voltage characteristic of the welding arc.
An arc can occur either in the event of a gas (air) breakdown, or as a result of the contact of the electrodes with their subsequent withdrawal to a distance of several millimeters. The first method (air breakdown) is possible only at high voltages, for example, at a voltage of 1000 V and a gap between the electrodes of 1 mm. This method of starting an arc is usually not used due to the danger of high voltage. When the arc is powered by high voltage current (more than 3000V) and high frequency (150-250 kHz), air breakdown can be obtained with a gap between the electrode and the workpiece up to 10 mm. This method of ignition of the arc is less dangerous for the welder and is often used.
The second method of ignition of the arc requires a potential difference between the electrode and the product of 40-60V, therefore it is used most often. When the electrode comes into contact with the workpiece, a closed welding circuit is created. At the moment when the electrode is removed from the product, the electrons that are on the cathode spot heated from a short circuit break away from the atoms and move towards the anode by electrostatic attraction, forming an electric arc. The arc quickly stabilizes (within a microsecond). The electrons that come out of the cathode spot ionize the gas gap and a current appears in it.
The arc ignition speed depends on the characteristics of the power source, on the current strength at the moment the electrode contacts the workpiece, on the time of their contact, and on the composition of the gas gap. The arc excitation speed is affected, first of all, by the magnitude of the welding current. The greater the current value (with the same electrode diameter), the greater the cross section of the cathode spot becomes and the greater the current will be at the beginning of the arc ignition. A large electron current will cause rapid ionization and transition to a stable arc discharge.
With a decrease in the diameter of the electrode (ie, with an increase in current density), the transition time to a stable arc discharge is further reduced.
The arc ignition speed is also affected by the polarity and type of current. With direct current and reverse polarity (i.e., the plus of the current source is connected to the electrode), the arc excitation speed is higher than with alternating current. For alternating current, the ignition voltage must be at least 50-55V, for direct current - at least 30-35V. For transformers that are designed for a welding current of 2000A, the open circuit voltage should not exceed 80V.
Re-ignition of the welding arc after its extinction due to short circuits by drops of electrode metal will occur spontaneously if the temperature of the electrode end is high enough.
The external current-voltage characteristic of the source is the dependence of the voltage at the terminals and the current.
In the diagram, the source has a constant electromotive force (Ei) and internal resistance (Zi), consisting of active (Ri) and inductive (Xi) components. At the external terminals of the source we have voltage (Ui). In the "source-arc" circuit, there is a welding current (Id), which is the same for the arc and the source. The source load is an arc with active resistance (Rd), the voltage drop across it is Ud=I Rd.
The equation for the voltage at the external terminals of the source is the following: Ui = Ei - Id Zi.
The source can operate in one of three modes: idle, load, short circuit. When idling, the arc does not burn, there is no current (Id = 0). In this case, the source voltage, called the open circuit voltage, has a maximum value: Ui = Ei.
With a load, a current (Id) flows through the arc and the source, and the voltage (Ui) is lower than at idle by the amount of voltage drop inside the source (Id Zi).
In case of a short circuit, Ud=0, therefore, the voltage at the source terminals Ui=0. Short circuit current Ik=Ei/Zi.
experimental external characteristic The source is removed by measuring voltage (Ui) and current (Id) with a smooth change in load resistance (Rd), while the arc is simulated by a linear active resistance - a ballast rheostat.
The graphical representation of the obtained dependence is the external static current-voltage characteristic of the source. When the load resistance decreases, the current increases and the source voltage decreases. Thus, in the general case, the external static characteristic of the source is falling.
There are welding machines with steeply falling, gently dipping, rigid and even increasing current-voltage characteristics. There are also universal welding machines, the characteristics of which can be steeply falling and hard.
External current-voltage characteristics of welding machines: 1 - steeply falling, 2 - gently falling, 3 - rigid, 4 - increasing.
For example, a conventional (normally dissipated) transformer has a rigid characteristic, and a rising characteristic is achieved by feedback, when the electronics increase the source voltage as the current increases.
In manual arc welding, welding machines with a steeply falling characteristic are used.
The welding arc also has a current-voltage characteristic.
First, with an increase in current, the voltage drops sharply, as the cross-sectional area of the arc column and its electrical conductivity increase. Then, with increasing current, the voltage almost does not change, since the cross-sectional area of the arc column increases in proportion to the current. Then, with an increase in current, the voltage increases, since the area of the cathode spot does not increase due to the limited cross section of the electrode.
As the arc length increases, the volt-ampere characteristic shifts upward. A change in the electrode diameter is reflected in the position of the boundary between the rigid and increasing sections of the characteristic. How larger diameter, the higher the current, the electrode end will be filled with a cathode spot, while the increasing section will shift to the right (in the figure below it is shown by a dotted line).
Stable arcing is possible provided that the arc voltage is equal to the voltage at the external terminals of the power source. Graphically, this is expressed in the fact that the characteristic of the welding arc intersects with the characteristic of the power source. The figure below shows three characteristics of the arc of different lengths - L 1 , L 2 , L 3 (L 2 >L 1 >L 3) and the steeply falling characteristic of the power supply.
The intersection of the current-voltage characteristics of the source and the arc (L 2>L 1>L 3).
Points (A), (B), (C) express the zones of stable burning of the arc at different arc lengths. It can be seen that the greater the slope of the source characteristic, the smaller the change in the welding current with fluctuations in the arc length. But the length of the arc is maintained during the combustion process manually, therefore it cannot be stable. That is why only with a steeply falling characteristic of the transformer, fluctuations in the tip of the electrode in the hands of the welder will not greatly affect the stability of the arc and the quality of welding.
When using the content of this site, you need to put active links to this site, visible to users and search robots.
Welding as a method of permanently joining metals entered our lives a little over a hundred years ago, but it is impossible to overestimate its importance today. With the help of welding, a significant number of various works are performed in various fields, from microelectronics to the manufacture of multi-ton structures. Since metals and alloys can have different shapes, sizes, and chemical compositions, a variety of related technologies, tools, and devices have been developed. But the main method has long and deservedly been considered electric welding (and sometimes cutting) of metals, primarily low-alloy steels. Among the advantages of electric welding is a fast and reliable connection of materials at minimal cost. However, if necessary, with the help of a welding machine, it is possible to cut metal, and even in hard-to-reach places where no other tool can fit. In recent decades, welding machines have been manufactured using electronic components, which significantly reduced their weight and dimensions and made it possible to further expand their use in everyday life.
Let's see what types of welding machines are and how they are distinguished.
WELDING POWER SOURCES
This is the main part of any welding machine, which converts the mains voltage into direct or alternating current with the specified parameters. Types of welding machines according to the type of power source are classified into:
Welding transformers. The traditional and at the same time structurally the simplest source of welding current. Its main node is the transformer itself, which lowers the mains voltage to welding. Regulate the current various methods, the most common of which is a change in the distance between the primary and secondary windings. All transformers have one thing in common - they produce alternating current at the output. In order to weld non-ferrous metals with the help of “trance” or to improve the stability of the arc, it is necessary to introduce additional heavy and bulky elements into the design, and the transformer itself weighs decently. At the same time, special electrodes for alternating current are required to perform critical work.
The efficiency of the transformer is quite high (up to 90%), but part of the energy is spent on heating. For cooling in modern models fans are also used of considerable power: after all, it is necessary to cool a device weighing several tens, or even hundreds of kilograms. Currently, this type of welding power source is used infrequently, but transformers, in addition to efficiency, have two more important advantages: low price and durability, because of which they are still in demand.
Welding rectifiers. Rectifiers are devices that convert alternating current to direct current. They consist of a step-down transformer, a rectifier (diode) unit, as well as adjustment, start-up and protection devices. This design, although more complicated than a transformer, provides much more stable output characteristics of the welding current and electric arc. The quality of the seam is also much higher in the end. The price of rectifiers is not much different from the price of transformers, reliability is also on top: there is practically nothing to break in them.
The main disadvantages are the same as those of the transformer - high weight, complexity of work, strong "drawdown" of the voltage in the network during the welding process.
inverters. This is the most modern type of welding machine. Unlike conventional welding machines, in which the power transformer operates at a mains voltage frequency of 50 Hz, the welding inverter uses a high frequency current (several tens of kilohertz). At the same time, a transformer of much smaller size and mass is required to transfer the necessary energy, and welding takes place at a good quality direct current, which also affects the quality of the seam. A conventional 160 A welding transformer weighs at least 18 kg, and a 160 A welding inverter power transformer weighs no more than 300 grams and is comparable in size to a pack of cigarettes, while the weight of the entire inverter, with a case and all electronics, is 3–7 kg. The inverter consists of a rectifier, network filter, a high frequency AC converter, a welding transformer, another rectifier and a control circuit. The welding inverter has a much wider welding current adjustment range than a conventional machine, which is especially important when welding with thin electrodes. Another "plus" - for inverters, as a rule, this adjustment is much more accurate and the output parameters are much more stable, which greatly simplifies the selection of the optimal operating mode.
*information posted for informational purposes, to thank us, share the link to the page with your friends. You can send interesting material to our readers. We will be happy to answer all your questions and suggestions, as well as hear criticism and wishes at [email protected]
Today, inverters are increasingly used for welding. Their production and sales are growing, their use is becoming commonplace. Inverter welders today can be found in a small workshop, on a large industrial enterprise, construction site or just in the household of a private house. What is their difference from ordinary (transformer) welding machines? Consider six parameters that are important for any device, and the differences between the inverter and traditional devices in these parameters. We especially note that Resanta welding machines are sold at the link http://www.avtogen.ru/svarochnye_invertory/brand-is-resanta/, see prices.
The quality of the resulting seam
It should be mentioned right away that the quality of the seam is most influenced by the professionalism of the welder, and not by the type of device used. However, with equal skills of the worker, such a feature of the inverter comes into play as the stability of the constant welding current, which does not depend on the supply voltage fluctuations. Accordingly, this current gives a more stable arc and a minimum of metal spatter. The seam will naturally be better.
Of considerable importance is the smooth regulation of the welding current, carried out in a fairly wide range. This allows you to choose the current in such a way that it is optimal for the specific parts to be welded and the electrode used. It is clear that a correctly set current will also affect the quality of the seam, all other things being equal.
Mobility, dimensions and weight
The inverter converts the alternating current of the network into direct current, which, using transistor circuits, is changed into high-frequency alternating current (about 50,000 Hz). This current is converted by a high-frequency transformer into a welding current that forms an electric arc. The principle used in inverters makes it possible not only to obtain excellent current-voltage characteristics, which make it possible to achieve high quality welding, but also to exclude a bulky power transformer from the design of the device.
Due to the use of high frequencies, the dimensions and weight of the transformer are reduced several times, and this leads to the fact that the weight and dimensions of the entire apparatus are reduced. For comparison - conventional welding machines (transformer type) weigh from 20-25 kg or more, and inverters - within 4-10 kg. It is clear that the mobility of the units with such a difference in weight does not make sense to compare, the inverter definitely wins in this parameter.
Power consumption
Compared to other types of welding machines, the inverter consumes relatively little energy and takes less time to work. When working with electrodes with a diameter of 3 mm, the consumption of a conventional welding machine is about 7 kW, and even the cheapest and simplest inverter is unlikely to exceed 4 kW. On Idling consumption goes down.
The main advantage is that energy is consumed only in the amount that is necessary for welding. Work with a 4 mm electrode can be carried out at a current value of 160A, however, with a supply voltage of about 180 volts, the quality will not be the best with such an electrode. In this case, you need a device of greater power or the use of electrodes of smaller thickness.
Efficiency
The efficiency of the inverter-type welding machine is above 90%, respectively, almost all the energy consumed goes into action, that is, it is used on the arc. The absence of a power transformer not only reduces the mass of the device, but also eliminates losses for the magnetization of iron cores, heating of the windings due to the mutual influence of magnetic fields. There is no power loss on the regulating shunt.
From this we can conclude that the efficiency of the inverter is clearly higher than the efficiency of conventional welders, losses tend to minimum values.
Price
Comparing the prices of welding machines, you can see that the cost of inverters has seriously approached the price of traditional devices. If earlier inverters were more expensive by 2 times or more, today the difference rarely exceeds 20%. Manufacturers from China played an important role here - the prices for their products have always been highly competitive.
Reliability and unpretentiousness
The electronic control of the inverters provides a reliable feedback of the parameters of the arc current with the output properties of the device - when ignited, the device creates an additional impulse that facilitates the formation of an arc. A short circuit almost instantly turns off the welding current - this eliminates the effect of "sticking" of the electrode. Ease of operation, reliability of the device benefit from this.
Their sensitivity to dust and humidity negatively affects the operation of inverters. It is necessary to protect the inside of the appliance, if possible, from dust entering through ventilation holes It is a good idea to periodically clean the device. Store the inverter in a warm, dry place to prevent moisture from forming on the board elements.
The inverter device does not tolerate drops and shocks very well, due to the presence of electronic filling. In terms of unpretentiousness, this type of welder loses to conventional welding transformers.
If necessary independent holding welding work, the question arises: what type of welding machine to purchase. Welding is the creation of permanent connections between the parts to be welded at the atomic level. The welded joint is one of the most durable and therefore is used quite often.
In electric welding, heating and melting of the metal occurs due to the formation of an electric arc between the end part of the electrode and the surface to be welded. Sources of formation and maintenance of the arc are divided into several types:
- Transformer.
- Inverter.
- Rectifiers.
- Welding units based on an internal combustion engine.
Consider the two types that have found the most widespread use: a transformer-based welding machine and an inverter source of an electric arc.
This is the simplest of the welding machines, using the alternating current of the network. Works at the expense of the transformer which regulates tension of a network to welding. Transformer or induction welding machines are divided according to the following features:
- Power (the greater the welding current, the thicker the metal can be processed).
- The number of posts, that is, jobs (how many people can work at the same time).
- Voltage (single-phase or three-phase network).
It has the advantage of being simpler and robust construction, low cost, high maintainability.
The disadvantages include the dependence of the arc on power surges, large weight and overall dimensions, strong heating during work.
What is an inverter?
An inverter welding machine or simply an inverter is one of the energy sources for electric arc welding, which is based on use of high frequency current. Its work is carried out due to power electronics and a small transformer.
Its advantages are recognized as low power consumption, compactness, small weight and dimensions, and a sufficiently high quality of the seam.
The disadvantages of the inverter include relatively high cost, fear of moisture, dust and low temperatures (typical for budget models), sensitivity to power surges, expensive repairs.
What do inverter and transformer welding machine have in common
The similarity of these devices in their purpose is the formation and maintenance of an electric arc. But there are some other things that they have in common:
- The devices under consideration are united by the presence of a transformer, but different sizes. By pre-acquiring high frequency current, the inverters do not require large transformers. To obtain a current of 160 A, a transformer weighing 0.25 kg is needed. To obtain the same current in inductive devices, a transformer weighing 18-20 kg is required.
- Possibility of smooth adjustment of current. Transformer devices have such an opportunity due to a change in the size of the air gap in the magnetic circuit.
- The devices are powered by household (220V) or industrial (380V) mains.
- Most welding machines have short circuit protection.
What is the difference between inverter and transformer source of electric arc
- The dimensions and weight of the transformer type welding machine are larger than those of the inverter. Industrial designs can weigh more than one hundred kilograms.
- Operating principle. In the inverter, the alternating current of the network is converted by the primary rectifier into direct current, then again into high-frequency alternating current, and then again there is a change to direct current at the secondary rectifier. For transformer-type welding machines, the current strength changes due to a change in the position of the magnetic circuit, that is, the core of a step-down transformer or the inclusion of a different number of turns of windings in the circuit.
- The inverter has a more stable arc due to the stability of the welding current, which affects the quality of the seam.
- Design difference. The inverter is more complex and can be equipped with the following additional features: HOT START– increase in the initial current to improve the ignition of the welding arc. ARC FORCE- an increase in the welding current to accelerate the melting process and prevent sticking, that is, the arc is forced. ANTI STICK- reduction of current when the electrode sticks to increase the time for its separation and protection against overload.
- The process of learning to work on a transformer is more complex and time-consuming. However, having mastered these skills, you can easily work on an inverter.
- The inverter produces a direct current, the transformer operates on an alternating current with a household power supply frequency of 50 Hz.
- The power factor of the inverter is the largest of all welding equipment, and the efficiency exceeds transformer analogues by 20-30%.
- Wide range of welding current.
- The inverter has such an indicator as the coefficient of intermittent operation (KP). It determines the time of continuous operation at maximum welding current. That is, if the CP is 50%, then after 10 minutes of operation it needs 5 minutes to cool down. There are no such requirements for a transformer welding machine.
- Possibility of using electrodes designed for both direct and alternating current.
To date, the market has a fairly wide selection of welding equipment from various manufacturers. The choice of welding machine should be made on the basis of the tasks that are to be performed with its help.
