Welder triac adjuster.

Hi There

I have a welder who has broken trafo, and I want to make a new one, this time with a triac amp adjuster on the primairy who is posted here
around, I have found a schematic also but can I use the torch button with that ? it is a co2 welder and I do not now if the triac get in problem when
I switch on and of on the primairy where this adjuster is connected. Or is it better to use a secondairy scr system?

I have a bunch weld inverter schematics from 100 to 140 amp, and have a core also, maybe this is even better way to go.

thanks in advance.

kees

I think it is better to use a secondary SCR system. The fact that the mains is still connected to the transformer primary will help to damp out the back EMF from the transformer. If you switch the primary, you will be relying on the arc. I can not see any schematics.
Frank

chuckey said:

I think it is better to use a secondary SCR system. The fact that the mains is still connected to the transformer primary will help to damp out the back EMF from the transformer. If you switch the primary, you will be relying on the arc. I can not see any schematics.
Frank

Click to expand...

Thanks.

I have seen welders has most of the time SCR on secondairy, I talk about older ones because it go more inverter like ones.

I need a formula to get the amps needed on a 40 % duty cycle basis, I do not find them easely.

With this duty cycle I can use smaller trafos, and thinner wire, so I can try to fill the trafo core more efficient.

I will in future go build a inverter for in the Co2 welder, arcs are better,, more stable.

I go try to find a SCR secondairy, you are right back emf can give trouble for the triacs or thyristors, and the need of big ones,
however all trafo co2 welders has a relays in the primairy winding who go on and of all te time.

What is best I try both.

I have bought this trafo, 18 kilo iron, 16 x 13 x10.2 cm.



What concers welder inverter I do see some here, but normally trafo uses litze wire, why some do use copper strip
for secondairy instead? no heat problem with skin effect losses?.

thanks again.

kees

The relays are for the ON/OFF so they operate with the gun switch, i.e. every 10 seconds or so. The SCRs are for current control they operate 50 times a second. Relay contacts are more robust against high voltage sparking.
Copper strip for 50 HZ welders? and litz for inverters (20 KHZ+)?
Frank

chuckey said:

The relays are for the ON/OFF so they operate with the gun switch, i.e. every 10 seconds or so. The SCRs are for current control they operate 50 times a second. Relay contacts are more robust against high voltage sparking.
Copper strip for 50 HZ welders? and litz for inverters (20 KHZ+)?
Frank

Click to expand...

Hi Frank

The copper strip are used for the 20kHz + inverters, I did see here somewhere, and use litz for primairy, my question was is copper strip
usable for inverters because of skin effect? that is whi litze is used right?.

I think copper strip for a 50 Hz transformer is not a bad idea because of fill factor.

SCR can be protected easely with a snubber network, this eat that voltage spark,
use of a high voltage triac or two thyristors helps also, I did read that most welders
with thyristor regulator do it primairy.


regards

kees

Have the transformer dissasembled, a hell of a job because of the epoxy, so make it hot and
do etc.

coil have not survive, to much epoxy.

At this point see if you can locate a scrap microwave oven and extract the Microwave Oven Transformer a.k.a. MOT (1500VA)

You can remove the secondary and rewind or use heavy magnet wire or copper foil and insulator to step up the current to whatever you need for many applications.

Some have done this with a few turns to get very high spot welds using tungsten tips. but for welding large secondary inductance is preferred. Meanwhile the primary is around 10 to 50 Henries.

But it will take some time to do the best job for AC welding, so its easier to buy one.
https://www.instructables.com/id/Making-an-ARC-Welder-Part-2-of-2/?ALLSTEPS
examples.
https://www.google.ca/search?q=mot+...elder&rls=org.mozilla:en-US:official&tbm=isch

Also warning epoxy fumes are not healthy.

Hi Thanks

Yes I do now about the microwaves, I have however a 30 KVA core now and use them, otherwise all my work is for nothing,

I use them for a Co2 dc welder.

regards

kees52 said:

Hi Thanks

Yes I do now about the microwaves, I have however a 30 KVA core now and use them, otherwise all my work is for nothing,

I use them for a Co2 dc welder.

regards

Click to expand...

Well 30Kva is more 3.5 Kva, my mistake a typo.

Oke, I have search about how to calculate a transformer who is capable of 140 ampere 30 % duty.

software says core van 4.2Kva so this is not problem, however when I calculate a transformer
31 volts 130 amp I presume this is for 31 volts, but when I weld it is short circuited, almost.

then that trafo booms for shure the breaker.

How do we do this, how do we calculate it, just do 140 amp and 21.5 volts like the welder

usermanual say?

Not much to find on the internet.



regards

kees