Inverter vs Transformer Welding Machines. Which one is best?

In this article

Inverter vs Transformer Welding Machines. Which one is best?

Spread the knowledge


When reading the title of this article: inverter vs transformer welding machines, it might look like we were really bored on a Sunday afternoon and we started to think about the solution to a problem already solved.

But the truth is that until now, there is a hot debate among professional welders around the pros and cons of these two systems. One has been there for decades, and the other looks like the new kid on the block.

A hot debate

Basically, this debate between inverter vs transformer welding machines is a matter of attaching to a tradition or jumping to the innovation. Since transformer welding machines have been out there like forever, some experts feel that we should keep using them, because otherwise, it would be saying goodbye to reliability.

On the other hand, some users see inverter welding machines as the solution to all their problems. They are amazed at all the functions these machines provide with just the pushing of a button. As a matter of fact, the newer models offer some functionality that can enhance the results to the point that an average operator may produce weld beams similar to those made by highly skilled workers.

At some point, welding equipment manufacturers tried to build a machine that would combine the advantages of each technology, both transformers, and inverters. They were trying to put together the best of two worlds, but they failed at it. The final product was both too complicated and too expensive. So, that leaves us today still looking for the perfect answer to our hot debate between inverter vs transformer welding machines.

Can we say that inverters are taking over the welding machines market nowadays? Well, look at this: from the entire Miller Welds current catalog (with hundreds of machines) only 4 are transformer ones. The tendency is clear, but still, there is some room for the good old transformers.

Everything you need to weld

More than 40 years of welding experience

We started in 1979 and now we are throughout the Americas with all what is related to welding.

What transformer welding machines are

Transformer welders are the traditional welding machine since their inception, a hundred years ago. They are considered the workhorse of the industry. These welding machines are usually heavy-duty, require mains electricity, and are widely used for heavy industrial welding applications or as stationary workhorses in welding shops.

The transformer’s technology takes a high-voltage, low-amperage current and reverses it into a low-voltage, high-amperage current. This way, an AC high voltage input (Like 110V, 220V, 380V, etc.) with a low amperage current (Like 30A, 40A, 60A, etc.) becomes 17V-45V at 200A-600A.

A little bit of history

Welding has been an industrial activity since the 1800s. In the beginning, only was possible to weld using gas. In the 1920s the first transformer welding machines were invented, when they discovered that transformers could also be used to produce a welding arc. From that moment until now, transformer welding machines have undergone a series of improvements to control the arc. This research and development brought also the need to create coated arc welding electrodes, that we still use today.

World War I was a tipping point for welding, for the need to produce ships and tanks, built almost entirely out of metals. Before then, putting together two sheets of metal was only possible through rivets and gas welding.

In the period between 1920-1930, transformer welding machines became popular due to the possibility of power in more and more places. As an example, they built the Empire Building, whose construction began in 1930, using only transformer welding machines. Not too shabby, right?

The years after World War II brought a lot of development into welding, because of the need for manufacturing and building. Surprisingly enough, for some 50 years, the technology used for welding didn’t change. This tells us about the durability and reliability of transformer welding machines throughout the years.

What inverter welding machines are

The other corner of this ring shows up the up-and-coming inverter welding machine. Inverters are welding machines that use modern technology to improve efficiency. In fact, most of them also have a transformer, but they use solid-state electronic parts to reduce their size and increase their power.

Inverter welding machines work by means of increasing the power input frequency from 50Hz to some point between 20,000 – 100,000Hz. They use electronic switches, which turn the power on and off up to 1 million times a second. This higher frequency energizes the core 100,000 times a second instead of 60 times a second, as usual in transformer units, allowing the inverter to increase the AC frequency significantly.

Usually, they include digital functions (by means of hardware and software) to control arc stability, shielding gas flow, frequency, starting and ending amperage, arc cone width, AC balance, bead profile, wire burn-back, inductance, as well as other welding variables.

Inverters are compact, lightweight, versatile, and efficient welding machines. They usually can handle a bunch of welding processes, helped by electronic components and software. They also can weld a range of materials, including stainless steel and carbon steel.

Another little bit of history

The inverters were brought to life due to the boom in electronics and software-related applications so common in the 1980s. That decade was kind of experimental for inverter welding machines, which started to be heavily commercialized in the 1990s.

Nevertheless, its beginning was not so easy. The inverter ones gave to manufacturers a lot of trouble at the beginning when some of them burned out in the middle of a job. It was hard to delete that memory and grow trust in inverters. Also, the first models were very expensive, due to the electronic components, and specialized manufacturing. For many years the landscape was dark for inverter welding machines. That story started to turn around in the 2000s.

From those years on manufacturers have found ways to keep improving the inverter welding machines. By means of added solid-state electronic parts and software they have increased the number of functions the devices are capable of. Some advancements regarding safety (VDR) and protection against the environment have been added to produce more rugged equipment, able to thrive in the worst work conditions.

What is the IGBT

We cannot talk about the basics of inverter welding machines and forget about the IGBT. This acronym stands for Insulated Gate Bipolar Transistors. They are a semiconductor-based, three-terminal technology used for high-efficiency electrical power switching. They are used to synthesize complex waveforms

IGBTs were not present at the beginning of the production of inverter welding machines. At that time they used MOSFET systems, but the latter proved to be not efficient enough to handle high voltages, producing early failure in many units. IGBTs have come to stay and they are present today not only in welding equipment but also in all kinds of electronic devices.

Inverter vs transformer: What about equipment life?

If you have over 100 years of doing the same thing, it is safe to say that you are an expert on that. Well, welding manufacturers have been building transformer welding machines for more than 100 years. During all this time transformer welding machines have been gone through a series of upgrades and improvements that have given as a result a very robust and long-lasting equipment.

Many transformer welding machines last for several decades. In some manufacturing plants can be found some 50 years old units, still in use. If you are thinking about leaving a piece of equipment to the next generation, a transformer welding machine could be the one.

Of course, since transformer welding machines have been out there for 100 years and inverter welding machines only for 30, it is kind of unfair the comparison. 

Something that still is against the durability of the inverter welding machines is the environmental conditions found outdoors. Some factors are humidity, dust, etc. might affect the internal components of the machine, increasing the probability of failure and reducing their life expectancy.

In the last years, a longer equipment life has been seen in inverter welding machines. Still, only time will tell if they would be able to beat the rough and long-lasting transformer welding machines. Yes, transformer ones win this point.

Inverter vs transformer: What about the reliability

If you ask a person what feature they value in their car, reliability is the most given answer. Regarding the welding machine is no different.

Now, reliability has a stronger importance depending on the use you plan to give to that welding machine. Are you a hobbyist who eventually would like to weld something? Or are you the owner of a metal workshop that is welding day in and day out? As you can see, the reliability you need from the equipment varies.

In general terms, we want to be able to use the equipment whenever we need it. So, reliability is an important factor, hands down. In this area, transformer welding machines have been out there for 100 years. They have been upgraded and enhanced by the manufacturers, to the product we have today. Many workshops have transformer welding machines that weld day in and day out, without stopping, and basic maintenance. That could be the meaning of reliability.

Since inverter welding machines have been in the market for only 30 years, we can say that still is a product in development. We have seen an increase in the reliability of this equipment over the years. But is too soon to say that they beat the transformers at this point.

Transformer welding machines take it all in this aspect.

Inverter vs transformer: What about multiple functions?

There is a clear winner here: inverter welding machines. Transformer welder machines provide essential useful functions via mechanical methods, but inverter welding machines outnumber them due to the electronic components and software they have.

In a basic inverter welding machine, you can have several welding processes available. Just as an example, an AC TIG inverter welding machine can output different waveforms like triangular, square, and soft waves, while transformer ones are limited to a simple sine wave. Another possibility in inverters is the ability to perform pulsed TIG, ideal when welding thin metal.

Talking about the processes, in a pretty small, actually portable,  inverter welding machine, you can have AC/DC TIG, MMA, MIG, and Flux-cored available with dual voltage inputs. A big-time swiss army knife, right?

I told you, inverters run this section.

Inverter vs transformer: What about costs?

Costs are never easy to define. When calculating the costs in our inverter vs transformer challenge we need to break it down into at least 3 aspects:

  1. The cost of acquiring the equipment
  2. The costs related to the use of the equipment
  3. The costs related to maintenance, repairs, and downtime

The cost of acquiring the equipment is a gap that has been closing for the last 20 years. As we stated before when newly launched the inverter welding machines were very expensive. Over time the electronic components used for their fabrication were lowering their prices, which gave as a result cheaper inverter equipment with more functions. As of now is safe to say that the cost to acquire any of the systems is almost the same.

The costs related to the use of the equipment point out to power consumption. Since inverter welding machines are more efficient most experts coincide in a power saving of around 10-20%. When we are talking about industrial manufacturing, this apparently small percentage may represent thousands of dollars.

The maintenance, repairs, and downtime are debatable costs. On one hand, is a fact that transformer welding machines are almost maintenance-free, and despite that, they can last a long time, under rugged workplaces, while inverter welding machines are prone to failure if they face harsh conditions.

It is also true that inverter welding machines use expensive electronic components that, when fail, lead to costly repairs, due to the spare parts and specialized labor. Nevertheless, if the inverter welding machine is handled properly and is kept in more ideal conditions, the chances of the equipment needing repair are very low.

Taking into account all these 3 points, we see clearly that inverter welding machines win on the costs side.

Inverter vs transformer: Other differences

So far we have considered 4 differences in this case of inverter vs transformer welding machines. But there are more points to make. Let’s review now how these 2 systems differ from each other regarding performance, welding environment, and efficiency.

Inverter vs transformer: Performance

The performance of a welding machine relates to how good carry on its job. The main point of a welding machine is to keep a stable arc. Throughout the years the development of transformer welding machines has reached a point where we can say that they provide a reasonably stable arc. Nonetheless, they cannot modify the arc in real-time, so they are prone to arc voltage fluctuations, arc blow, and so on.

This situation is even harder if the welding machine is connected to “dirty” or unstable power. Sometimes, when welding outdoors you might need to connect your welding machine to a generator. In that case, the output voltage may fluctuate. Traditionally, transformer welding machines work fine in that environment.

Most recent inverters include power factor correction or PFC, a function that automatically compensates for voltage surges and provides adequate voltage to the inverter. Generator-friendly inverter welding machines also include high-voltage capacitors to prevent damage from an unstable current.

In this same aspect, inverter welding machines count on the IGBT which contains an internal microcontroller that controls (well, that is exactly what a microcontroller does) over the arc in real-time. This way the arc is provided with a reliable constant voltage, which, by the way, allows the machine to perform more functions.

The post-welding operation is also taken into account here. Many professionals are of the opinion that when using inverter welding machines the clean-up is less, the penetration is more uniform, and the bead profile is more consistent.

Again, in this point, inverter welding machines take the trophy.

Inverter vs transformer: Welding environment

When we are talking about putting some equipment to the test in the environment immediately think of the hardest conditions possible, like how automotive makers test their cars in the desert and other very difficult terrains.

For decades transformer welding machines have been out there supporting the worst conditions, and they have performed well. We honestly cannot say the same thing for inverter welding machines, which are more vulnerable to humidity, wind, dust, and mishandling from the operators.

Let’s give the medal here to transformer welding machines. They deserve it.

Inverter vs transformer: Efficiency

At this point, I wouldn’t put my money on the transformer welding machines. Let me explain why.

The inverter welding machines use on average half the amperes that transformers need to get the same amount of volts. Just by stating this, we can see a winner here.

Nowadays most inverter welding machines are capable of running both AC/DC power and dual voltage, meaning that you can use both 110V/220V power supply. This allows us to use them in houses, where in many countries the current is only 110V.

Also, the duty cycle must be considered when talking about efficiency. Most inverter welding machines rated a maximum output of 60% duty cycle, while this value is limited to 20-30% in the case of transformer welding machines.

The heat generated by the operation plays a role here. While it is true that inverter machines get heated more quickly than transformer welding machines, they have internal components to dissipate that heat, and since their components are smaller, they cool faster. So, inverters are ready to work again in a short period of time.

If you followed my advice above, now you are collecting your money.

Ask the experts

Our experts are ready to help you

We have experts in welding, cutting, industrial finishing and automation. Take advantage of our experience.

So, which one is better, the inverter or the transformer?

There is not a firm and direct answer to this question because as you have read, each system has pros and cons. So, the real answer can only be provided by you, based on what you do.

There is not a firm and direct answer to this question because as you have read, each system has pros and cons. So, the real answer can only be provided by you, based on what you do. The following table can help you to decide, according to your circumstances.

Let us help you to decide

Buying a welding machine can be a long-lasting investment. You don’t want to get it wrong. If you want, we can help you to decide, based on your own situation. Contact us and you will get that shiny welding machine very soon.

Request more information

Leave a Reply

The authors

Codinter Editorial Team

Codinter Editorial Team

The Codinter Editorial Team is composed of a diverse and multinational group of specialists, researchers, and writers, equipped with field experiences throughout decades of developing solutions with technology for industrial purposes.

Spread the knowledge


Stay with us

We want to share what we have learned from the decades of experience we have with products and services for the industry in America. All this educational content is now at your disposal.