MOS DC inverter TIG welder IGBT Gas-shielded welding machine MOS inverter air plasma cutting machine MOS DC inverter manual arc welding machine

Inverter Welder 
MOS DC inverter TIG welder 
MOS inverter welder machine 
IGBT Gas-shielded welding machine
AC/DC TIG inverter welder  
MOS inverter air plasma cutting machine 
MOS DC inverter TIG welding machine
MOS DC inverter manual arc welder
MOS DC inverter manual arc welding machine

IGBT gas shielded welder component & structure:

MOS inverter arc air plasma cutter component

SPECIFICATIONS

 inverter circuit,high frequency arc starting;

-compact,portable,highly effective,low power consumption;-automatic compensation for voltage fuctuation,can work against input voltage fuctuation(V±15%);

-small splashing,great penetration,easy and simple to operate and aesth appearance of weld seam;

-over-voltage protection,undervoltage protection,over current protection,over load protection. inverter welder parts

ADVANTAGE

1,suitable for welding metal plate with thickness above 0.8mm.

2,low cost but with high efficiency. 

3,both output current and voltage could be adjustable to satisfy different welding requirement.

4,small splashing,great penetration.

5,two options of wire feeder:built-in or separated. inverter welder parts 

welding machine board ARC IGBT PCB Single board IGBTdc inverter welder AC220V input r welding control board 3 in 1










What Is an Inverter Welder?

Inverter welders are basically power inverters; they convert 120-volt AC power to DC electricity to power welding torches. Because you can plug one into a conventional 120-volt receptacle, it's more convenient to use than a stand-alone DC-current generator. The DC power passes through a transformer to step it up to the level needed for welding.

Frequency is Key
The on/off action of switches called IGBTs are the secret to increasing frequency of the primary power that reaches the welder’s transformer. This action simulates the increase and decrease of a magnetic field, similar to that of electrical alternating current but at a much higher frequency.

Size
Inverter welders are much smaller than conventional welding units, making them portable, as they may be transported in a carrier instead of being rolled to jobs on a special dolly. Because of their small size, they are also ideal for do-it-yourselfers and for use in tight areas that cannot accommodate portable generators that are sometimes required to run traditional welders.

Efficiency
Because they run on household current, inverter welders use less electricity, making them more economical. Their design also makes welding more efficient thanks to a smooth arc, small spatter and stable welding current.

Inverter Tig Welder /IGBT Inverter/ DC to AC Inverter Tig Welding / Welder Welding

An inverter welder is a type of welding power supply capable of providing a high current for welding. The welder uses a series of rectifiers and solid-state switches to convert 60 Hz alternating current (AC) input power into direct current (DC) output power. The amount of output current and voltage available during the welding process is controlled by computer software. An inverter welder weighs considerably less while at the same time consumes less electricity than a comparable traditional welding power supply.

A traditional welding power supply uses a large, iron-core transformer to convert low amperage, high voltage AC into high amperage, low voltage AC. A rectifier is then used to convert the AC into DC for use in the welding process. The transformer in this type of power supply typically needs to be quite large to work correctly.

An inverter welder first uses a rectifier to convert the incoming AC into DC. This current is the switched on and off very quickly, creating a pulsed, high frequency direct current. Typical frequencies range from 10,000 to 20,000 Hz, although frequencies as high as 100,000 Hz are possible. The high-frequency, low-amperage current is fed into a transformer where it is changed into high amperage DC, before being rectified again.


These have several advantages when compared to a traditional welding power supply. Both require a transformer to convert incoming current to suitable welding current, though with an inverter welder, this can be done more efficiently at higher frequencies; as a result, the inverter is able to use a much smaller transformer. The result is a substantial reduction in size and weight. Power consumption also decreases as the more efficient transformer loses less energy to heat. It is possible to run an these welders on typical 115 VAC household current due to lower input voltage requirements.

Due to the higher frequency of the output current, an inverter welder produces a smother arc when welding. Computer software constantly monitors and adjusts current and voltage during the welding process, resulting in a consistent arc. As a result, welding supplies such as electrodes, welding wire and shielding gas typically last longer than when using a traditional welding power supply. Adjustments to current and voltage can be made to accommodate differences in material composition and thickness, giving the welder tighter control over the welding process. It is possible to use an inverter welder to power all welding processes including Stick, Metal Inert Gas (MIG) and Tungsten Inert Gas (TIG).

The reduced size and weight of these welders make them popular choices for applications where a traditional welding power supply would be too bulky or consume too much power. They are commonly used in machinery maintenance facilities and automobile repair shops. Many welding and fabrication shops are replacing their traditional welding power supplies due to the potential cost and space savings afforded by inverter welders. Farmers, as well, are increasingly turning to portable, lightweight units to make on-site repairs.


What is MIG Welding?

Metal Inert Gas (MIG) welding, also sometimes called Gas Metal Arc Welding (GMAW) is a process that was developed in the 1940s for welding aluminum and other non-ferrous metals. MIG welding is an automatic or semi-automatic process in which a wire connected to a source of direct current acts as an electrode to join two pieces of metal as it is continuously passed through a welding gun. A flow of an inert gas, originally argon, is also passed through the welding gun at the same time as the wire electrode. This inert gas acts as a shield, keeping airborne contaminants away from the weld zone.

The primary advantage of MIG welding is that it allows metal to be welded much more quickly than traditional "stick welding" techniques. This makes it ideal for welding softer metals such as aluminum. When this method was first developed, the cost of the inert gas made the process too expensive for welding steel. Over the years, the process has evolved, however, and semi-inert gases such as carbon dioxide can now be used to provide the shielding function, which now makes MIG welding cost-effective for welding steel.

Besides providing the capability to weld non-ferrous metals, MIG welding has other advantages:

It produces long, continuous welds much faster than traditional welding methods.
Since the shielding gas protects the welding arc, this type of welding produces a clean weld with very little splatter.
It can be used with a wide variety of metals and alloys.
The primary disadvantages of MIG welding include the following:

The equipment is quite complex, as MIG welding requires a source of direct current, a constant source and flow of gas, as well as the continuously moving wire electrode. Plus, electrodes are available in a wide range of sizes and are made from a number of metal types to match the welding application.
The actual technique used is different from traditional welding practices, so there is learning curve associated with MIG welding, even for experienced welders. For example, MIG welders may need to push the welding puddle away from them and along the seam.
The necessity for the inert gas shield means that MIG welding cannot be used in an open area where the wind would blow away the gas shield, unless other precautions are taken to prevent this.
Since its development in the middle of the 20th century, MIG welding has become commonplace in many manufacturing operations. For example, it is commonly used in the automobile industry because of its ability to produce clean welds, and the fact that it welds metals quickly.



Difference Between AC & DC Stick Welding

Stick welding refers to the common welding system that uses an electrode designed to be burnt away as it channels electricity. As the electrode burns, its coating produces flux gases to protect the weld from oxygen; the welder replaces electrodes as needed throughout the project. Stick welding is an easy type of welding to learn and practice and is used for iron and steel-based metals. AC and DC current are the two stick welding power options.

AC
AC stands for alternating current, the type of current found in house outlets. Alternating current cycles produces waves of electrical current that are balanced out by troughs and peaks. AC current became popular because it is safer for many types of appliances. The reference to hertz in electricity comes from the AC frequency pattern.

Welding Effects
While AC current is common for home appliances, is not used as often for professional stick welding. One of the main problems with AC current is the constant cycling of electricity, which creates varying waves of electricity when the arc has connected. This leads to potential outages and sticking problem, and may create more splatter. However, for certain alloys like aluminum or magnetized metals, the AC current may be more efficient.

DC
DC electricity is direct current, or a steady state form of electricity that forms one primary flow of electrons. This type of electricity does not reverse its flow to create the wave pattern seen in AC current. DC power comes from independent sources of electricity with a streamlined focus on only one application, such as batteries.

Welding Effects
DC current is used more often in professional welding because it creates a smoother weld line without the cycling effects that AC creates. DC current is especially useful for iron and steel, the metals used most often with stick welding, and creates faster, more controlled welds on thin metals than AC current does.






What Is the Difference Between AC & DC Welding?

Welding is the joining of two or more metal parts by melting them together. This process is unlike soldering, which is simply attaching two metal surfaces together via a piece of molten metal. Because the melting points of most metals are so high, specialized welding equipment uses the heat from an electric current to weld metal together.

Welding Arc, Filler Metal and Shielding the Weld
There are three main aspects to the welding process: the welding arc, filler metal and shielding the weld. A welding arc is a continuous spark that is generated by a welding machine and is used to heat the metal by several thousand degrees Fahrenheit. The spark is created by a circuit that passes from the machine through the metal being welded. Filler metal is additional metal added during the weld to strengthen the welded joint. A weld must be shielded from the surrounding air until it sets, as air can contaminate the weld. This shielding is accomplished by adding shielding gas to the process, provided by either a tank attached to the welding machine or a specially formulated filler metal that releases the gas as it melts.

Welding Arc Polarity
Like any electrical current moving through a circuit, a welding arc has polarity, with a positive and negative pole. Polarity has a significant effect on the strength of a weld. Electrode-positive, or reverse, polarity causes a deeper penetration of the weld then electrode-negative, or positive, polarity. However, electrode-negative polarity results in a faster deposition of the filler metal. When using direct current, the polarity is always constant. With alternating current, the polarity switches 120 times per second in a 60-hertz current.

Which is Better?
For all intents and purposes, DC welding is the preferred type of welding. Whether you are using electrode-positive (DC+) or electrode-negative (DC–) polarity, DC tends to produce a smoother weld than AC. Whereas DC delivers a constant and consistent current, the nature of AC means that it delivers a current that constantly swings back and forth from positive to negative. As the current swings back and forth, it must pass through a point at which there is zero current output. Although the current is only at this zero point for a fraction of a second, the disruption can be enough to disrupt the arc, causing it the fluctuate, flutter or extinguish completely.

When is AC Used?
Because AC welding is significantly inferior to DC welding, it is only used in rare circumstances. AC welding machines are most frequently used when there is no DC machine available. Derisively referred to as "buzz boxes," AC welding machines are considered entry-level technology. AC welding might also be used to fix arc blow problems. This phenomenon is marked by an arc that wanders or blows out the joint being welded. This usually happens when working with large-diameter electrodes at high current levels.



How to Make a TIG Welder Out of a Stick Welder

A stick welder is an electric arc welder that uses an electrical current to melt a consumable welding rod, or stick, into a weld. A Tungsten inert gas (TIG) welder uses a non-consumable rod shielded by argon gas to melt metal parts, usually sheet metal, together. Experienced welders agree the conversion can be done although you might not be thrilled with the results. Lincoln Electric manufactures a welder (the Invertec V155-S TIG and Stick Welder) that is basically a stick welder with a TIG accessory pack. Since most stick welders use alternating current (AC, the first thing you must do is convert that electrical source to direct current (DC).

Things You'll Need
Rectifier or DC stick welder
TIG torch with cable and hose
Flowmeter
Tank of argon gas


Instructions
Connect a rectifier to your AC stick welding box. You need DC for TIG welding and most stick welders provide an AC power source. You can, in fact, use any DC power source instead of using your box and a rectifier and you do not need a rectifier if you already have a DC stick welder.

Connect the power cable of a TIG torch to the negative electric terminal of the rectifier or your stick welding box. You can also clamp the welding rod holder, or "stinger," to the TIG torch power tab.

Connect the gas hose of the TIG torch to a flowmeter and connect the flowmeter to a tank of argon gas. Flowmeters are long gas hoses with a gas regulator valve.

Strike the TIG torch rod like a match to start the weld. Rock the torch element to one side and pull back to stop the weld. You will not have an amperage adjustment or an on-off switch.



Welding Electrode Classification

Welding is the process of joining materials together by melting the two pieces and adding a third melted material. Electrodes provide a current to the materials and are made of a variety of difference materials. Electrodes are manufactured for different purposes and welding types and are classified by a five-digit number like E7011-M. Each number and letter corresponds with a piece of information, including recommended welding position, tensile strength and penetration depth. The "E" in the classification stands for electrode.

Strength
The first two digits of an electrode classification indicate the strength of the electrode. This strength is measured in thousands of pounds per square inch (psi). For example, an electrode classified as E80xx has a tensile strength of 80,000 psi. This number also determines the yield strength or point of deformation for low alloy steel electrodes. Subtract 13,000 from the electrode tensile strength to determine the approximate minimum yield strength. For example, the E80xx electrode has yield strength of 63,000 psi.

Welding Position
The third digit of the electrode classification determines the appropriate welding positions. Welds are performed in four major positions: flat, horizontal, vertical and overhead. Exx1x electrodes can be welded using all four positions with the vertical position moving up. Exx2x electrodes use only flat and horizontal positioning. Exx4x electrodes may use all positions with the vertical position moving down.

Classification Type
The fourth digit represents the classification type. The classification type states the electrode's coating, penetration depth and required current type. Penetration depths range includes light, medium or deep. Current types include alternating current (AC), direct current electrode positive (DCEP) and direct current electrode negative (DCEN), though some electrodes use multiple types depending on the type of weld. For example, an Exxx7 electrode is coated with iron powder and iron oxide, has a penetration depth of medium and uses AC or DCEN power.

Additional Requirements
Certain electrode classifications include a suffix which identifies any additional requirements or information. Low alloy steel coated electrode requirements differ from the requirements of mild steel coated electrodes. Some common suffixes include M, which signifies military-grade electrodes, and G, which signifies that the electrode has no required chemistry.




Welding power supply

A welding power supply is a device that provides an electric current to perform welding. Welding usually requires high current (over 80 amperes) and it can need above 12,000 amperes in spot welding. Low current can also be used; welding two razor blades together at 5 amps with gas tungsten arc welding is a good example. A welding power supply can be as simple as a car battery and as sophisticated as a high-frequency inverter using IGBT technology, with computer control to assist in the welding process.

Classification
Welding machines are usually classified as constant current (CC) or constant voltage (CV); a constant current machine varies its output voltage to maintain a steady current while a constant voltage machine will fluctuate its output current to maintain a set voltage. Shielded metal arc welding and gas tungsten arc welding will use a constant current source and gas metal arc welding and flux-cored arc welding typically use constant voltage sources but constant current is also possible with a voltage sensing wire feeder.

The nature of the CV machine is required by gas metal arc welding and flux-cored arc welding because the welder is not able to control the arc length manually. If a welder attempted to use a CV machine to weld with shielded metal arc welding the small fluctuations in the arc distance would cause wide fluctuations in the machine's output. With a CC machine the welder can count on a fixed number of amps reaching the material to be welded regardless of the arc distance but too much distance will cause poor welding.

Power supply designs
The welding power supplies most commonly seen can be categorized within the following types:

Transformer
A transformer-style welding power supply converts the moderate voltage and moderate current electricity from the utility mains (typically 230 or 115 VAC) into a high current and low voltage supply, typically between 17 to 45 (open-circuit) volts and 55 to 590 amperes. A rectifier converts the AC into DC on more expensive machines.

This design typically allows the welder to select the output current by variously moving a primary winding closer or farther from a secondary winding, moving a magnetic shunt in and out of the core of the transformer, using a series saturating reactor with a variable saturating technique in series with the secondary current output, or by simply permitting the welder to select the output voltage from a set of taps on the transformer's secondary winding. These transformer style machines are typically the least expensive.

The trade off for the reduced expense is that pure transformer designs are often bulky and massive because they operate at the utility mains frequency of 50 or 60 Hz. Such low frequency transformers must have a high magnetizing inductance to avoid wasteful shunt currents. The transformer may also have significant leakage inductance for short circuit protection in the event of a welding rod becoming stuck to the workpiece. The leakage inductance may be variable so the operator can set the output current.

Generator and alternator
Welding power supplies may also use generators or alternators to convert mechanical energy into electrical energy. Modern designs are usually driven by an internal combustion engine but older machines may use an electric motor to drive an alternator or generator. In this configuration the utility power is converted first into mechanical energy then back into electrical energy to achieve the step-down effect similar to a transformer. Because the output of the generator can be direct current, or even a higher frequency ac current, these older machines can produce DC from AC without any need for rectifiers of any type, or can also be used for implementing formerly-used variations on so-called heliarc (most often now called TIG) welders, where the need for a higher frequency add-on module box is avoided by the alternator simply producing higher frequency ac current directly

Inverter
Since the advent of high-power semiconductors such as the insulated gate bipolar transistor (IGBT), it is now possible to build a switched-mode power supply capable of coping with the high loads of arc welding. These designs are known as inverter welding units. They generally first rectify the utility AC power to DC; then they switch (invert) the DC power into a stepdown transformer to produce the desired welding voltage or current. The switching frequency is typically 10 kHz or higher. Although the high switching frequency requires sophisticated components and circuits, it drastically reduces the bulk of the step down transformer, as the mass of magnetic components (transformers and inductors) that is required for achieving a given power level goes down rapidly as the operating (switching) frequency is increased. The inverter circuitry can also provide features such as power control and overload protection. The high frequency inverter-based welding machines are typically more efficient and provide better control of variable functional parameters than non-inverter welding machines.

The IGBTs in an inverter based machine are controlled by a microcontroller, so the electrical characteristics of the welding power can be changed by software in real time, even on a cycle by cycle basis, rather than making changes slowly over hundreds if not thousands of cycles. Typically, the controller software will implement features such as pulsing the welding current, providing variable ratios and current densities through a welding cycle, enabling swept or stepped variable frequencies, and providing timing as needed for implementing automatic spot-welding; all of these features would be prohibitively expensive to design into a transformer-based machine, but require only program memory space in a software-controlled inverter machine. Similarly, it is possible to add new features to a software-controlled inverter machine if needed, through a software update, rather than through having to buy a more modern welder.

Other types
Additional types of welders also exist, besides the types using transformers, motor/generator, and inverters. For example, laser welders also exist, and they require an entirely different type of welding power supply design that does not fall into any of the types of welding power supplies discussed previously. Likewise, spot welders require a different type of welding power supply, typically containing elaborate timing circuits and large capacitor banks that are not commonly found with any other types of welding power supplies.

Inverter-Based Welding Power Sources Help Solve Maintenance Problems, Decrease Downtime

If time means money, then an inverter-based welder and plasma cutter may provide the best return on investment for in-house plant maintenance and repair personnel, as well as the mechanical contractors that often perform this work. If you experience any of the following, inverter-based technology can likely reduce wasted time and lower cost:

• Difficulty moving heavy welders to the work site, such as downtime caused while waiting for a forklift, truck or crane to move the welder.
• Inability to bring a larger welder close to the job site while working in tight spaces.
• Difficulty finding useable primary power (e.g., only a 115 V outlet and you have a 230 V machine).
• Difficulty with primary power, such as voltage fluctuations, needing to add more welders but exceeding the capacity of the circuit, or facing additional assessed charges from the utility company for poor power factor (this bullet point applies to in-house personnel managing a fleet of welding equipment).
• Limited multiprocess welding capabilities, such as using one welder for Stick/TIG welding and another for MIG/flux cored welding.
• Problems with finding experienced welding personnel, or problems related to improper equipment set-up.

 Inverter-based welders and plasma cutters can solve all of these problems because their advanced technology dramatically lowers machine weight and size, provides primary power management capabilities not possible with conventional welding technology and delivers unbeatable arc performance. Further, today’s inverter technology makes machines easier to operate. Their enhanced arc starts and arc performance can turn an average welder into a good welder, leading to improved weld quality and fewer rejects.

While not the focus of this article, conventional welding technology remains a good choice for many maintenance and repair applications. These welders can withstand severe abuse, work in harsh conditions and continue to function well for decades. Further, their limited mobility becomes an asset in some situations. When a welder needs to be left on a job site overnight, users can be confident that a 4,000-lb. multiple operator unit will still be there in the morning. Fig. 1 (below) provides some brief guidelines for selecting a welder for maintenance.

	Conventional Welder	Inverter
Weight	·350+ lbs. for individual unit ·2,000 – 4,000 lbs. for multi-arc units	·10 – 120 lbs. for individual unit ·180 – 760 lbs. for multi-arc units
Input voltage range	208/230/460, etc. Requires manual relinking	115 – 230 or 230 – 575. Manual relinking not required
Single- or Three-phase	Fixed ability	Accepts both
Tolerance of voltage fluctuation	±10 % of primary	More tolerant¾See Auto-Line info
Power Factor	Poor – Good, depending on model	Excellent (up to .95; 1.0 is perfect). PFC inherent in design
Power Efficiency	Poor – Good, depending on age of unit	Excellent
Primary Current Draw	Traditionally higher	Traditionally lower
Multiple process arc quality	Fair – Good	Excellent
Enhanced arc control functions	Good	Good – Excellent
Durability	Excellent, generally more than 10 years	Good, generally up to 10 years
Reliability	Excellent	Fair – Excellent (varies by manufacturer)
Purchase price (cost per amp)	Generally lower	Generally higher

How Welders Work

All welders transform high voltage, low amperage primary power into the low voltage, high amperage power used for welding. The welder does this using a transformer, which is an iron core wrapped with hundreds turns of copper wire. Variables that determine the physical size of the transformer include the number of turns of wire, the cross-sectional area of the core, the voltage being applied and the frequency of the primary power.

The key variable—the one inverters address—is frequency. The equation that governs the design of a welder states that increasing the frequency of the primary power enables reducing size and mass of the transformer.

The secret of inverter technology is that it increases the frequency of the primary power reaching the transformer from 60 Hz up to 20,000 to 100,000 Hz. It does this through the on/off action of high power solid-state switches called IGBTs that turn on or off in as little as one millionth of a second. The on/off action simulates the building and collapsing of a magnetic field, which has a similar affect as AC power, but at a much higher frequency (see Fig. 2, a block diagram of an inverter, for more details).

By controlling power on the primary (or line side) of the transformer and boosting frequency, manufacturers of welding equipment now produce Stick/TIG inverters that weigh 10 to 50 lbs., all-in-one MIG welders that weigh less than 50 lbs. and multiple-process inverters (Stick/TIG/MIG/flux cored/gouging) that weigh about 80 lbs. and produce a 425-amp output. See Fig. 3 for a comparison of transformer size between a conventional welder and an inverter.

Fast ROI by Eliminating Wasted Time

In an average welding operation, labor accounts for 85 percent of the costs (see Fig. 4, welding cost chart). Measuring how much a repair costs includes time spent to bring the welder and the work together, welding equipment set-up time, material preparation time, arc-on time, welding clean-up time (grinding spatter and slag or, even worse, costly rework), time spent moving the welder between jobs and time spent returning the welder to the tool crib, job box or storage space.

One contractor performing scheduled maintenance on a power plant calculated time saved to justify upgrading to inverter technology. Previously, the contactor used an eight-arc multiple operator system that weighed 4,000 lbs. By shifting to a “rack” system that holds and powers six arcs from one primary connection¾and weighs only 712 lbs.¾the contractor reduced labor time by 87 percent. In addition, with the welder close to the work, operators could easily adjust welding parameters or change processes.

Today, a four-arc rack for TIG/Stick welding can weigh as little as 180 lbs.—rack included— measure a mere 50 in. high, fit in an elevator and feature wheels for extreme mobility. Rack systems also offer the flexibility of removing individual welders from the rack. The individual inverters are little larger than a briefcase or carry-on suitcase (size varies by output power), so one or two people can easily move a small inverter and bring it into a tight space.

Primary Power Flexibility

Saving time by bringing lightweight inverters to the work does no good if you can’t find anywhere to plug it in. Inverter provides location flexibility through two types of primary power management technology: automatic linking technology and Auto-Line™ technology, which is available on some inverters from Miller Electric Mfg. Co.

With automatic linking technology, the inverter senses the type of primary power applied, then automatically (but mechanically) links to the correct power: 230 or 460 V, single- or three-phase, 50 or 60 Hz.

The Auto-Line circuit eliminates mechanical linking and uses electrical linking instead. The circuit boosts primary power to a higher voltage, and this power then becomes the source voltage for the inverter. The following types of inverters are available with Auto-Line (amperages are given at maximum output):

• 180-amp all-in-one MIG welder that accepts 115 through 230 V, single-phase only, 50 or 60 Hz
• 150-amp Stick/DC TIG units that accept 115 through 230 V, single-phase only, 50 or 60 Hz
• 200-amp Stick/DC TIG and AC/DC TIG/Stick units that accept 120 through 460 V, single- or three-phase, 50 or 60 Hz
• 425-amp CC/CV multiple process welders that accept 208 V through 575 V, single- or three-phase, 50 or 60 Hz
• “Multi-MIG” welders that accept 208 V through 575 V, single- or three-phase, 50 or 60 Hz (these units are specifically for high-volume production welding, not maintenance and repair)
• 55- and 80-amp plasma cutters that accept 208 V through 575 V, single- or three-phase, 50 or 60 Hz

Note the emphasis on through. The primary power voltage can vary, but as long as it stays within the machine’s operating range, the power at the arc remains rock steady (see Fig. 5, Auto-Line circuit). Operators will never see a flicker, and the machine will operate continuously through conditions that cause other machines to shut down for self-protection or trip the circuit breaker. This benefit really pays off on sites with dirty power or when running off generator power. Note that to create a cost-efficient two-arc welding station in the field, some companies pair an engine-driven welding generator and use its generator power to run an inverter.

The availability of inverters with Auto-Line means that a person making welding repairs can move not just anywhere inside a plant, but can travel anywhere in the world without having to worry about finding available power.

More Power Per Pound, Less Current Draw

People encountering an inverter for the first time usually cannot believe that such a small machine provides so much welding output. For example, small Stick/TIG inverters weigh less than 14 lbs., but can have enough power to weld with a 1/8-in. Stick electrode. Even an inverter for carbon arc gouging with 3/8-in carbons at 600 amps weighs only about 120 lbs.

Inverters also provide outstanding power efficiency, which can lower utility bills, and they make good use of the primary power being supplied, which is known in the industry as good power factor. Good power factor lowers amperage draw, which may enable adding more welders to existing primary power. For example, one muffler manufacturer recently faced the dilemma of needing to increase production to meet demand, yet thought that it could not add to its fleet of 40+ arcs without making changes to incoming service—changes that may have cost up to $50,000.

Instead of adding more conventional 250-amp AC/DC TIG welders, which draw between 52 and 96 amps of primary power at rated output on 230 V primary, the company purchased 200-amp AC/DC TIG inverters, which draw less than 16 amps at rated output. The company added eight inverters, increased productivity and met demand without any changes to incoming service.

Mechanical contractors working in processing (petchem, paper, food) facilities and power plants also benefit from low primary power draw and primary power management. These job sites are often starved for power and may have generator power that fluctuates. An inverter’s low-amp draw means that a single generator can power more arcs and, as noted, features like Auto-Line enable an inverter to ride through voltage dips and spikes.

The Ultimate Welding Machine

By switching primary power at thousands of Hz and using advanced microprocessor control, an inverter can create optimum arc performance in any given welding mode. Thus, operators can weld at their best and not fight the arc, or they can select the welding process best suited for the job.

A brief review of inverter benefits in maintenance/repair applications include the following:

• Multiple process welding outputs. Models are available for Stick/DC TIG (for steel and stainless), DC TIG/Stick (these welders have more functions for controlling the TIG arc, such as pulsing and high frequency arc starts), AC/DC TIG/Stick (the AC output is necessary for welding aluminum) or a CC/CV output. The CC, or constant current output is used for Stick, DC TIG and gouging, while the CV output is used for MIG and flux cored welding. When a job requires both CC and CV processes, a CC/CV inverter means that there is one less machine to purchase or transport to the job site.
• Excellent arc starts. Weld flaws often occur during arc starts because the arc fails to establish itself quickly. Inverters typically provide more positive arc starting, which can help ensure a quality weld the first time, eliminating rework later. A single welding repair could cost hundreds or thousands of dollars, so eliminating a handful of weld flaws can pay for a new inverter.
• Dig control for Stick welding. Dig control prevents the electrode from sticking when the arc gets too short. This is helpful for an open-root pass or tight fit-up work and aids in arc initiation.
• Broad range of inductance control for MIG welding. This allows an operator to create a “softer” arc (more inductance) or “stiffer” arc. Add more inductance for better wet-out (especially on stainless) or to reduce spatter, which can save hours of post-weld grinding.
• Improved pulsed MIG or pulsed TIG output (ability to tailor the pulsed wave form). Depending on the application, pulsing can reduce heat input for less warping distortion or burn-through, improve bead aesthetics, reduce spatter, provide out-of-position puddle control and increase travel speed.
• Output frequency adjustment and extended balance control for AC TIG welding. These functions enable tailoring the weld bead profile to match the application to improve weld quality, minimize post-weld grinding and substantially increase travel speed.
• User-friendly controls. Functions such as last procedure recall remember preferences when changing the polarity, such as starting method and panel or remote control. To account for operator preferences, yet to keep operators out of trouble by making incorrect adjustments, some inverters have four-position controls simply labeled for “stiff” or “soft” arc characteristics with E6010 and E7018 Stick electrodes. Control panels are also color-coded by process, such as green for TIG, orange for Stick and blue for wire welding. Manufacturers also try to provide commonality among their equipment, so the control panel design on an inverter may resemble the control panel used on an engine-driven welding generator the operator used on a previous job.

In addition to user-friendly controls, manufacturers also address the need for user-friendly processes. The welding world generally acknowledges that wire welding (MIG or flux cored) is the easiest process to learn, with Stick being harder and TIG the most difficult (which is not to say Stick welding is easy!).

Nearly anyone with decent hand-eye coordination and the right attitude can become good at wire welding for general applications with a few hours of practice. However, wire welding for on-site repairs can be difficult. Even a small MIG welder that runs on 115 V power weighs 60 lbs., and the bottle of shielding gas often weighs more than the welder.

Miller addressed this situation by creating the world’s first entirely self-contained all-in-one MIG welder, the Millermatic® Passport™. This 45-lb. inverter (see Fig. 7) features a 12-oz. internal CO2 shielding gas bottle (actually a paint ball cylinder) that provides enough gas for 25 minutes of welding. For quick welding repair or light fabrication in the field, no other wire welder completes the job faster or easier.

If your job calls for bringing the welder to the work site, requires multiple process welding or you face challenges related to primary power management, then take a closer look at inverter technology. Saving 10 or 20 hours of time, a realistic goal on a single large job, means that a new inverter will pay for itself many times over within the two or three years typically allotted for capital investments. And

an inverter helps get a facility up and running in an emergency, it’s worth its weight in gold.

Fig. 7

Types of Arc Welder

Arc welding has been around for a long time, and there are now a number of distinct types of arc welder. This page discusses the pros, cons and typical characteristics of these different types of welder.

DC inverters

Unlike traditional arc welders, modern DC inverter arc welders are very small, light and portable. Even the cheap ones available from as little as £100 function well, though the more expensive ones (up to £500) will be much more robust and will normally last much longer.

Pros:

• Very efficient - they can run up to about 140 amps on a 13 amp 240V supply, and tend to have have good duty cycles (you can weld for longer on higher settings).
• Small, lightweight and very portable. Generally less than 10kg in weight.
• DC output results in easy arc starting
• Most inverters have features such as hot starting to improve the ease of starting, and a soft finish to reduce the crater at the end of a weld.
• All but the cheapest have 70V or 80V OCV (open circuit voltage)
• Most can be used for scratch start TIG. More expensive ones tend to have HF (high frequency) start functions for TIG welding.
• Pricier ones have features such as "arc force" which adjusts the voltage on the fly to cope with dirty plate.

Cons:

• Inverter machines are complex electronically, and repairs can be very expensive. The cheaper ones are sensitive to knocks and spikes in input voltage. The more expensive ones have more protection - some are designed to withstand being dropped from 0.5m.

Verdict:

DC inverters are the sensible buy for anyone new to arc welding. Even the cheapest ones tend to weld very nicely, the downside of the cheap ones being that cheap components that don't last very well.

AC/DC inverters

These are normally aimed at TIG welding, and would not be bought for arc welding alone, but they generally have arc welding settings.

Pros:

• Some rods are AC only. An AC/DC inverter can be used with these.
• AC is not susceptible to magnetism which can cause stray arcs on DC machines.
• The TIG welding capabilities.

Cons:

• Expense: For inverter welders the AC function takes a lot of electronics, so prices of half reasonable machines start at £1000.

Verdict:

Fantastic for ARC welding, but only buy one if you also need to TIG aluminium.

DC transformer welders

Transformer based arc welders are normally very heavy, and are aimed at TIG welding in a workshop rather than portability.

Pros:

• These are excellent quality welders - for ease of use they are only bettered by decent inverter welders.
• Duty cycles tend to be higher than modern inverter welders, so these machines are still used by fabrication companies when they need to do long runs of weld at very high amps.
• Can last for much longer than inverter based machines, and are easier and cheaper to repair if they do go wrong. Many are still in regular use after 30 years.
• The TIG welding capabilities.

Cons:

• Not Portable: A Syncrowave 300 weighs 330kg and is the size of a house.
• The machines with huge power requirements - the Syncrowave manual recommends a 110 amp 240V supply.
• The buzz from the enormous transformers and 2 foot diameter fans create a lot of noise.
• Parts available for the older ones is becoming sketchy.

Verdict:

Buy one secondhand if you want something that will last and have the space to keep it.

AC oil cooled welders

Pros:

• Very simple heavily built welders that should last for ever.
• Normally have both 50V and 80V settings. Smooth consistent arc while welding.
• Oil cooling results in an excellent duty cycle.
• It is possible to pick them up cheaply secondhand.

Cons:

• Not Portable: Oil cooled welders are very heavy, even small units can weigh in excess of 100kg.
• Starting the arc in AC is more difficult than with DC welders.
• Can't be used for TIG welding.

Verdict:

Old school equipment that you should never need to replace. Buy one second hand if you are old school, but bear in mind they take a little more skill to use.

AC air cooled welders

Often referred to as buzz boxes. A number of companies made reasonable quality air cooled AC welders in the past. The technology is now the reserve of DIY stores selling welders to people who don't know any better. They are the least usable of any type of arc welder.

Pros:

• Cheap! Most large DIY stores will sell them for as little as £50.

Cons:

• They tend to have a low OCV (open circuit voltage), so starting an arc is tricky.
• The low OCV results in an unstable arc, and this gets worse as the transformer heats up. While they will weld it is to a lower standard than any of the other types of ARC welder.
• Can't be used for special rods that require over 70V OCV (such as low hydrogen).
• Very poor duty cycle: Many of the cheap ones will weld for only 30 seconds before needing a rest for 10 minutes on the maximum amp setting.
• They are less efficient than inverter welders and will tend to require a dedicated supply to work on higher settings.
• Can't be used for TIG welding.

Verdict:

To a great extent these are a waste of money. They are the most difficult to use of any arc welder, so most DIY buyers will decide they don't like the process and give up. The duty cycles are annoyingly low. They are only really suitable for someone who wants an arc welder for very occasional use and doesn't want to spend money.