I learned TIG welding on an old Linde unit (the model slips my mind,
it was a very large ac/dc unit - I thank my research director for
teaching me this skill. I am now in the market for a TIG machine - I
am a hobbyist gunsmith. I have read the pros and cons of the machines
out there, and need something that will weld thin sheetmetal and cast
aluminium (also thin) but also has the flexibility to weld much
thicker material if the job demands (some tripod mounts and misc
projects that come up). I decided on the Miller Dynasty 200dx, but
upon further reading saw reports that these machines may only be good
for the warranty period due to being solid state inverters... I want a
machine that will last like my boss' Linde (he bought his after grad
school) but also need that low amp stability - where do I go from here
(will the synchrowave units function ok for my needs running 5-10 amps
at the low end?) ? Any advice is appreciated.
On Thu, 29 Apr 2004 06:03:31 GMT, Ernie Leimkuhler
Assuming neither machine (Dynasty 200 DX or Syncrowave 250 DX) gets
abused, is there really a durability or longevity difference between
the two machines? It seems that the Dynasty hasn't been on the
market long enough to exhibit its repair record.
The problem is type of technology.
Inverters work great, but all the components are compressed into a much
The few boards in inverters are sealed in blocks of plastic or silicone
Each board costs about $500 to replace.
Transformer machines are larger and have more space inside.
Repairs have the potential to be much cheaper since you can replace a
$30 relay, rather than a $500 main board.
Also transformers don't get moved around as much, and having more air
space tend to run cooler.
Inverters have a 10-15 year lifespan at best, before repairs become
We have transformer machines at school that are 40 years old, and still
Parts can be hard to find, but they don't cost much.
I love inverters, and have had my Maxstar 200DX for 3 years.
Just this month it went out of warranty.
I treat it very well, but it still makes me think about selling it for
a newer one.
10-15 years of getting used daily?
What kills inverters most efficiently?
Jostling from being moved? Grinding dust / iron filings in the airstream?
Running into the duty cycle too often?
I'm hoping that not abused, I can get more than 10-15 years out of
a TA185. Used a few times a month as opposed to daily like your Maxstar.
Hopefully age itself isn't too much of a killer.
When you buy an old car or m/c, you figure on replacing the rubber bits.
Speaking of old cars... What model body/engine is your Toyota(s)?
The internal parts are not made from adamantium.
Materiels age, insulators dry out and plastics deteriorate.
The most common cause of death for old tranformers is whenthe varnish
on the transformer wires breaks down and the whole coils shorts out.
The same thing can happen to a inverter, just on a smaller scale.
In order to make sure I wasn't just making stuff up, I just had a chat
with one of my welding machine repair buddies.
He said that an inverter that was left in a shop, running from one
voltage all the time, that had the dust blown out regularly, and was
never bumped or knocked around, should live indefinitely.
The most common parts that fail are the IGBT power diodes, which should
be available for the next 10-15 years as replacement parts.
He sees longevity as being limited by the availablility of replacement
As he said:
Transformers have pretty much reached their ultimate state.
All they change now are the interfaces, and figuring out how to make
some of the parts cheaper.
Inverters are still evolving, and have yet to reach the state of
electrical perfection that the transformers have reached.
The most coommon causes of death for inverters are:
1. Physical abuse, which breaks parts free inside cauising internal
2. Dirt and dust which prevents parts from cooling properly.
3. Running from many different voltages all he time.
So you can see that what kills inverters is being used as portable
machines at multiple jobsites, being tossed in and out of trucks, and
not being cleaned.
A inverter that lived in a shop and never moved, should live a long
He did recommend having it professionally cleaned every 5 years.
I own 3 toyota trucks.
Truck 1 is my old '85 1-ton, longbed, 22REC Fuel Injected.
Truck 2 is my new '86 1/2-ton, long bed, Xtra-cab, 22RE, Carb.
Truck 3 is an '85 1/2-ton, shortbed that I bought for parts for $100
So far I have yanked the engine from Truck 3 and installed it in Truck
1 to get it moving.
I plan on rebuilding the engine from Truck 1 and re-installing it.
I will then clean up the engine from truck 3 and put it back in truck 3.
Truck 3 will get rebuilt and sold to my neighbor.
I swapped the rear springs in truck 2 for those from an '86 4WD, so now
it is closer to a 3/4-ton.
Truck 1 will be converted to a flatbed, so I have a 1-ton flatbed for
hauling large things.
Truck 2 has the overhead rack for long things.
I once had a Millermatic 200 (which I know is NOT an inverter machine, but
anyway .................) that I owned for 13 years. I used it for
commercial production of ornamental metal. The ONLY thing I did to that
machine in 13 years is change guns. I was really surprised that the
contactor points lasted that long, and an unknown time after I sold the
Point is, IMHO, that anything that stays in a shop lasts longer. And
anything that is only used by the owner and not employees or students, lasts
Just musing ...........
wrote:> The most coommon causes of death for inverters are:
From what I've read on he inverter welders,
and with experience in high-current choppers
and inverters for subways (500-1,000 Amp),
the most predominant cause is exceeding duty
cycle. Thing is, anything that even "has" a duty
cycle in the first place tells you that it is under
rated in the first place (for the current ranges
that fall under the 100% duty cycle rating).
In my opinion, I'd say that you are at the
mercy of the electrical design of the unit.itself.
i.e. how they design the snubbing circuits,
what part of the derating curve they design
the rise-times of the switching elements, and
the switching rates, thermal conductivity of
the heat sinking, etc, etc, and the switching
device itself (manufacture, part selection, etc).
But yes, as always, physical abuse does play
into it, I just happen to think that the above
superceeds that. At Westinghouse, and for
chopper/inverter design for traction motor
control for subway systems, (Bart, WMATA,
NYCTA etc), the inverters/choppers were
designed such that the max real world current
current at (even at 100% duty cycle) was almost
half of what the inverter was designed to do
(at 100% duty cycle). ergo, FLA w/ fully loaded
car was like 650 Amps, but with switching elements
rated at over 1,200 Amps (RMS), the inverter
could handle over 1,000 Amps at 100% duty cycle.
Course in these situations, there are strict requirements
for MTBF (Mean Time Between Failure), and rated
total mission time (since these are very high dollar items.
This would be equivalent to never taking a Thermal Arc
ProWave 185ST over about 65 Amps, even though its
rated at about 110 Amps at 100% duty cycle, and 165A
at what, 20% dutcy cycle or something ? So its longevity
lies largely in the design. Sounds like these welding
inverter designers (ThermalArc, Maxstar/Dynasty etc)
have indeed found a tradeoff point of derating vs. "over"
rating, MTBF, and total mission time and cost.
But I do believe that an additional factor really does lie
in how it is used, and at what current.
These new fangled IC's and plastic Transistors, and capacitors - stuff like that
dye on the shelf. Tubes hang in there - sometimes glue came apart.
Normal failure mode is usage - current through a part physically more atoms away
from the part they need to be.
Just hits from the power line might do it. - sit there and the one next to it
kick the power line and it rings in several box transformers.
A FA - failure analysis would have to take place...
Martin Eastburn, Barbara Eastburn
@ home at Lion's Lair with our computer email@example.com
With electronic equipment it is electrolytic capacitors. They don't age
gracefully, and when they fail, they often take other components with
them. In high current applications like welders, electromigration is also
an issue. That takes out semiconductors. Semiconductors are also
very sensitive to spikes and surges.
Running with inadequate cooling, or near duty cycle limits, will accelerate
aging related failures. Because the welder manufacturers seem to be in
a competition to reduce the size and weight of inverters, inadequate cooling
has become a serious issue. Not enough air circulation, not enough heatsink
area, and not enough thermal mass are real problems for equipment that is
already sensitive to heat stress.
Components which might have a nominal 20 year life at 70F, will have
exponentially shortened life at elevated temperature. In other words,
they might only last 2 years at 100F, or 3 months at 120F, or 1 hour
at 170F. (Those are just illustrative numbers, not to be taken literally.)
OTOH, the big old transformer boxes have huge thermal inertia, plenty
of room for massive heatsinks, and large fans. They're also simpler, with
much less to go wrong in the first place.
The other issue with inverters is obsolescence of parts. When there is
a problem, the components needed for the repair may be long out of
production, and the complex and compact circuit may not allow a
substitute part to be fitted. Electronic components, particularly complex
semiconductors, now have a very short production lifespan. 18 months
is typical before they're replaced by a new generation. It isn't unusual
to not be able to get semiconductor parts for equipment that is only
3 years old, because those parts aren't made anymore.
OTOH, conventional transformer design is very mature. The same part
may be in production for decades. Also, transformers can be rewound,
so even if a new replacement part isn't available, you can have the old
part rebuilt by any rewind shop.
However, as more features proliferate, even the transformer machines
have had complex control circuitry added to them. So you could still get
stuck with an unrepairable machine if a component on the control board
In consumer electronics, we've already passed the point where repair
is a practical option. When your TV, stereo, or computer dies, you
just go out and buy another because a repair, if possible, would cost
nearly as much as a new unit (which likely would have better performance
and more features anyway). It is getting to that point with industrial
electronic equipment too.
We're in the process of replacing a perfectly satisfactory audio console
at work. The old one is less than 10 years old, but we can no longer get
repair parts for it. This isn't the console manufacturer's fault, the component
suppliers just don't make the parts anymore. The new console will cost
$270,000. That's outrageous, but we can't live with a console we can't
keep in repair, so we've got to do it.
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