Answer:
Our SCR-inverter design was developed in 1976. When reviewing repair records from the estimated 100,000 machines sold over the past 30 years, findings indicated that the SCR component is much more reliable than the alternative IGBT inverter design.

This was illustrated by a distributor who has sold over 2000 SCR-based welders over 20 years to the shipbuilding industry, which is a very demanding environment for a welding machine. During these 20 years and 20,000 machine-years, (assuming linear increasing sales) 30 SCR's were replaced. This translates to 666 machine-years per replaced SCR.

The same company sold to the same customers 200 welders over 2 years based on the IGBT made by different companies. During this time 30 IGBTs were replaced which translates to 6.66 machine-years per replaced IGBT.

This indicates that, at this time, the SCR is 100 times more reliable then the IGBT. If this is caused by the used circuitry or a more reliable mounting of the semiconductor element is at this point irrelevant as we want to have the most reliable welder possible. We have not found a device or circuitry more reliable and giving a better weld than this SCR-based inverter.

For future products, we are involved in the development of SCRs as well as IGBTs that are specifically optimized for use in inverter welding machines.

Answer:
Our experience is that it is very difficult (and expensive) to make a sheet metal case that can survive a 5 foot drop without being bent out of shape. A polycarbonate case while being very strong, is sensitive to heat and a hole is easily melted in a polycarbonate case by a glowing electrode which of course could become a serious safety risk.

There is a 20 year/100,000 units experience with a welder with a fiber glass case. We have improved the original design based on the feedback we have received from repair shops in the USA and Europe.

We have doubled the thickness of the bottom and made skids with upturns in front and end to allow the unit to be dragged over rough surfaces.

The handles are now countersunk and foldable which prevents them from getting pushed into the case. The top and bottom design is made so the unit now can be easily stacked on top of each other.

The corners of the case are now twice as strong as in the original design.

The newly designed case has the top and bottom screwed together from underneath, preventing saltwater collection and corrosion.

Answer:
The theory behind this is that the ripple in power caused by the inverter frequency will make the weld puddle temperature change. The current in the arc has a higher ripple frequency with a higher inverter frequency, which would cause less temperature variation.

The fact is that the weld puddle has a thermal time constant of approximately a second. The WORKHORSE has an inverter frequency of 2,000 HZ corresponding to 0.0005 second, which makes it’s variation 20,000 times faster than the weld puddle’s thermal constant. Bottom line is that the ripple will have no effect whatsoever on the puddle temperature whether the inverter frequency is 2,000 Hz or 20,000 Hz

Answer:
This is very true and the WORKHORSE is designed to survive these with a big margin.

For very severe environments we offer as an option a "Generator" version. It has10 times the voltage spike survival power than our standard version. It also has a "Generator circuit" which senses abnormal generator voltages and shuts down the Workhorse for a few seconds, protecting it from failure, until non-destructive voltage levels are restored. It will flash the panel light informing the welder of a passed voltage abnormality.

Answer:
The WORKHORSE has been designed so that the frequency sensitive components will survive 40 HZ. The inverter will be shut down before it is harmed. It will automatically restart when normal frequency is restored.

Answer:
Several inverter welders have this feature. The additional circuitry increases complexity, cost and may create decreased reliability.

There is a better solution. Our market research has proven that a simple voltage selector on the front panel would work just as well with much less circuit complexity, provided the welding unit was protected would the wrong voltage selection be made. This is how we will design our future dual voltage welder.

Answer:
Constant Power has advantages in several areas, but the biggest advantage is when TIG welding thin materials. This is because the temperature of the puddle is determined by the electrical power in the arc. This power is measured by multiplying the arc voltage times the welding current. For example, when TIG welding with 100 Amperes, the welding power at 14 Volts is 1400 Watts (100X14).

What about Constant Current (CC) welding?

Traditionally, Stick and TIG welding has been done using Constant Current. When using CC, the welding machine will provide a constant current as long as the arc exists. From physics, we know that the arc voltage is determined by the arc length. When the distance is increased between the tip of the TIG torch (or electrode in Stick mode) and the material being welded, the arc voltage increases while the current remains constant. Then as the welding power (current times arc voltage) increases, a hotter puddle is produced. Good welding results using Constant Current depends greatly on having a very steady hand, especially on thin material. For example, if the Arc Voltage increases to 16 Volts (with constant current), the welding power increases to 1600 Watts (100X16).

More about Constant Power (CP) welding:

Arcon Welding Equipment designed The Workhorse welder to provide Constant Power for Stick (SMAW) and TIG (GTAW) welding. When the arc length between the work piece and the tip of the TIG torch (electrode) is increased, the arc voltage increases just as it does in a constant current machine. The difference is that the Constant Power machine will sense the increase in arc voltage and will automatically decrease the current, allowing the welding power (= puddle temperature) to remain constant. Even those with an unsteady hand can weld very thin material using Constant Power without causing burn-through. For example, if the Arc Voltage would increase to 16 Volts (with Constant Power), the welding power will remain constant (87.5X16 = 1400 Watts).

Other welding machines that provide Constant Power characteristics are big motor-generator welders, where the mechanical mass rotation keeps the output power constant. This is the reason that these big welding machines have been preferred for very precise TIG welding, such as in the nuclear industry. Now, Arcon Welding offers these Constant Power advantages in a small, portable package.