# High Frequency Start Arc Generator For Pulse Arc Welder

A little back story - I'm a network security engineer turned bench jeweler. I built a capacitive discharge spot welder. It's an awesome unit, and works great, but it's not exactly what I need it to be. It's a resistance welder, which means that the resistance of the workpiece generates the weld heat. Gold and silver (the metals I work in), are very very conductive to both heat and electricity. I need to convert the unit to a pulse arc welder. For reference look at the Orion welder line by Sunstone Engineering, the PUK line by Lampert, or the Pulse Arc line by ABI.

To convert the unit to pulse arc, all I need to do (in theory) is boost the voltage above the breakdown voltage of air. It has a 3 farad main bank at 25 volts making it's an 800Ws welder when charged to it's safe max. The main bank can be charged to anything from 0 to 25, with 2 output pulses anywhere from 0ms to 35ms each. The breakdown voltage of air is about 370 volts.

The unit has a main control board that interfaces with a mosfet switching board that uses 18 75v @ 209A mosfets. Basically, it just takes 5v pulses from the control board and turns the mosfets on and off accordingly. I'd like to build a daughterboard that will sit in between the two, and switch a high frequency source on then "pass" the 5v control pulses along to the mosfet board.

This should create an ionized plasma channel through which the weld energy will then travel.

So, two questions.

1) How do I create that high frequency source? I could use the tried-but-true automotive ignition coil method. But that seems... crude. There's got to be a better way.

2) How do I protect the rest of the circuitry from being fried to bits by the high frequency addition?

• Just a note, you say it is an 800W unit, I believe you meant Joules. 3F at some 23V is 800J, which discharged in .1ms (0ms seems a little too fast) leads to a whopping 8MW. Commented Feb 28, 2016 at 10:26
• @VladimirCravero he says "Ws" for watt-seconds, i.e. Joules. But I agree, correct units to be preferred.
– user16324
Commented Feb 28, 2016 at 10:59
• I thought it was some fancy plural form of W... English can be odd sometimes Commented Feb 28, 2016 at 11:16
• Just a thought; why do you need the HF add-on at all? You're already using a short-pulse power source at 0.035 max duration, so why not just add a flyback xfmr & drive it by the output from the MOSFETs? Commented Feb 28, 2016 at 13:27
• This is hardly an answer, so I'm putting it in comments. There is some work already done by another individual so I'll link that here: pulsearcwelder.blogspot.com/2012/08/… . I'd also like to point out that you will need Argon gas as Oxygen and Nitrogen will not work so well from what I've read. Good luck.
– Dave
Commented Feb 28, 2016 at 16:05