Welding machines of inverter type

Understanding Inverters: Classifying and Selecting the Right Inverter Welding Machine
Discover the features and distinctions of welding inverters vs transformers. Explore the various types of inverter welding machines. Find the perfect inverter for residential, vacation home, or professional applications.

Electric arc welding is a highly effective and efficient method for connecting metal parts. This technique has been widely utilized for over a century, making it a time-tested solution. The process involves melting the edges of the metal elements and then filling the gaps with molten metal from a welding electrode, all while being powered by an electric current. In the past, this was achieved through the use of large power transformers, which would lower the network voltage to the required 50-60 volts. However, nowadays, inverter welding machines are the norm, as they come equipped with advanced technology and offer a wide range of technical capabilities.

The principle of operation of the welding inverter

The major distinction of the inverter-type welding machine lies in its more intricate series of conversions that the standard alternating electric current, with a 50 Hz oscillation periodicity and a 220-volt voltage, undergoes before being supplied to the electrode. Initially, it is rectified and smoothed through the passage of a specialized filter. Next, by swiftly opening and closing transistors, it is inverted into an alternating current with an oscillation frequency that can reach tens of kilohertz. Only after this stage, the current is transformed into the necessary 100-200A for welding, with a voltage of 50-60V. At the output, a high-frequency rectifier operates in order to achieve the constant current that is essential for high-quality welding. The transistorized control unit is responsible for controlling and adjusting the outgoing parameter values of the welding inverter. It shapes the optimal characteristics of the current that flows to the electrode, which are necessary for any type and mode of welding.

An inverter differs from a welding transformer in that it converts low-frequency currents through a power transformer, which is only available in larger devices, while high-frequency inverter equipment is known for its compactness and minimal use of materials.

Advantages of inverters

1. With a weight of less than 10 kg and a compact size, most models of inverter welding machines are easily stored and transported.
2. The inverter’s efficiency is significantly improved by the absence of heat losses from heating the windings. In fact, it consumes about 1.5 times less energy than a typical welding transformer or rectifier.
3. The universal inverter offers a wide range of settings, making it suitable for welding stainless steel and non-ferrous metals.
4. Even the models designed for home and cottage use don’t require long breaks to cool down the machine.
5. The inverter welding machine is equipped with a user-friendly control system that allows for smooth adjustment of all necessary parameters. This means even a beginner welder can achieve high-quality welds.

There are some drawbacks associated with inverters, such as their relatively high cost and the need for specific storage and operating conditions. In addition, these devices are susceptible to issues caused by dust, excessive humidity, and low temperatures.

Classification

When it comes to production needs, a variety of inverters with different functional features are utilized:

• Manual electric arc welding (MMA) inverters;
• Inverters for argon welding with tungsten electrode;
• Semi-automatic welding inverters for inert or active gas atmosphere (MIG/MAG);
• Semi-automatic machines that can be used in MMA and MIG/MAG modes;
• Universal inverters suitable for various modes of operation;
• Air-plasma cutting units.

Based on their performance level and technical characteristics, inverters for working with fusion electrodes can be roughly categorized into three major groups.

Household mini-models are designed for home and cottage use, and they come with basic equipment and affordable prices. These inverters are suitable for occasional use.

WESTER MINI200 welding inverter

The professional welding inverter Wester Wz7 400 is ideal for all your welding needs.

What to pay attention to when buying an inverter

The selection of a welding inverter depends on the welding conditions and the required modes. One of the primary factors to consider is the input voltage. Most devices are designed to operate on 220 volts, but there are also models that can be connected to a 380-volt network. The acceptable input voltage range is typically specified in the device’s documentation, such as 220V + 15% – 30% or 160-240V. This is especially important in rural areas with frequent voltage fluctuations.

The primary characteristic that should be considered when selecting a welding mode is the welding current. The welding current is directly influenced by the thickness of the parts being welded and the diameter of the electrodes being utilized. For household welding tasks, it is rarely necessary to weld products that are thicker than 10 mm. In these cases, it is recommended to choose an inverter that is capable of producing a current of 160-180 A. When welding carbon steel sheets that are up to 20 mm thick, it is important to anticipate a current of 200 A. It is advisable to only purchase more powerful welding units for specialized workshops. The method of adjustment is also a significant factor to consider. The ability to smoothly regulate the welding current, as opposed to discrete adjustments, is always preferable in order to achieve a high-quality weld.

Tip! When working with thin parts, it is important to pay attention to the minimum outgoing current. It is desirable for the lower limit of the outgoing current to be around 10 A.

The ease of igniting the welding arc depends on the idle voltage. In most models, this voltage ranges from 40 to 90 volts. The higher the voltage, the easier it will be to perform welding.

In situations where the welding machine is used intensively, the percentage of operating time at maximum current, known as SP, greatly impacts the machine’s performance. A high-quality machine should have an SP indicator of at least 70%. This means that out of a 10-minute production cycle, 7 minutes can be used for welding at full capacity, while the remaining 3 minutes can be used for replacing the electrode, cleaning the seam, and cooling the device.

Additional functions realized on welding inverters

The implementation of microprocessor control in inverter equipment with efficient feedback enables the realization of additional features that enhance the welding process. These features include:

• Hot start, which involves a brief voltage increase during the initial welding phase to facilitate arc ignition;
• Anti-sticking, which greatly reduces the load when the electrode accidentally contacts the surfaces to be welded, preventing electrode sticking, a common issue for inexperienced welders;
• Arc afterburner, which prevents electrode sticking when a large droplet of molten metal separates from the electrode due to a temporary current increase.

The convenience of working with inverter welding machines and the quality of the resulting seams are both positively influenced by the aforementioned properties.