There are two main types of welders: inverter and transformer. Understanding the differences between them will help you select the right equipment for your welding projects.

Inverter welders are known for their efficiency and lightweight design, which make them highly portable and suitable for various applications. On the other hand, transformer welders are known for their long-term reliability and robust construction, ideal for enduring harsh conditions and heavy-duty use.

When it comes to inverters vs transformers, there are arguments for both, but ultimately, your choice will depend on the specific requirements of your welding tasks and the working environment.

What Is an Inverter Welder?

An inverter welder is a welding machine that uses solid-state electric components and sophisticated silicon-based technology to convert power efficiently. These units are light and portable and produce a stable arc that allows for precision and control.

Inverter welders incorporate high-tech electronic components to switch electrical power from alternating current (AC) to direct current (DC), catering effectively to your welding demands. The hardware and technology in these machines allow for a range of digital controls, including inductance, wire burnback, hot start, crater fill, pre- and post-gas flows, AC balance and frequency, arc width and stability, and more.

How Does an Inverter Welder Work?

An inverter welder converts AC power into a lower usable output voltage through electronic rectification. This conversion process happens through high-speed switching by electronic components.

Here’s a step-by-step process of how it happens:

1. First, the inverter welder takes in the standard 240V AC power from the mains supply it’s plugged into. This is typically at a frequency of 50-60Hz.
2. The incoming AC power is then converted into 20V DC power. This conversion is necessary because the inverter technology operates on DC.
3. The DC power is then passed through a series of electronic switches, typically made up of IGBTs (Insulated Gate Bipolar Transistors) or MOSFETs (Metal Oxide Semiconductor Field-Effect Transistors). These switches are responsible for regulating and controlling the voltage and current according to the welding process requirements.
4. The regulated DC is then ‘inverted’– it’s switched on and off at a very high frequency, often between 20,000 to 100,000Hz. This high-frequency switching is the core of inverter technology.
5. The high-frequency DC is then fed through a much smaller transformer than what’s in a traditional transformer welder. The higher frequency allows the transformer to be more efficient and much smaller in size.
6. Finally, the transformed high-frequency current is rectified back to a controlled DC output, which is used for welding. The output power can be finely tuned to suit a variety of welding tasks.

Here’s a simplified breakdown of how it works:

• Input AC Power → Rectifier → DC Power
• DC Power → High-Speed Switching → Modified DC or AC Output

This process allows a substantial amount of power to be contained in a much smaller core and, therefore, a more compact package, making your inverter welder portable and light.

What Is IGBT Technology?

An IGBT is a three-layer semiconductor device used in electronics, including inverter welders. It combines the characteristics of both bipolar junction transistors (BJTs) and MOSFETs to provide an efficient means of controlling electrical power.

Apart from inverter welders, IGBTs are widely used in electric cars, trains, refrigerators, air conditioners, and variable-frequency drives in industrial control systems. These days, IGBTs are much more common and preferred over MOSFET systems as they offer several advantages over them.

They’re more thermally stable than MOSFETs at high currents, making them more reliable for high-power applications. Plus, many IGBTs come with built-in protection features like over-current, short-circuit, and over-temperature protection, enhancing their durability and safety in various applications.

Pros & Cons of Inverter Welders

Pros	Cons
Lightweight & portable Energy efficiency Improved quality Multi-process capable Better arc stability Less maintenance  Reduced noise Digital functions  Electrical consumptions	Cost  Sensitivity to power fluctuations Repair complexity

Pros

• Lightweight and portable
  Inverter welders are significantly lighter and more compact than transformer welders, making them easy to transport and suitable for on-site work.
• Energy efficiency
  They are more energy-efficient, as the inverter technology can convert power with minimal loss, reducing electricity costs.
• Improved quality
  Inverter welders provide better control over the welding arc, with smoother starts and more precise heat control. This improves weld quality, especially on thin materials or detailed work.
• Multi-process capable
  Inverter welders can perform various types of welding (like TIG, MIG, and stick) in one machine and work on different materials.
• Better arc stability
  The high switching frequency of IGBT technology in inverter welders allows for a more stable arc and better performance at lower currents.
• Less maintenance
  Generally, they require less maintenance than transformer welders due to fewer moving parts and solid-state electronics.
• Reduced noise
  Inverter welders often operate more quietly than their transformer counterparts.
• Digital functions
  Get a range of functions over your MIG, TIG or stick welds with added controls.
• Electrical consumption
  Consume less electricity and can often run on lower voltage inputs, making them cost-effective over time.

Cons

• Cost
  Inverter welders are typically more expensive upfront than traditional transformer welders, though this can be offset by their lower running costs, energy efficiency and versatility.
• Sensitivity to power fluctuations
  They can be more sensitive to power supply fluctuations and may require a stable power source for optimal performance.
• Repair complexity
  TIf an inverter welder breaks down, repairing it can be more complex, often requiring specialised knowledge and parts.

What Is a Transformer Welder?

A transformer welder is a type of welding machine that uses a transformer to convert the high voltage and low current electricity from the mains power supply into a lower voltage and higher current form suitable for welding. These welders are based on more traditional technology compared to inverter-based welders and are considered the ‘conventional’ way to weld.

How Does a Transformer Welder Work?

A transformer welder uses a ‘step down’ transformer to convert the high-voltage, low-current power from the mains supply to a lower voltage but higher current. This is essential because welding requires a high current to generate enough heat to melt the metal.

Depending on where you are, the standard mains electricity supply is 220-240 volts or 110-120 volts, with a current limit determined by the circuit breaker (usually between 10 to 20 amps). The transformer then outputs a reduced voltage of around 20-30 volts with a current of 200-600 amps.

This conversion of power is done by the internal ‘core’. Inside the welder is a transformer, which consists of two sets of coils or windings (primary and secondary) wrapped around a magnetic core. When the AC power flows through the primary winding, it creates a magnetic field.

As the magnetic field fluctuates with the AC power, it starts a current in the secondary winding of the transformer. This process of electromagnetic induction transfers energy from the primary to the secondary coil.

The output from the secondary winding is used for welding. Some transformer welders have a rectifier that converts AC to DC, offering both AC and DC welding capabilities.

The choice between AC and DC output depends on the welding application and the materials being welded. However, for the most part, transformer welders are AC-only outputs.

In simpler transformer welders, heat control is achieved by selecting different taps on the transformer, which changes the voltage and, thus, the arc’s heat. More advanced models might have additional controls for fine-tuning the output.

Pros & Cons of Transformer Welders

Pros	Cons
Durability Ease of repair Less sensitive  Time-tested	Size & weight  Lower energy efficiency  Limited control and versatility Noisy  Slow response time Lower duty cycle Less stable arc

Pros

• Durability
  Transformer welders are known for their robust construction. They tend to have a longer lifespan due to their simple design and fewer sensitive electronic components compared to inverter welders.
• Ease of repair
  Due to their simpler technology, transformer welders are generally easier and less expensive to repair. The components are more straightforward and often more accessible.
• Less sensitive to power fluctuations
  Transformer welders are generally more tolerant of power supply fluctuations and can operate in environments with less stable electrical supplies.
• Time-tested
  Transformers have been in use for over a century.

Cons

• Size and weight
  Transformer welders are typically larger and heavier than inverter welders. This can be a significant disadvantage in terms of portability and space requirements.
• Lower energy efficiency
  These welders are less energy efficient. They consume more power for the same welding output compared to inverter welders, leading to higher operational costs.
• Limited control and versatility
  Transformer welders offer fewer options for fine-tuning the welding parameters. This can limit their versatility, especially for welding thin materials or applications requiring precision.
• Noise
  They can be noisier than inverter welders, which might be a concern in certain working environments.
• Slow response time
  The response time to changes in welding conditions can be slower in transformer welders, which might affect welding quality in dynamic situations.
• Lower duty cycle
  Due to lower efficiency, transformer welders can generate more heat, which might require additional cooling measures and limit their duty cycle.
• Less stable arc
  Transformers have a less stable arc compared to inverters.

Inverter vs Transformer Welders

When choosing a welding machine, you’ll notice that inverter and transformer welders offer distinct differences in components, design, and function. Each type brings its own advantages to different welding applications.

	Inverters	Transformers
Weight	Low	High
Size	Compact	Huge
Efficiency	High	Low
Duty cycle	Longer	Shorter
Generator support	Compatible	Optimal
Advanced digital arc control	Yes	No
Current output	AC and DC	AC (and DC with rectifier)
Multi-process	Yes	No
Arc stability	More	Less
Cost	Less $	More $
Technology age	Newer (and improving)	Old
Lifespan	Shorter	Longer

Component Comparison

Inverter welder technology uses advanced electronics to control the power supply more efficiently. These welders convert AC power into a lower usable output voltage through electronic circuitry.

In contrast, transformer welders rely on traditional transformer technology with fewer electronic parts, often resulting in a simpler but bulkier design. The limited electronics in transformers means they tend to have a much longer life span, as there aren’t as many parts that need repair over time.

However, as well as the larger size of the transformer machine, the technology in them means they’re nowhere near as versatile or have anywhere near the amount of customisation compared to an inverter welder.

Portability & Weight

Inverter welders generally have a much more compact design, making them lighter and more portable than transformer welding machines. The weight difference is primarily due to the inverter’s use of smaller transformers and electronic parts, whereas transformer welders contain larger, heavier transformers necessary for their operation.

Because of this, transformer machines are best used in situations where they can remain stationary, while inverters are much easier to take around a shed or garage or between job sites.

Arc Stability & Control

The arc stability and control you experience with an inverter welder are superior due to its high-frequency operation and responsive power control. The IGBTs in inverted welders are controlled by an internal microcontroller, allowing for control of the arc while welding.

This results in a more reliable constant voltage, a more stable arc, the ability to perform a wider range of functions and an overall smoother welding experience with less spatter.

With transformer welders, the arc stability is good, but it can be less refined than the more modern inverter technology. Transformer-based machines are susceptible to arc voltage fluctuations, arc blow, and other related issues since they can’t adjust the arc while welding.

Welding Process

Only inverter welders can do MIG, TIG, and stick welding in one multi-process machine. They provide better performance across all three methods due to their advanced control features.

On the other hand, transformer machines are only capable of a single welding process, as the windings in the machine determine its function.

The Key Differences in Performance

When weighing up inverter vs transformer welders, there’s a distinct difference in performance across the board.

Efficiency & Power Supply Management

Inverter welders are known for their superior energy efficiency. They rapidly convert a 240V AC supply to a 20V DC power supply to maintain a consistent voltage output, leading to a much lower energy consumption rate than a transformer. You can also get the same amount of amperage output with half the amount of input power.

For example, the WORKSHOP 270, a transformer machine, has a maximum output amperage of 250A and requires a 32A plug. In comparison, the RAZOR COMPACT 250, an inverter machine, has a maximum output of 250A and only requires a 15A plug.

The inverter machine has just as much output power with half the input.

Reliability & Repair

Transformer welders are often considered more reliable over the long term, especially under harsh conditions. This opinion is generally held because transformer machines have been used for decades, with many old transformers running for that entire time.

They have simpler internal components that require less maintenance, so they’re not prone to breaking down or needing repair.

That’s not to say inverter machines aren’t reliable. These days, inverter machines are often just as reliable, thanks to significant technological improvements since their development.

Most high-quality inverter welding machines also have extended warranty periods to support this fact. UNIMIG’s RAZOR welders come with 3-year or 5-year warranties, with almost every machine having a lifespan longer than that.  

Weld Quality & Versatility

The quality of your weld and the versatility of the equipment are important factors to consider.

Inverter welders allow for precise control over the welding parameters, providing a range of settings to adapt to different materials and thicknesses. These extra settings and features allow it to produce superior welds and work on a much wider range of applications.

Inverter welders also offer advanced features such as pulsing, pre- and post-gas adjustments, and hot start and arc force control, making them more user-friendly and suitable for a wider range of welding techniques.

Overall, the quality of welds produced by inverter welders, combined with their versatility and advanced features, make them a valuable tool for professional welders and DIY enthusiasts alike.

Duty Cycle

A machine’s duty cycle determines how long you can weld before needing to let the machine cool. Inverter welders typically offer a better duty cycle than transformers, allowing you to weld longer without overheating.

The core inside a transformer machine is quite large, and it generates heat through electrical resistance. The problem is that this heat doesn’t dissipate very fast. In comparison, while the smaller transformer inside an inverter machine still generates heat through electrical resistance, its smaller size allows the heat to disperse.

As well as a smaller transformer, the other electrical components (like the PCB boards) in the inverter welders are also small. Though they heat up quickly, they’re easy to cool. These machines have fan systems and airflow tunnels to help reduce the internal temperature of these parts, keeping the overall internal temperature down.

The longer duty cycles of an inverter welder can be especially valuable if you’re operating under time constraints and need to maximise your output. Keep in mind that specific duty cycles can vary between different machines and the type of welding being done.

Generator Compatibility

Their electrical parts make them more versatile, but they also make inverter welders sensitive to power quality. They require stable power, as generators with fluctuating voltage (known as ‘dirty’ power) can damage their sensitive electronics. To avoid this, high-quality generators with a total harmonic distortion (THD) rating below 6% should be used.

Many inverter welders also have protective features like Power Factor Correction (PFC) and high-voltage capacitors that make them generator-friendly and more adaptable to varying power conditions.

Their simpler design makes transformer welders less sensitive to power fluctuations. They can operate effectively with a broader range of generators, even those not specifically designed for low THD output.

If you’re looking for a generator to suit your machine, check out our blog on choosing the best generator here.

Cost Comparisons

There are differences in price when deciding between a transformer or an inverter welder, like the initial cost, which is often influenced by technological advancements.

Initially, inverter welders were quite expensive, and while that is still true in some cases, the price of a new inverter welder has dropped significantly. Thanks to the advancements in IGBT technology, inverter welders are now more affordable, often less expensive than a transformer-based welder, unless you’re buying a second-hand one.

This price reduction has made welding equipment more accessible and opened welding up to a broader range of users, from professionals to hobbyists. In response to the rising popularity of inverter welders, manufacturers are gradually phasing out transformer welders.

Many brands have stopped producing transformer welders for the commercial market, focusing instead on the more in-demand, cost-effective inverter models.

It’s also important to remember that prices can vary based on factors like brand reputation and build quality. Even within the inverter welder category, these factors can influence the price, with premium brands and higher-quality models commanding a higher cost.

When choosing a welder, consider the type of work you’ll be doing, the power sources available, and the long-term cost implications. Inverter welders are generally better for a wide range of applications and environments, offering modern features and energy efficiency.

Ultimately, deciding between an inverter and a transformer welder is a balance of functionality, cost, and personal or professional requirements. By understanding these factors, you can make an informed choice that best suits your welding needs.