Author Topic: Welder transformer replacement  (Read 322 times)

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Offline AdamB

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Welder transformer replacement
« on: June 14, 2018, 03:03:47 pm »
Hi all

I am interested in replacing the transformer in my entry level 90amp MIG welder.
https://ozito.com.au/products/90amp-gasless-mig-welder/
This is the basic model sold all over the world. The most common modification for this type of welder is to rectify the output and add shielding gas capabilities so solid core wire can be used. I am planning on making these modifications but first, I would like to add a larger transformer from an old TIG welder I don't use. I know that TIG welders are constant current and Mig welders are constant voltage I am just wondering if the transformers are different or if there is a circuit on the output that keeps the voltage output constant like capacitors.
Photo of welding circuit:
http://sbrowne.me/welder-wiring-diagram/chicago-electric-90-amp-flux-wire-welder-68887-page25-wiring-diagram/

Sorry if this is confusing I'm new to this forum
 

Online richard.cs

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  • Electronics engineer from Southampton, UK.
    • Random stuff I've built (mostly non-electronic and fairly dated).
Re: Welder transformer replacement
« Reply #1 on: June 14, 2018, 10:13:23 pm »
Usually constant current in a welding transformer is achieved with magnetic shunts in the transformer. These are usually adjustable mechanically (they slide in and out) to change the current and it may be possible to completely remove them. If the adjustable shunts can be removed, and if there are no fixed shunts (sometimes these can be knocked out with a punch but it it quite easy to damage the windings when doing so) then the transformer will behave as constant-voltage, but only at one fixed voltage. Unless the transformer has multiple taps and a fixed but removable shunt (at opposed to no taps and an adjustable shunt) you will only get one constant-voltage power level.

Do you have photos of the transformer you want to use?
 
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Offline tpowell1830

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Re: Welder transformer replacement
« Reply #2 on: June 15, 2018, 08:38:27 am »
I have no experience with this, however 'TPAI' rebuilds these pretty often, maybe you can find one of his videos that will help.

https://www.youtube.com/channel/UCDbWmfrwmzn1ZsGgrYRUxoA/videos

Hope this helps...
PEACE===>T
 
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Offline Stray Electron

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Re: Welder transformer replacement
« Reply #3 on: June 15, 2018, 11:53:59 am »
   You need to go look at the Welding Web forum.  They have a long running discussion about ways to upgrade the HF welders.  And plenty of comments about why it's not worth the effort!
 

Offline AdamB

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  • Country: au
Re: Welder transformer replacement
« Reply #4 on: June 15, 2018, 01:50:51 pm »
Thanks all for the replies.
 turns out the 90 amp transformer in the machine has no shunts.
I should be able to remove the shunts without damaging the windings as I've had experience with MOTs.
I'm going to either use the output amp adjustment circuit in the old TIG welder or I'm going to build one with the circuit from Dansworkshop. One more question; if I remove the shunts should I push the secondary winding down so it is sitting on the primary like in the picture below:
or should I leave them where they are? (BTW the photo is the transformer in my machine)
« Last Edit: June 15, 2018, 01:57:57 pm by AdamB »
 


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