Comparison Tesla Weld MMA 235 vs Tesla Weld MMA 251

The minimum actual input voltage at which the welding machine remains operational.

Such information is useful primarily for working in unstable networks, where the voltage tends to “sag” a lot, as well as from autonomous power sources (for example, generators), which can also produce voltage below the nominal one.

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.

The voltage supplied by the welding machine to the electrodes. As the name suggests, it is measured without load — i.e. when the electrodes are disconnected and no current flows between them. This is due to the fact that at a high current strength characteristic of electric welding, the actual voltage on the electrodes drops sharply, and this does not make it possible to adequately assess the characteristics of the welding machine.

Depending on the characteristics of the machine (see "Type") and the type of work (see "Type of welding"), different open circuit voltages are used. For example, for welding transformers, this parameter is about 45 – 55 V (although there are higher voltage models), for inverters it can reach 90 V, and for semi-automatic MIG / MAG welding, voltages above 40 V are usually not required. Also, the optimal values \u200b\u200bdepend on type of electrodes used. You can find more detailed information in special sources; here we note that the higher the open-circuit voltage, the easier it is usually to strike the arc and the more stable the discharge itself.

Also note that for devices with the VRD function (see "Advanced"), this parameter indicates the standard voltage, without reduction through VRD.

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”.

The highest current that the welding machine is capable of delivering through the electrodes during operation. In general, the higher this indicator, the thicker the electrodes the device can use and the greater the thickness of the parts with which it can work. Of course, it does not always make sense to chase high currents — they are more likely to damage thin parts. However, if you have to deal with large-scale work and a large thickness of the materials to be welded, you simply cannot do without a device with the appropriate characteristics. Optimum welding currents depending on materials, type of work (see "Type of welding"), type of electrodes, etc. can be specified in special tables. As for specific values, in the most “weak” models, the maximum current does not even reach 100 A, in the most powerful ones it can exceed 225 A and even 250 A.

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%.

The largest diameter of the electrode that can be installed in the welding machine. Depending on the thickness of the parts, the material from which they are made, the type of welding (see above), etc. the optimal electrode diameter will be different; there are special tables that allow you to determine this value. Large diameter may be required for thick materials. Accordingly, before purchasing, you should make sure that the selected model will be able to work with all the necessary electrode diameters.

In modern welding machines, an electrode diameter of 1 mm or less is considered very small, 2 mm — small, 3 mm and 4 mm — medium, and powerful performant models use electrodes of 5 mm or more.

— Hot start. A function that facilitates arc ignition: when the electrode touches the welding spot, the welding current increases for a short time, and when the machine enters the mode, it returns to standard parameters.

— Forcing the arc (Arc Force). Devices with this function are able to increase the welding current with a critical reduction in the distance between the electrode and the parts to be welded. This increases the rate of melting of the electrode and the depth of the weld pool, which helps to avoid sticking.

— Protection against sticking (Anti-Stick). In this case, a protective measure is implied in case sticking of the electrode still could not be avoided: the automation of the welding machine significantly reduces the welding current (or even turns it off), which makes it easy to disconnect the electrode, and in addition — to avoid unnecessary energy consumption and overheating devices.

— Decreased voltage x. X. (VRD). This function is used to significantly reduce the open circuit voltage of the machine. When the VRD is turned on, the open electrodes receive not a standard voltage of several tens or even hundreds of volts, but only 9-12 V. At the same time, the operating parameters are restored automatically — when the electrode touches the workpiece and a high current occurs; and when the arc is e...xtinguished, the voltage again drops to the minimum values. This format of work provides two main advantages. Firstly, it provides additional safety: in particular, closing contacts with a hand or other part of the body does not lead to a serious electric shock, and the risk of such an injury in high humidity is also reduced. Secondly, lower voltage helps to save energy.

— Pulse welding. Usually, this refers to gas-shielded arc welding (MIG / MAG or TIG), carried out in the so-called pulsed mode. With this format of operation, the main welding current, which is relatively low, is supplemented by high-power pulses (7-10 times higher than the background current), which follow at a frequency of several tens per second. There are also various modifications of the pulse mode, with more complex current control; however, the basic principle remains the same. Anyway, the advantages of pulsed welding are the uniformity of both the arc itself and the resulting seam, as well as an improvement in the overall quality of the joint: pulses help to mix the metal in the weld pool and eliminate pores, oxides and other defects. The disadvantage of this function is traditional — an increase in the cost of welding machines.

— 2/4-stroke mode. Possibility to choose the control mode of the device — two-stroke or four-stroke. This allows you to further adjust the control to the specifics of the situation. Recall that in push-pull mode, the device works while the button is pressed, and turns off when it is released; this is especially useful for short seams and other similar tasks when welding does not need to be switched on for a long time. In turn, with a four-stroke control format, the first press-release turns on welding, the second turns it off. This method is indispensable for long-term work, when it would be tiring to keep the button pressed all the time.

— Synergetic management. A function mainly used when operating in the pulse mode described above. Synergic control can also be called "intelligent": it is carried out using built-in electronic microcontrollers that control most of the settings and automatically change them if necessary. In fact, it looks like this: it is enough for the welder to set a number of inputs (type and thickness of the material, composition of the shielding gas, wire thickness, etc.), and based on this, the machine will automatically select the optimal operating parameters (output voltage, pulse configuration, feed rate wire, etc.). Moreover, if one of the inputs changes in the course of work, the other parameters of the work change accordingly.
Synergic control greatly simplifies the operation of the device and at the same time improves its quality, reducing the likelihood of burns and other serious errors. This is especially convenient for inexperienced welders who are not accustomed to dealing with fully manual parameter settings; however, even professionals appreciate the ease and speed of adjustment that is characteristic of synergic models. The main disadvantage of this feature is that it has a significant impact on the cost.

— Digital display. The presence of its own display in the design of the welding machine. This is, usually, the simplest segment screen, designed to display 2 – 3 digits and some special characters. However, even such screens are more informative than light and other similar signals: they can display a wide variety of data (input and operating voltage, time until shutdown "to rest", error codes, etc.). And the advantages over dial indicators are in small size and versatility — the display can display different types of information. As a result, this function can greatly simplify the work with the welding machine.

— Connector for the remote control. Connector for connecting a remote control to the device. Depending on the model, we can talk about both traditional hand controls and foot pedals. Anyway, such an accessory provides additional convenience in some situations — in particular, it allows you to turn the power on and off, and even change individual operation parameters, without approaching the device every time. However most often welding machines are supplied without a remote control — however, this gives certain advantages: you can choose such an accessory at your discretion (the main thing is to make sure it is compatible).

— Liquid cooling. Presence of a liquid cooling system in the configuration of the welding machine. Such cooling is more efficient than air cooling, it intensively removes heat from the hardware of the apparatus, the burner and allows you to achieve a very high duty cycle (see above) — up to 100%, and at currents of 200 A or more. Its disadvantages are complexity, high cost, bulkiness and significant weight. In light of the latter, liquid cooling units are often made separately from the welding machines themselves and can be connected / disconnected depending on what is more important at the moment — efficient cooling or portability. Also note that for many models, the manufacturer recommends using specialized coolants, and they are most often not included in the delivery set.

— Built-in compressor. Compressor for air supply built directly into the machine. This feature is found only in models operating in PLASMA mode. Recall that this mode involves cutting metal using a powerful jet of highly heated and ionized air; To create the desired pressure, a compressor is needed. It can also be external; however, the built-in compressor allows you not only to always have all the necessary equipment with you, but also to reduce the overall dimensions of this equipment. In addition, with such equipment, you do not need to worry about the compatibility of the device and the air supply system. The disadvantages of models with built-in compressors include the increased cost, as well as the dimensions and weight of the entire body.

— Starting the car engine. The ability to use the device to start the car engine, namely to power the starter. In other words, models with this function are also able to work in the launcher mode. Such an opportunity will be useful if the regular car battery is dead, out of order or missing, but there is a power source (mains or generator) nearby from which you can power the welding machine. Note that most often in this case it means the launch of cars with 12-volt on-board networks — cars, light trucks and buses; however, technically, nothing prevents to provide compatibility with heavy equipment (trucks, buses) operating on 24 volts. These details should be specified separately.

— Transport wheels. The presence in the design of the welding machine of special wheels that facilitate transportation. The weight of some modern models can reach several tens of kilograms, and it is difficult even for several people to carry such a device manually. The presence of wheels makes it possible to manage by the forces of one person, even with a significant weight of the unit.

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.