DC High Current PWM Mig welder

Discussion in 'Analog & Mixed-Signal Design' started by stobby, Oct 10, 2018.

  1. stobby

    Thread Starter New Member

    Jun 20, 2018
    Hey everyone first time posting in a while. Hopefully this is in the right Forum section. Admins feel free to move.

    Here's the Story, I have a 250amp transformed DC Mig welder, that i have been using specifically for Aluminium welding. It has very basic stepped voltage control with 6 settings. As such this makes it either too 'hot' or too 'cold'. Here's a pic of the machine, Note the access to positive and negative outlets.

    I want to add pulse function to this machine and possibly double pulse, Like many other high end machines have. which will allow me to set: 1.background current, 2.peak current, 3.frequency.

    Single Pulse waveform
    pulse mig.JPG

    Double Pulse Waveform
    double pulse mig.JPG

    So in short i Have a low voltage (15vdc-20vdc) high current power that i need to Pulse width modulate.

    I thought possibly a couple of modular style mosfet's or IGBT's having their gates controlled by a square wave signal generator. I am reasonably comfortable with PIC chips if necessary

    Surprisingly there's not a lot of information around about the design of pulse welders.

    Kind regards, Brent.
  2. shortbus

    AAC Fanatic!

    Sep 30, 2009
    There may be other things that are effecting your welding of aluminum. #1, is what gas are you using? #2, is AC works much better with aluminum than DC.
  3. stobby

    Thread Starter New Member

    Jun 20, 2018
    In almost every case mig is always DC, Tig is more often balanced ac. I am running 100% Argon 20-25LPM.
    I am using 5356 wire, 1.2mm diameter.

    Here's a quick little YouTube clip to explain better than i can.

    Kind regards, Brent
  4. karzo94

    New Member

    Apr 3, 2018
    You can use open collector FET driver https://store.ncd.io/product/pca963...ctor-8-bit-pwm-fet-driver-with-i2c-interface/ allows 8-Bit proportional control of high-current loads using I2C communications. It consist of BUK98150-55A which is capable of controlling up to 55VDC and 5.5 Amps of current (8 Watts of Heat Dissipation), making it an ideal choice for most low-voltage DC application.
    I guess this kind of application will be useful with MIG welder for receiving the pulse input wirelessly.
    Last edited: Oct 12, 2018
  5. stobby

    Thread Starter New Member

    Jun 20, 2018
    Hi Karzo, The concept of that is fantastic however calculating its load capactiy it can only handle ruffly 300w.
    My usual welding current range is around 19v - 120amps. (2280w). However it would be nice to have it handle the full potential of the machine (250amps).

    kind regards, Brent.
  6. stobby

    Thread Starter New Member

    Jun 20, 2018
    Would it be possible to use one or a couple of these pwm controllers in series, However modify the board to controlled by a signal generator.

    Here's The PWM

    And Here's the Signal generator

    signal generator.JPG

    Kind regards, Brent.