Author Topic: Homemade IGBT MIG welder with ATX PSU parts. [blown yet again][blown count: 5]  (Read 28560 times)

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Offline RefrigeratorTopic starter

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Went to Aliexpress and found out what the diode was supposed to be and it's a RURU15060 (or 15080, 15090, 15070 whatever) and this whole diode business seems like a bit of a rabbit hole.
The 150EBU04 marked diodes in the TO-218 package are cheaper than the RURU15060 but even the RURU15060 fakes are made in the TO-247AC package.

Ps: one good thing about aliexpress is that the reviews do help out quite a bit, especially when buyers include pictures.
« Last Edit: July 09, 2019, 05:07:40 pm by Refrigerator »
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Offline strawberry

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https://www.aliexpress.com/item/32815709325.html
found this wire feed motor, is this any good? are all euro type connectors same size? and what kinda torch to choose?
 

Online tautech

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Offline RefrigeratorTopic starter

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Offline strawberry

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or this SSJ-4C https://www.aliexpress.com/item/32826045278.html
I dont know what size fits best for 5/15kg spool
I think 0.6mm roller could do the job.
15AK MIG torch seems got thin copper wire for 180A https://www.aliexpress.com/item/32849629353.html
 

Offline mikerj

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https://www.aliexpress.com/item/32815709325.html
found this wire feed motor, is this any good? are all euro type connectors same size? and what kinda torch to choose?

It certainly looks a lot most robust than the all plastic versions, though the lack of 0.6mm wire support is a little annoying for use as an upgrade for cheap MIGs.
 

Offline RefrigeratorTopic starter

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or this SSJ-4C https://www.aliexpress.com/item/32826045278.html
I dont know what size fits best for 5/15kg spool
I think 0.6mm roller could do the job.
15AK MIG torch seems got thin copper wire for 180A https://www.aliexpress.com/item/32849629353.html
looks like 20-25mm2 wire.
I have a blog at http://brimmingideas.blogspot.com/ . Now less empty than ever before !
An expert of making MOSFETs explode.
 

Offline RefrigeratorTopic starter

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Got 30% of my money refunded from the previous crap diodes and bought four of these diodes:
https://www.aliexpress.com/item/1720411447.html?spm=a2g0s.9042311.0.0.14194c4dvOxU16

According to user reviews these should handle 30A per leg and breakdown voltage is around 170V, there are also some people who tested the recovery time and such. Two in parallel on each side of the half bridge should in theory handle 120A.
Too bad the shipping from aliexpress is notoriously slow so i'd have to put this welder project on hold for a while, bummer.

Anyhow, i developed a LM393 SMPS controller for two switch forward application that i will be using for my mini spot welder project.
I have a blog at http://brimmingideas.blogspot.com/ . Now less empty than ever before !
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Offline RefrigeratorTopic starter

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https://lcsc.com/product-detail/Schottky-Barrier-Diodes-SBD_IR_80CPQ150PBF_80CPQ150PBF_C3044.html
Looks pretty good at first glance, but the shipping and handling fees make it impractical for small orders.

I have a blog at http://brimmingideas.blogspot.com/ . Now less empty than ever before !
An expert of making MOSFETs explode.
 

Offline strawberry

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Welder 200A rectifier with two RC snubbers 10n(MKS4 2kV) 2.2R(4x 10R wirewound)
Y2 10n 300V
8x 60A 300V fast diodes TO-247
 

Offline RefrigeratorTopic starter

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The diodes are finally here, took 11 days from being shipped to arriving at my door (the record so far is 9 days from ordering to arriving at my door)
That aside i'll go put the diodes in and fire the welder up.
Also i noticed that i need to put a freewheeling diode in the welder because i added the inductor.
I have a blog at http://brimmingideas.blogspot.com/ . Now less empty than ever before !
An expert of making MOSFETs explode.
 

Offline RefrigeratorTopic starter

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Assembled the welder back together and did a quick test on 12V, the output measures 4V and i get 3.8(-ish) amps when i short it out with my DMM.
So my welder is back and ready to rock and roll, this time i'll have to whip out the variac to test it out.
Before assembling i also measured the diodes by connecting them in a voltage feedback loop in a high voltage boost converter.
This way the output of the boost converter would be whatever the breakdown voltage of the diode is.
All of the diodes came in at around 130V, considering the current flowing through them is much lower than rated at 150V i think these diodes should be allright.
I have a blog at http://brimmingideas.blogspot.com/ . Now less empty than ever before !
An expert of making MOSFETs explode.
 

Offline RefrigeratorTopic starter

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It blew up again, goddammit.  |O
Had my brother hold the trigger pulled while i had my DMM measuring the output along with a current clap on the mains input.
As i increased the voltage the output settled at 19.54V but my current clamp was measuring between 1 and 2 amps idle.
That's about 300W going into my welder somewhere.
My Brother then had the bright idea to release the trigger and pull it again, which instantly blew the welder up. :clap:
I hope that only one MOSFET blew because i only have one spare.
The diodes are shorted out yet again so i guess 150V was not enough.
Anyways i'm off to aliexpress to find some more, at least there's some improvement i guess.
I have a blog at http://brimmingideas.blogspot.com/ . Now less empty than ever before !
An expert of making MOSFETs explode.
 

Offline patrick1

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the idea might corrupt your plan abit, - but away... how about a RC LIPO or LION Pack in paralell with the output.... super caps might be ok too.....

btw i love your ambition ... but its verging on insanity...  a home made reliable transformerless? welder.

---  i want too say too, the best arc welding experience i have ever had, is with car batteries, - 24V... it so smooth like butter. so nice.
 

Offline T3sl4co1l

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Some voltage and current monitoring sensors, and protection latches say, might be in order, yet?

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Offline RefrigeratorTopic starter

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the idea might corrupt your plan abit, - but away... how about a RC LIPO or LION Pack in paralell with the output.... super caps might be ok too.....

btw i love your ambition ... but its verging on insanity...  a home made reliable transformerless? welder.

---  i want too say too, the best arc welding experience i have ever had, is with car batteries, - 24V... it so smooth like butter. so nice.

There's no insanity here just a lot of learning (through even more failing).
Also i'd rather not use batteries for welding, good batteries are expensive and bad batteries wouldn't work.

Anyways, i took the diode bridge apart only to find out that just one of the diodes had failed.
One of the diodes in the double diode shorted out throwing the magnetic field in my transformer out of balance and into saturation and blew the MOSFETs right out.

I did some calculations and assuming i get 4V out with 12V in i get a ratio of 1:3, this means that with 340V (rectified 230V) i would see around 113V.
Since it's a half bridge the diodes would see at least double making it 226V that's not including any current spikes so i should take 250V as my bare minimum.

Also digikey came in handy with their filters, with them i can find actual part numbers rather than write "80A diode switching" in the aliexpress search  ::)

Ps: cracked the failed diode apart to see what's inside. There are two silicon dies, each 2.5x2.5mm ( 2x6.25mm2 in total) both with two bond wires each.
Two bond wires should be ok at 40 amps, the silicon die has a current density of 6.4A/mm2, in comparison the TO-247AC (150EBU04) diodes were 4.16A/mm2.
I have a blog at http://brimmingideas.blogspot.com/ . Now less empty than ever before !
An expert of making MOSFETs explode.
 

Offline RefrigeratorTopic starter

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Some voltage and current monitoring sensors, and protection latches say, might be in order, yet?

Tim

I had a current sense transformer with current limiting circuit ready but forgot to put the CST onto the power transformer primary wire.  :-[
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An expert of making MOSFETs explode.
 

Offline patrick1

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depending on how many transistors you have too burn ;-D.... i would suggest trying to put a motor start capacitor across the transformer primary ... something between 1-10uF.  ...

its really hard too protect transistors from this kind of abuse, and im pretty sure a simple diode wont do the job, even a super fast one, -  i have never been satisfied with ultra fast dioes for snubbing, - its plain too see on the scope, they only work 80-90% of what you want them too do... especially if you have a fast offtime.

and ferrite inductors are your friend. like the little torroids you have before mains SMP circuits...   i would put them everywhere, even one or two turns of your power wires, before and after the transformer, and after the ESR caps, before the arc. stick them everywhere ;-D.   - it has got many of my ambitious projects back on track several times...
 

Offline xavier60

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A schematic would make it possible to follow what is being done.
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Offline strawberry

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isnt that your voltage is too high for MIG welder. arc voltage should be 30V max
 

Offline RefrigeratorTopic starter

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isnt that your voltage is too high for MIG welder. arc voltage should be 30V max
It's an inverter welder, the diodes see high voltage (not mains of course) impulses, which then get smoothed out by the inductor, very similar to a buck converter.
The 4V i got were at whatever the max duty cycle (because it was undervoltage) i set the welder to was (85% i think), assuming 1:3 ratio between primary and secondary voltage i would get 113V when running on mains at that max set duty cycle.
If 113V = 85% then to get 21V (common MIG voltage) the controller would reduce the duty cycle to roughly 16%.
Also since during the test on 12V the welder was basically unloaded (except for the 100Ω idle load resistor) i can assume that 4V was also my peak voltage and therefore i can also assume that 113V would be the peak voltage on mains.
I have a blog at http://brimmingideas.blogspot.com/ . Now less empty than ever before !
An expert of making MOSFETs explode.
 

Offline RefrigeratorTopic starter

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A schematic would make it possible to follow what is being done.
I planned to release the schematic in my blog as soon as i finished the welder because i kept changing the design and component values constantly.
But i do have a crude one drawn (as a guide when soldering), although i doubt that it would be very useful.


 
Ps: please excuse the crudity of the schematic, last time i used KiCAD was years ago.
I have a blog at http://brimmingideas.blogspot.com/ . Now less empty than ever before !
An expert of making MOSFETs explode.
 

Offline strawberry

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should be ~45V
for scratch start stick welder 113V is fine
 

Offline RefrigeratorTopic starter

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should be ~45V
for scratch start stick welder 113V is fine

Google says 12 to 30V for MIG
I have a blog at http://brimmingideas.blogspot.com/ . Now less empty than ever before !
An expert of making MOSFETs explode.
 


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