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  1. #1
    Join Date
    Feb 2006
    Posts
    3,711

    Default Transformer Versus Inverter MIG Machines

    Hello to all,

    I recently received an email inquiring about inverters and transformer type welders. This person has seen this information on a "reputable website: "Transformer machines have better wetting action for MIG welding than do inverters hands down. The industry is pushing inverters at the expense of weld quality".

    What does anybody think about this? Following is my response:

    I have never really considered the wetting action of a transformer machine versus an inverter machine. However, I can relate to real welding experiences and let you take it from there. I have welded with transformer machines much longer than inverters, but all around prefer the inverters:
    They are much more portable, will run on most any input supply, easy on the electric meter, and I like the arc better. This is my personal preference.

    Precluding these experiences is basic theory of operation. A transformer machines uses AC line voltage oscillating (AC sine wave crossing form negative to positive) at 60 cycles per second or Hertz (HZ) named for the gentleman you discovered the phenomena. Inverters multiply this 60HZ incoming power many times to a much higher frequency yielding higher current output in smaller machines, inherently different arc characteristics, and ease of use (learning curve).

    About 5 years ago I mainly did light shop fabrication and used a Miller XMT 304 (inverter) with a Miller 22 wire feeder (the predecessor to the current 22A model. This machine had and INDUCTANCE knob for the MIG which made the puddle more fluid as you increased the inductance. In the stick mode this became the dig control and increased the arc force for hard to burn rods like the 6010. With that being said I mostly kept the inductance knob on the low side around 1/4 turn up. If I went any higher the puddle was too fluid! I did crank it midway once burning 309SS rods when welding 304 SS flat bar to some A36 carbon steel.

    My mobile welding is done with a Trailblazer 301G. It has a 4 pole 3 phase arc which for this comparison it's arc is 120HZ or twice that of a transformer or more basic engine drive (like the Bobcat 225NT). I used to weld with a Bobcat (typically like a 60HZ arc output) and for me the Trailblazer arc wins hands down.

    Here's my conclusion based on experience. The transformer machines weld well. However, if you are new to the industry I suggest you try both before buying. I believe the inverters are the way to go for me. The XMT 304 has one of cleanest easiest burning arcs of any machine I have ever used including the old Miller TS252 which they have just discontinued this year. It was an awesome MIG transformer power source with tapped slopes (relative to inductance for sake of comparison). I don't think Miller makes any adjustable slope machines anymore. The closest thing I have found is adjustable inductance on some of the inverters.

    Think about this. Miller keeps coming out with bigger and more power efficient inverters like the Invision 456 MP MIG/STICK machine at 600 amp output and 450 amps at 100% duty cycle on 3 phase power or the Invision 456P MIG only with similar output: 450 @ 100% and 565 amps at 60% duty cycle. All these inverter machines are capable of high amperage output with high arc voltage as well. This tells me the wetting action is excellent.

    The statements made about inverters and transformer machines may be true if you are talking about the first inverters to hit the market. They had bugs to be worked out. Now the bugs are out and they are great machines. As a side note all portable plasma cutters like the Miller 625, 2050, 3080 ; Hypertherm Powermax 600, 1000 ; ESAB 650, 875, 1150(not sure of this model number) are all inverter machines. My guess is the wave of the future.

  2. #2
    Join Date
    Sep 2005
    Location
    Evansville, IN
    Posts
    2,348

    Default

    Hawk: I must agree that inverters have come along way. I am still taking classes in welding and use a 456mp, fantastic piece of equipment, if money were no object I would own one. My comprimise was to a mm210 which still is a transformer I believe, and the arc charactoristics are very similar on the typical easy mild steel stuff. The inverter shines the best in my mind in the fine tuned odd stuff 304ss and real thin where pulse is needed. I am currently using this machine in a stick class to help hone skills already learned. If someone thinks otherwise they need to use one in a production setting then they will change their mind.

  3. #3
    Join Date
    Nov 2003
    Posts
    4

    Default

    Our Miller dealer brought out a new Demo Inverter pulse mig unit to try on a production job welding fuel tanks. Our goal was to cut down on spatter. It did fine on the spatter, and also weld time dropped by 25%. Weld quality also improved as all were pressure tested and all passed. (We would find an occasional porosity leak using transformer type.)They are a little pricey at over $7000, but for us a no brainer. Better weld, faster,less cleanup. We ordered two to start with.

    Nitehours

  4. #4
    Join Date
    Nov 2003
    Posts
    4

    Default

    Our Miller dealer brought out a new Demo Inverter pulse mig unit to try on a production job welding fuel tanks. Our goal was to cut down on spatter. It did fine on the spatter, and also weld time dropped by 25%. Weld quality also improved as all were pressure tested and all passed. (We would find an occasional porosity leak using transformer type.)They are a little pricey at over $7000, but for us a no brainer. Better weld, faster,less cleanup. We ordered two to start with.

    Nitehours

  5. #5

    Default

    It looks like who wrote the article had a narrow understanding of inverters. In some cases it was true that transformaer machines would wet out different. This was due to the inductor or stabilizer coil magnetics NOT the transformer. The transformer had a little to do with wetting by how it was wound wich determined if it was a CC or CV transformer. As HAWK mentioned, the XMT has an inductance knob for setting puddle fluidity and works rather nice. It gives the operator flexability when doing out of position welding somthing that had to be "worked around" with a transformer unit. Remember, too much wetting is bad and gives incomplete toe tie in. The weld puddle just sits on top of the base metal. Inverters have come a long way and don't deserve an incomplete analysis. I own both a transformer type unit and inverters. They both have their place in my shop. I will say when welding the real light gauge sheet metal, like 22-26ga, the transformer unit has a lower bottom end where the inverter unit was never designed for that thin of material. That may change with the development of new all-in one inverter MIGs.

    Andy

  6. #6
    Join Date
    Sep 2005
    Location
    Millstadt IL
    Posts
    483

    Default

    Hi Andy, I was wondering if you could expand on "new all in one inverter MIGs". Are there features coming that are more than just expasions of what's available now? I know you can't give away the farm but the wording really made me think. Thanks, JEFF

  7. #7
    Join Date
    Feb 2006
    Posts
    3,711

    Default

    Jeff,

    I think he is referring to something like the MM251 with an inverter power supply-perhaps even a 300 amp inverter all in one?

  8. #8
    Join Date
    Sep 2005
    Location
    Millstadt IL
    Posts
    483

    Default

    I,m sure your right, I am used to thinking of an inverter as a stand alone supply and didn't put the two together until I read your post. Suddenly looked so simple! Thanks, JEFF

  9. #9

    Default

    Actually the 251 is a transformer unit with solid state control using SCR (silicon controlled rectifier). It lets more or less current from the transformer depending on what settings you are at.
    As far as inverter all in ones, I'm sure they are on the way

    Andy

  10. #10
    Join Date
    Feb 2006
    Posts
    3,711

    Default

    Andy,

    I am aware the MM251 is a transformer machine with the SCR output. However, I was thinking perhaps Miller is coming out with an "All-IN-ONE" machine similar to the MM251 with an inverter power supply. It was for example in response to Jeff's prior question.

    Thank you for the information.

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