Rugged Flexibility - Why Today’s Inverter Technology Works on Construction Sites

by Bruce Chantry and Matthew Albright
The Lincoln Electric Company

Portable. Efficient. Multi-process. Rugged. These adjectives are just a few of the accurate descriptors for the benefits inverter welders have over traditional transformer-based power sources when it comes to welding in the field. Because inverter-based power sources are smaller both in weight and size than traditional transformer-based or engine-driven units, they can be ideal for use in construction applications, for practical reasons alone.

Inverters have had a role on the construction site for quite some time. However in the past, not all inverters could stand up against the harsh environments found on such jobsites. While past units were small, portable, efficient and delivered good arc response, the reliability was not the same as traditional transformer or engine-driven workhorses. Contractors used to have to choose between convenience and small size or ruggedness. That’s no longer the case.

Thoughtful and innovative design choices have made these portable, high-amperage, multi-process power sources more robust and ideal for use in extreme field environments. These changes have helped reduce the incidence of wasted time on a jobsite. Convenience is a matter of course when it comes to inverter welders – something that’s a bonus in the field.

Robust Design,
Rugged Operation
Some of today’s inverters are designed for construction applications from the ground up – with both the operator and the potentially harsh environments in mind.

First, consider the effect of high external temperatures on the overall performance of welding equipment in the Middle East or American south during the summer.

The NEMA standard for duty cycle testing of welding machines involves running a power source continuously at a specific amperage, at a temperature of 40°C (104°F) for 10 minutes. A 250 amp machine that claims 100 percent duty cycle, for example, should be able to run at 250 amps for a full 10 minutes, and maintain full amperage without a reduction in output, or worse, overheating and completely shutting down.

Temperature plays a big role on the construction jobsite. If you’re putting a deck on a construction project in an ambient temperature of 80 to 85°F, the temperature of that steel will be higher than that.

In the past, contractors simply purchased higher amperage machines than they needed to ensure their welders wouldn’t shut down in high-temperature jobsites, such as those previously mentioned. Today, ratings, such as Lincoln Electric Desert Duty™ ratings, provide ratings for welding outputs at extreme temperature operation up to 55°C at 100 percent duty cycle. Such ratings help contractors more accurately size their machines for their needs and help them save on the purchase price, compared to overbuying with a larger machine to stand up to the heat.

Another key rating also comes into play when discussing modern inverter design. The IP23 rating covers the inverter’s enclosure and refers to its ruggedness against surface and water damage. For example, to achieve this rating, an inverter is subjected to a rain shower that directs water 60 degrees from vertical while its fan is running. While the machine is still wet, it must withstand a high voltage dielectric test and an insulation resistance test.

Inverters also undergo salt, humidity, drop, jerk, impact, vibration, and other repeated life and reliability testing to confirm robust performance and durability in harsh field environments.

On the inside, some machines on the market now, such as those offered by Lincoln Electric, feature tough, heavy-duty PC boards that use surface mount technology, and feature epoxy resin-encapsulated components and protective trays that keep dust and humidity at bay. Some manufacturers also focus on mounting their PC boards vertically, rather than horizontally. The vertical orientation keeps the buildup of dust and corrosive particulate to a minimum. As a result, board failure rates are reduced.

Internal connections are another common point for failures in any welding power source, as pins and other connectors can be corroded or ruined by other contaminants. The latest generation of Lincoln Electric inverters feature a special patent-pending Molex® boot that pull over the pins and self-seal for lasting protection.

Also, instead of a fan that runs continuously to keep machines cool, some units, such as Lincoln Electric’s Flextec™ multi-process welders, have a Fan-As-Needed™ feature that reduces power consumption, dirt intake and damaging thermal cycling. Other durable features found on some machines include impact-absorbing rubber feet and sturdy handles positioned to help protect controls from damaging blows.

Beyond protective design features, the newest inverters on the market also have become more modular and user-friendly. For example, typically within a single manufacturer’s product group, the look and feel matches throughout the line. Users don’t have to re-learn which switches control what function. Everything is in the same place on each machine. Operators can walk up to a wide range of models and know how to use each one.

Reliable, Multi-Process Performance
Historically, contractors were reluctant to perform carbon arc gouging with inverters because it is a harsh, demanding process that can be hard on earlier inverter designs. To be considered a suitable replacement for transformer or engine-driven welders, engineers realized that these machines needed to be able to not only perform high and low amperage flux-cored, stick, TIG and MIG welding but also arc gouging – and possibly even CV submerged arc on some models – with complete confidence.

Construction sites needed a portable, reliable power source that can serve as a multi-process workhorse for all welding needs in any environment. Today’s re-imagined inverters deliver, offering faster arc response, smoother arc action and a more consistent bead appearance.

The latest inverter technology delivers superior welding performance across a wide range of outputs and they outperform traditional technology. Now, they also perform well on gouging – without the large physical size of transformer-based or engine-driven welders. Some of the newest machines, rated at 650 amps at 100 percent duty cycle with a range of 10 to 815 amps, weigh in at only 165 pounds vs. over 700 pounds for a single traditional power source of similar amperage. The new inverters also have a much smaller footprint.

Additionally, today’s inverters feature advanced input voltage protection – a must for high-performance use on job sites where power supplied to the machines isn’t always necessarily robust or reliable, and instead can be more erratic. Lincoln Electric worked with some large end user customers to develop the latest inverter technology so that it is capable of surviving as much as 1000-volt input spikes on the job, and their machines have survived and continued to operate.

Monitoring Capabilities
The latest inverters not only offer design features targeted to the construction market, but also provide data collection capabilities through special weld data acquisition tools, which previously have only been feasible for use in factory environments. The increased availability of mobile technology has made tracking at the construction site feasible, allowing for both monitoring of weld performance on site and post-project review back at the office.

Checkpoint Summary Screen

Traditional field welding solutions, by the nature of their simple design, previously have been unable to use software tools to store and recall procedures. They have no procedural memories and lack a reliable way to lock operators out of procedural tampering. However, rugged new add-on modules, such as Lincoln Electric’s Arc Tracker®, now permit weld parameter monitoring, providing verification of PQRs with a simple plug-and-play connection with any DC welding power source and the use of voltage sense leads.

These units immediately provide access to a wide array of data monitoring information regarding the welding arc, helping contractors deliver and verify procedures adherence, including True Energy™ and heat input verification, especially for those applications requiring heat input records. These units feature advanced digital controls to sample the welding arc parameters at extremely high speeds to deliver reliable statistics.

Construction Site Powerhouse
To summarize, while inverter-based power sources have been in the construction space for years, they have historically been associated with less rugged performance and reliability than their larger, engine-driven counterparts. Also, in the past, contractors had to pay a price premium to purchase that smaller, lighter-weight equipment for their projects.

That’s no longer the case, thanks to ongoing engineering in the inverter-based welder market. Today’s inverters combine the traditional benefits of less weight and a smaller footprint with high output and more robust multi-process capabilities, bundling high performance into a rugged design that stands up to harsh environments – and at a cost that matches similar conventional equipment.

Simply put, today’s inverter welders deliver distinct advantages over larger conventional electrical or engine-driven power sources and should be a standard tool in the equipment arsenal on any construction site.

Racking Up the Benefits
Welding crews at the Cleveland Medical Mart and Convention Center quickly discovered that efficiency reigns in multiples when they used inverter power sources in racks while welding on one of downtown Cleveland’s most prominent new construction projects.

The 1 million-square-foot, four-story Medical Mart facility will house approximately 50 permanent showrooms for companies that sell different products in the medical industry, including medical devices, healthcare IT, healthcare providers, healthcare education and more. The project also includes a 767,000 square-foot convention center with 230,000 square feet of exhibit hall space, 35 meeting rooms and a large grand ballroom overlooking Lake Erie.

Expected to transform Cleveland’s downtown when it opens in fall 2013, the $465 million complex used 11,700 tons of steel. It’s no surprise that welding has played a significant role in the job. Welding crews used 12 Lincoln Electric Flextec™ 450 inverters on the site, configured in 4-Pack Racks at various areas within the jobsite.

Rack systems allow multiple power sources to be connected with one primary power drop. The power sources are factory installed in the rack and wired to the main power distribution panel. These systems are ideal for grouping several inverter power sources in a portable industrial-grade package that makes it much easier to transport or lift around the site. Modern inverter technology makes more efficient use of incoming power. Crews can run four operators with multi-process welding capability on a four-pack rack while using less power than it would take to run three traditional power sources.

These inverter racks are constructed of heavy gauge square tubular steel to ensure added protection for the inverter welder units, yet maintain an extremely compact overall size and weight. In fact, four 650-amp inverters in a rack weigh only about 410 pounds more than a single, comparable traditional machine without a rack.

“Multiple operators can work in several different spots on the site from one source with a rack,” notes B.T. Rambeau, welding foreman for Forest City Erectors. “I had four guys running all the time going through probably 200 pounds of rod a day. It’s a north and south welding on the columns. With the rack, I could take two guys on the north and two guys to the south. We would be working constantly off of this system and enjoyed the quick start ups and crisp runs.”

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