High Voltage Forum
High voltage => Transformer (Iron Core) => Topic started by: rikkitikkitavi on July 11, 2018, 04:08:30 PM
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I have a couple of huge transformers (2kVA 20*2V) -C-core that is.
but it is the normal type, ie not possible to install magnetic shunts. I have some large inductors (reactors)
I have humungs large rectifiers (400V 200A *16pcs) and heatsinks to match. Might even have some thyristors fitted for this...
A simple setup would be to use it as a current limited output for a MMA (stick) welder, AC or DC.
But it is difficult to adjust the output current this way.
Also, the circuit needs to be designed with quite a large inductance in the reactor to compensate for the large open circuit voltage used for arc striking (about 50V+) compared to operating voltage on arc (about 15-25V)
One option is to use one of my even humungouser variacs (25A, ie 5kVA) to adjust output voltage and hence current draw as the welding arc voltage is not so affected by current through it.
This leads however to a less than mobile equipment. All together it packs up to 60 kg+ without casing. Or weelbarrow...
I never intended to have a inverter style portable welder but what options are there to replace the variac? How to build a variable inductance for current limit easy way?
I have also some iron cores EI-150 size etc, and a good set of angle grinders :)
What ideas to use for increasing the voltage for arc striking but still having a low voltage output?
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Sounds like an awesome project. I'm not big into welding but one thing you can try to get a higher start voltage is to have a HF start box. This would allow a few kv to jump from the stick to the work surface to get an easier start, similar to the way a tig welder initiates the arc.
A quick google search has found this:
https://www.dudley.nu/projects/hfstart/
i had to repair the hf start in my tig welder and this is what i replaced the step-up transformer and circuitry with:
https://www.ebay.com.au/itm/Boost-Step-up-Module-High-voltage-Generator-Converter-DC3-7v-7-4v-to-400KV-EU/222903670891?hash=item33e618186b:g:H8kAAOSwXXVavZbv
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Hmm, good idea.
Using a high voltage design, low resistance reactor in series to block the voltage but the problem is that it needs to block only the HF . This is how any normal TIG is used.
DC welding , typically electronic inverter to be able to control current properly and with inert electrodes and protection gas.
It can therefore only be used with DC, but fortunately most MMA welding is used with DC (AC demands AC welding pins) , either positive or negative to the work piece.
Will look into it further. The protection reactor might demand some design for high impendance and high voltage design at HF, but low impendance at DC.