The Workhorse Improvements Over Older SCR-based Inverter Welding Products.

Background:

The first lightweight inverter-based arc welder was designed in 1976. This new machine's power conversion was based on highly reliable SCR semiconductor components (thyristors). This design has been proven successful in heavy industry for thirty years. ARCON has made several improvements over time, but has taken great care to retain all of the best features and time-proven components of the original design. The total production of the SCR-based inverter welder has now exceeded 100,000 units worldwide, and brand new units continue to be placed in harsh work environments daily.

The design of The Workhorse is based on this original design with significant improvements in function and reliability. The improvements stem from extensive experience and the feedback from the market place, especially the repair shops from around the United States and Europe.

This white-paper outlines the improvements in function and reliability that has been implemented in The Workhorse compared to what here will be called "the old design".

The decision by ARCON Welding to choose the SCR-based design for its new series of welders, instead of the now more common IGBT elements, is based on feedback from the field, indicating an up to 100 times higher failure rate of IGBT components compared to the SCR elements. (See ARCON Welding's Frequently Asked Questions)

Welding performance:

The Workhorse has a smooth, stable and spatter free arc achieved by a new output circuit

The smoothness of The Workhorse arc has been dramatically improved over the old design by optimizing the output circuits to give a smooth arc at both low and high currents.

The comparison was made by Kurt Ewy, Training coordinator, Earlbeck Corporation in Baltimore MD - " The Workhorse makes the inexperienced welder a good welder".

Other industry and distributor comments: "The Workhorse has the smoothest arc on the market, especially at very low currents." "The Workhorse arc is as smooth as silk".

Arc gouging is now allowed for all currents.

The old design was not designed for arc gouging. The voltage stress on the output capacitors was so large that they were destroyed.

The Workhorse has a built in circuit which protects the output capacitors when arc gouging, which *allows it to be used for all arc gouging at all current levels.

*POWCON® is a registered trademark of Cyclomatic Industries, Inc. ARCON Welding LLC is not associated or affiliated with Cyclomatic Industries, Inc. and its products are not sponsored or approved by Cyclomatic Industries, Inc.

The Workhorse reliability improvements

Input capacitors can sustain long time of high current welding on single phase.

When welding with maximum current on single phase, especially if connected to 480 V or 380/400 V and a phase is lost or not connected, the input capacitors maximum rated ripple current may be exceeded. If so, the capacitor can be permanently destroyed if not protected by a temperature sensing circuit. The Workhorse has a vastly improved control circuit that will much faster and more accurately detect over-temperature in the capacitor ensuring that the capacitor design life of 10,000 hours of welding is maintained. If an over-temperature is reached, The Workhorse is automatically shut off for a few minutes and the panel light blinks indicating over-temperature.

Output capacitors can sustain long time low current welding on high-current range.

The output capacitors rated ripple current may be exceeded when welding with low current on the high-current range. The Workhorse has a temperature sensing control circuit, which ensures that the internal capacitor temperature never exceeds the rated maximum temperature where the capacitor is designed to operate for 10,000 Hours of welding. When this temperature is reached, The Workhorse welder is shut off for a few minutes and the panel light blinks indicating over- temperature.

Vastly improved suppression of transients on the input power lines

The old design has varistors from phase to ground only, The Workhorse has in addition varistors between phases improving the suppression of the voltage surges on the input power lines. These additional devices limit the voltage surge between phases to a voltage lower than the maximum rated voltage for the input diodes.

In the old design varistors in parallel are used to protect the rectified DC supply voltage. Varistors vary very much in clamping voltage from device to device, which makes it non-effective to use varistors in parallel. The Workhorse has a single varistor with 7 times higher surge current capability (40,000 Amps.)

Increased SCR overvoltage protection

The overvoltage diodes in The Workhorse have increased from 16 A to 75 A, using the input diodes.

Auxiliary transformer

The auxiliary transformer of the old design is designed for 50/60 Hz. The welder is often connected to generators at remote work sites. When a generator is overloaded, its frequency drops and may stay at a low frequency of as low as 40 Hz. This causes the transformer to saturate if it is designed for 50 Hz and a dangerous over-temperature may occur. The Workhorse auxiliary transformer is designed to survive abnormal conditions and high temperatures without being destroyed.

Enhanced surge protection circuit for voltage spikes (Optional)

If desired, we can increase the surge protection when connected to power with "dirty" and powerful voltage spikes, such as mines and certain generators.

Mechanical improvements

Skates underneath The Workhorse.

The welders are often dragged by the primary cable. Even if that is not a recommended practice, that is a fact. The bottom of The Workhorse is designed with heavy duty molded upturned skates to make dragging easier and safer.

The Workhorse can be nested.

The upper case has mating indentations in the top, making nesting of two units possible for storage purposes or, strapped together, for welding purposes in the field.

Handles are recessed

On the old design the fixed upright handles were sometimes pushed down with such a force that they were punched through the top case. In addition, the upright handles made the units impossible to stack on top of each other. The Workhorse has rugged, foldable handles which recess into the top of the unit.

The corners of the case of The Workhorse are dimensioned for abuse.

A study of the old design indicates that sometimes the corners were crushed from daily wear and tear. We have now greatly reinforced The Workhorse corners to prevent this from happening.

Steel louvers make the air intake screen safer, more efficient and rain resistant.

The old design had an air intake grill made from injection molded plastic which was susceptible to being pierced by a forklift tine, thereby exposing the 700 volt heat sinks. The heat sink voltage with its 700 volt AC at 5000 Hz is many times more lethal than 480 Volts AC at 60 Hz.

When it rained, the horizontal grill louvers could cause raindrops to bounce into the inside of the welder. The Workhorse has a steel grill with louvers sloping 45 degrees downwards, making both piercing and the introduction of raindrops through the grill practically impossible.

Changing to strong steel louvers enables The Workhorse to pass IEC-60974-1/14 which is necessary to pass the CE certification .

Circuit Improvements

The EMI (radio noise emissions) filtering circuit is changed. The neutral to ground capacitor is a type Y capacitor necessary for CE marking

The input diodes have been upgraded to 1600 V

The single volt design has enabled us to redesign the main transformer. The voltage between each turn on the primary winding is now reduced from 350 V to 12 V. This will drastically reduce the arc-over risk in corrosive and humid atmospheres.

All screw terminals are coated with silicone varnish to protect against corrosion and prevent them from coming loose.