what is an inverter welder

Inverter welding current source

                        inverter welder vs transformer:

An inverter welding current source (IIST, Welding inverter) is one of the modern types of welding arc power supply.

Inverter sources of welding current for all types of welding are arranged in the same way. The difference is only in the generated current-voltage characteristic.

Therefore, it is possible to produce universal IIST suitable for various types of welding (MMA, TIG, MIG/MAG).

History:

The main purpose of all welding sources is to ensure stable garage welding arc and its easy ignition.

One of the most important parameters of the welding process is its resistance to vibrations and interference. There are several types of welding arc power sources — transformers, diesel or gasoline power generators, rectifiers and inverters.

The inverter welding current source appeared in the XX century, and at the beginning of the XXI century it became one of the most popular welding machines for all types of arc welding.

The principle of operation

The welding inverter is a power transformer for lowering the mains voltage to the required no-load voltage of the source, a block of power electrical circuits based on MOSFET or IGBT transistors and a stabilizing choke to reduce the ripple of the rectified current.

The principle of operation of inverter source of the welding arc the following: the mains voltage AC is supplied to the rectifier, after which the power module converts DC to AC with high frequency, which is applied to high frequency welding transformer, which can have a much smaller mass than the network voltage which, after rectification, is fed to the welding arc. The DC arc is more stable.

Advantages

The advantage of the inverter power supply of the welding arc is to reduce the size of the power transformer and improve the dynamic characteristics of the arc.

The use of inverter technologies has led to a reduction in the size and weight of welding machines, an improvement in the quality index of the welding arc, an increase in efficiency, minimal spatter during welding, and allowed for smooth adjustments of welding parameters.

Disadvantages

Until the late 2000s, inverter sources were much more expensive than transformer sources and less reliable.

As of the 2010s, the price of inverter devices has significantly decreased and approached the transformer ones. The reliability of the IIST has also increased significantly, especially with the beginning of mass use of IGBT modules.

Limited load factor, which is associated with significant heating of the circuit elements.

Increased sensitivity to air humidity and condensation falling out inside the housing.

The high (and often dangerous) level of high-frequency electromagnetic interference generated.

This problem is partially solved by the use of so-called improved pulse width modulation and synchronous rectifiers in secondary circuits.

However, these solutions significantly increase the cost and weight of the device, so they are used only in professional stationary models. In a number of countries, for example, in Canada, Belgium and the Netherlands, there are restrictions on the use of switching power supplies with “hard” switching transistors.

The earliest types of welding inverters (built on bipolar transistors) used the resonant principle and switching of the output transistors at zero phase current, which significantly narrows the spectrum of electromagnetic interference and reduces their spectral power.

As of 2015, resonant type welding inverters are still produced in Russia and by some manufacturers in China.

Circuit design

Inverter sources of welding current can be built according to a variety of schemes, but in practice, three prevail:

Single-stroke direct-flow pulse converter with PWM regulation and energy recovery.

Such inverters are the simplest, lightest and most compact, but power transistors switch with a current gap at a non-zero voltage, which leads to significant switching losses and a large level of electromagnetic interference.

The scheme can be implemented only on high-speed high-power MOSFET or IGBT transistors, so it became widespread only in the early 2010s. Also, the circuit requires powerful diodes with extremely short reverse recovery time.

The efficiency of the circuit largely depends on the intensity of transients on the parasitic capacitance and inductance of components, wires and printed circuit boards, which requires careful design and high manufacturing accuracy.

The scheme is used in portable welding machines designed for low power (up to 4 kW). Despite the small number of components, such inverters are quite expensive, and 60-70% of the cost is made up of special transistors and diodes. The scheme is common among European and Japanese manufacturers.

Semi-bridge or bridge push-pull converter with PWM control. The switching losses and the level of electromagnetic interference in them are less than in the previous type, but still quite high.

The circuit is more complex and requires more components, but the power developed by the converter is significantly higher than in single-stroke circuits (up to 10 kW).

High-speed MOSFETs or IGBTs with a high permissible pulse power dissipation, although less than in a single-cycle circuit, are also required.

The requirements for diodes are also significantly lower than in a single-cycle circuit. The efficiency of the circuit depends, but to a lesser extent than that of single-cycle circuits, on the intensity of transients on the parasitic capacitance and inductance of components, wires and printed circuit boards.

The flexibility, speed and precision of PWM control allows you to control the arc current according to complex laws, which improves the quality of welding. The scheme is popular with American and Korean manufacturers.

Half-bridge or bridge resonant converter with frequency or phase control. The presence of a specially introduced resonant circuit makes it possible to form an optimal switching path of transistors at zero voltage or zero current, as well as to neutralize the influence of parasitic capacitances and inductances.

There are no special requirements for the switching speed and power of transistors, since switching processes occur passively.

This makes it possible to build such inverters using inexpensive transistors and diodes. Even bipolar transistors are suitable.

The power of resonant inverters can reach tens of kilowatts. However, the resonant circuit must have a significant energy consumption and, accordingly, large dimensions.

Therefore, such devices are quite large and heavy. Due to the low demand of resonant converters for the characteristics of transistors, the price of such products can be relatively low.

For this reason, most of the welding inverters produced in Russia and China are made using resonant circuitry.

Resonant transducers are also available for artisanal production. The resonant converter has a relatively narrow range and a low speed of regulation, so it is possible to implement only relatively simple laws for controlling the arc current.

Types of welding equipment

  • Welding Rectifiers
  • How to make a welding transformer with your own hands.
  • How to calculate the winding.
  • Self-made arc or contact welding machine

Welding transformer: construction and principle of action

What to choose: welding transformer or welding inverter

Metal welding is used in many industries, construction and even in solving small household issues. To make a smooth seam, you need to have the skills and equipment.

Welding equipment is all that a welder needs to work with. These are special welded devices, protective elements, and consumables.

Using all this, you can combine most of the metals at the molecular level. The final product is strong, and will serve for a long time.

The type of welding machine depends on the welding technology that the employee must possess. The choice of welding method depends on the task at hand.

Specialists use the following types of mechanisms:

Welding transformers. A kind of classic among welding machines. The transformer is a reliable and simple device. Working with it, you can connect thick steel sheets, because the strength of the welding current of the transformer for such purposes is quite enough.

The transformer converts the mains voltage to low. Now inverters are much more common than transformers. However, experienced welders still appreciate transformers.

This equipment is used for manual arc welding with electrodes. The large weight and considerable dimensions, which will cause difficulties with the movement, are considered disadvantages.

Inexperienced welders may also encounter unstable burning of the arc.

Welding inverter. A new-generation welding machine that novice welders can work with. Compactness, a lot of parameters and a good selection of units on the market-these are the main advantages of the inverter.

Inverters that are designed for welding in a protective gas environment are called semi-automatic. The functions “arc afterburner”, “hot start” and “anti-jamming” are available in almost all modern inverters.

Welding generators: The inverter can perform simple repairs and quickly weld a small part, but without electricity, it is completely useless.

A gas line or diesel generator solves this problem by providing an autonomous power supply, which is important for construction work in an area where there is no electrical network.

A welding unit is a generator and a welding machine in one housing. That is, to work with welding equipment, it is not necessary to have an electrical network.

The device runs on a single fuel. It is inexpensive and compact, and the quality of the seams obtained by using generators is quite high. But to use the device to the full, you will need to buy a rectifier.

Welding rectifiers: The equipment is called a classic of welding on a par with transformers. The rectifiers convert alternating current to direct current, which is then used to create the weld.

This is their peculiarity. Usually, this type of equipment consists of a power part and a rectifier unit, as well as protective, starting and adjusting elements.

Arc welding machines: The advantage of rectifiers is reliability and power. The absence of electronics reduces the likelihood of breakdowns. If desired, such a device can be assembled at home.

Welding machines: Automation allows you to significantly reduce labor costs. The machine also helps the worker to control the correct creation of the seam.

The electrodes are not required for automatic welding, instead, the filler wire is used, which is fed automatically to the working area.

Welding Rectifiers:

The principle of operation of rectifiers is simple. First, the device reduces the mains voltage of 380V to the no-load voltage, then converts alternating current to direct current. Controlled welding current can be used during welding operations.

The main difference between a rectifier and a transformer: the former uses direct current to create a weld, while the transformer uses alternating current.

In other respects, both types of welding equipment can be called similar. Some welders even claim that the rectifier is the same transformer, only it is easier to use.

The advantage of the rectifier is the ability to operate in any conditions. The same inverter is not designed to work in dirt and dust, and for a rectifier, such circumstances do not matter.

It is also great for performing complex welding operations, such as welding stainless steel or non-ferrous metals.

In skilled hands, the arc burns steadily, which makes it possible to make smooth and accurate connections.

Most welding technologies can be used with rectifiers: MMA, TIG, MIG or MAG. Another advantage is the ability to create several welding stations using only one rectifier, which will allow several specialists to work simultaneously.

However, there are three significant drawbacks to rectifiers:

A lot of weight. This often does not allow you to move the equipment yourself.

High cost of additional elements. The rectifier itself does not cost very much, but a complete set of all the necessary equipment can cost a considerable amount. It is also necessary to prepare for high energy costs.

The need for a certain skill of the employee. Beginners will not be very comfortable working with such a device, but after constant practice with the rectifier, a novice specialist will master any welding equipment.

The best choice for home use. Most often, they are also equipped with functions for recharging the car battery. Sometimes in the complete set there are devices for feeding the wire, which is required for MIG/MAG welding (semi-automatic). Such welding devices do not require a lot of electricity.

They are very practical. Such devices usually have three modes of operation:

Charging of batteries (battery). Voltage 12 or 24 V.

Starting the car engine. The maximum inrush current is 250 A for 12V and 200 A for 24V.

Welding. The current is regulated from 30 to 180 A, the discontinuity rate of modern welders is measured as a percentage. That is, a factor of 60% means that the arc will burn continuously for 6 minutes out of 10.

A large part of the welding equipment has overload protection and digital ammeters.

How to make a welding transformer with your own hands. How to calculate the winding. Self-made arc or contact welding machine

How to make a welding transformer with your own hands. How to calculate the winding. Self-made arc or contact welding machine

Metal welding is used in many industries, construction and even in solving small household issues. To make a smooth seam, you need to have the skills and equipment.

Welding equipment is all that a welder needs to work with. These are special welded devices, protective elements, and consumables. Using all this, you can combine most of the metals at the molecular level. The final product is strong, and will serve for a long time.

The type of welding machine depends on the welding technology that the employee must possess. The choice of welding method depends on the task at hand.

 

 

 

 

Leave a Reply

Your email address will not be published. Required fields are marked *