Type
The type of welding machine determines the features of its design and purpose.
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Transformer. The simplest type of welding machine. The principle of operation in this case is as follows: the input mains voltage is fed directly to the transformer winding, which lowers it to the open circuit voltage (see below). In addition to alternating current, transformers can also cook on direct current — in such models, the simplest rectifier with a stabilizer is usually used; when using alternating current, its frequency remains the same as in the network. The main advantages of transformers are high reliability combined with low cost and simplicity of design. At the same time, the functionality of such devices is rather limited — in particular, of the types of welding, there are rarely any other than manual arc welding (see "Type of welding"); and the quality of work is relatively low due to the instability of the current supplied to the electrode. Yes, and the weight of transformers, compared with inverters, is quite high. In general, this type of welding machine is intended mainly for simple work that does not require high precision.
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Inverter. A type of welding machine designed to overcome some of the major disadvantages of transformers, such as heavy weight and uneven seams. The key difference between inverters is that the current to the winding of the step-down transformer is not supplied direc
...tly from the network, but through special control circuits (which, in fact, are an inverter in the narrow sense of the word). When passing through these circuits, the current is first converted to direct, and then back to alternating, but with an increased frequency of the order of tens of kilohertz (for comparison, the frequency of household alternating current is 50 Hz), and this high-frequency current is already supplied to the winding. This made it possible to significantly reduce the dimensions of the transformer coils and thus reduce the weight and dimensions of the entire device — many inverters can be safely carried on a shoulder strap. A high frequency provides a much more stable arc and a quality weld both when welding with alternating current and when using direct current (for both options, see the “Welding Current” paragraph for more details). In addition, this scheme allows the use of almost all modern types of welding (see below). Among the disadvantages of inverter devices, one can note the high cost due to the complexity of the design. However, if you need a device for high-quality professional welding, you cannot do without an inverter.
— Semiautomatic. This term refers to a type of welding transformers (see above), in which the welding process is partially automated. The electrode for a semiautomatic device has the form of a thin wire (usually not thicker than 1.2 mm) wound on a coil; during operation, this wire is fed to the nozzle automatically, as it is consumed. This is much more convenient than with conventional welding — after all, the operator does not have to control the length of the electrode himself and adjust it manually, the electrode itself has to be changed much less often, and semi-automatic welding also has some other advantages (for more details, see "Type of welding"). Otherwise, semiautomatic devices are completely similar to conventional transformers.
— Semi-automatic inverter. As the name implies, this category includes inverter-type machines with an electrode supply system typical for semi-automatic machines. For more details, see the relevant paragraphs above, but here we note that this option can be called the most advanced among modern general-purpose welding units.Welding current
The type of current used by the machine directly in the welding process.
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Variable. A kind of current that is familiar to many primarily from ordinary household sockets: it has an interchangeable polarity, the “plus” and “minus” on the contacts change places with a high frequency. For example, in a household network, the frequency is 50 Hz, and at the output of inverter devices (see "Type") it can rise to several tens of kilohertz. The main advantage of alternating current is that the concept of “polarity” does not apply to it and it is impossible in principle to confuse it when connected. At the same time, the constant reversal of the current direction increases the amount of welding spatter and reduces the quality of the weld. This shortcoming is partially eliminated in the mentioned inverters, due to high frequency currents, however, the quality of welding with alternating current is still somewhat lower than when using direct current. As a result, this option is most widely used in manual arc welding (see "Type of welding") of ferrous metals, in other cases it is rare or not used at all.
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Permanent. A current that has a constant direction — from one pole to another, without changing them (similar to how this happens, for example, when using batteries). Such a current, due to its uniformity, creates much less spatter than alternating current, and provides a better quality of the seam.
...It is also better suited for stainless steel, non-ferrous metals and some specific applications (eg semi-automatic welding, see Welding type). However, as for batteries, the concept of polarity is relevant for direct current devices: “minus” can be connected both to the electrode (so-called direct polarity) and to the material being welded (respectively, reverse). Each of the options is used for certain materials and types of work, so when using direct current, you also have to pay attention to the correct connection. In addition, the direct current devices themselves are more complicated and expensive due to the need to use rectifiers.
— Variable/constant. Devices capable of using both of the above types of current in operation. They are the most versatile, however, and cost accordingly.Power consumption
The maximum power consumed by the welding machine during operation, expressed in kilowatts (kW), that is, thousands of watts. In addition, the designation in kilovolt-amperes (kVA) can be used, see below for it.
The higher the power consumption, the more powerful the current the device is capable of delivering and the better it is suitable for working with thick parts. For different materials of different thicknesses, there are recommendations for current strength, they can be clarified in specialized sources. Knowing these recommendations and the open circuit voltage (see below) for the selected type of welding, it is possible to calculate the minimum required power of the welding machine using special formulas. It is also worth considering that high power creates corresponding loads on the wiring and may require connection directly to the shield.
As for the difference between watts and volt-amperes, the physical meaning of both units is the same — current times voltage. However, they represent different parameters. In volt-amperes, the total power consumption is indicated — both active (going to do work and heat individual parts) and reactive (going to losses in coils and capacitors). This value is more convenient to use to calculate the load on the power grid. In watts, only active power is recorded; according to these numbers, it is convenient to calculate the practical capabilities of the welding machine.
Min. welding current
The smallest current that the device is able to supply through the electrodes during operation. For different materials, different thicknesses of the parts to be welded and different types of welding itself, the optimal welding current will be different; there are special tables that allow you to determine this value. The general rule is that a high current is far from always useful: it gives a rougher seam; when working with thin materials, it is possible to melt through the junction instead of connecting the parts, not to mention excessive energy consumption. Therefore, if you have to work with parts of small thickness (2-3 mm), before choosing a welding machine, it makes sense to make sure that it is capable of delivering the desired current without “busting”.
Duty cycle
The duty cycle allowed for the welding machine.
Almost all modern welding machines require breaks in operation — for cooling and general "recovery". The frequency of inclusion indicates what percentage of the time of the total work cycle can be used directly for work. In this case, 10 minutes is usually taken as a standard cycle. Thus, for example, a device with a duty cycle of
30% will be able to work continuously for less than 3 minutes, after which it will need at least 7 minutes of interruption. However, for some models, a cycle of 5 minutes is used; these nuances should be clarified according to the instructions.
In general, high frequency is required mainly for high-volume professional work; with a relatively simple application, this parameter does not play a decisive role, especially since you have to take breaks during work. As for specific values, the mentioned 30% is a very limited figure, typical mainly for entry-level devices. A value of
30 – 50% is also low; in the range of
50 – 70% is the majority of modern devices, and the most "hardy" models provide a frequency
of more than 70%.
Protection class (IP)
The protection class to which the housing of the welding machine corresponds.
This parameter is traditionally denoted by the IP standard with two digits. It characterizes how well the case protects the hardware from foreign objects and dust (first digit), as well as from moisture (second digit). It is worth noting that in welding machines the degree of such protection is usually small — this is due to the fact that the case must be made ventilated. Here are the levels of protection against solid objects / dust that are relevant for modern models:
1 — protection against objects larger than 50 mm (comparable to the size of a human fist or elbow);
2 — from objects larger than 12.5 mm (we can talk about protection from fingers);
3 — from objects larger than 2.5 mm (the probability of accidental hit by most standard tools is excluded);
As for protection against moisture, it can be generally zero — that is, such a device can only be used in dry conditions. However, there are more advanced options:
1 — protection against drops of water falling vertically, with a strictly horizontal position of the device (the minimum degree of protection, in fact — from accidental ingress of a small amount of moisture);
2 — from vertical drops of water when the device deviates from the horizontal up to 15 ° (slightly higher than the minimum);
3 — from splashes falling at an angle of up to 60 ° to the vertical (we can talk about protect...ion from rain);
4 — from splashes falling from any direction (possibility of use in rain with strong winds);
Sometimes, instead of one of the numbers, the letter X is put — for example, IP2X. This means that the protection class for the corresponding type of exposure is not defined. In such a case, it is best to assume that there is no protection at all — this will provide maximum security and avoid unpleasant surprises.
