Author Topic: Arc welder triac controler (Read 60598 times)

oldway · « **Reply #50 on:** September 21, 2015, 08:20:14 am »

Why the current control solution by movable magnetic shunt is better than by a triac controller?

For ease of starting arc, welding transformer must have the highest possible no load voltage.
It takes at least 50V and good welding transformers have a no load voltage of 80V.

The current adjustment by magnetic shunt does not change the open circuit voltage, while the triac controller decreases the primary voltage, and therefore also that of the secondary.

Furthermore, ajustement by magnetic shunt change the output regulation curve of the transformer, making it steeper at low current.
That's a great benefice for stability of the arc at low current settings.

Internet is full of supposedly miraculous solutions: car running with water, devices with 100% or higher eficiency, miraculous electrolysis through the vibration of water molecules, battery regeneration with devices of a few watts, ... and so on .. .

These miraculous "inventions" are contrary to the basic laws of physics and electricity and are coming from two sources:
- either they were created by people who know nothing and who believe, in good faith, to have invented the wheel.
- either they are created by crooks who want to earn a lot of money by exploiting the gullibility of people who are not specialists in the field.

So pay attention to what you find on the Internet, there is good information, but also technical and scientific nonsense.

eneuro · « **Reply #51 on:** September 21, 2015, 04:54:13 pm »

Quote from: oldway on September 21, 2015, 08:20:14 am

The current adjustment by magnetic shunt does not change the open circuit voltage, while the triac controller decreases the primary voltage, and therefore also that of the secondary.

When we replace HV coil with something desired for high current, not too much space left for oryginal MOT magnetic shunts, so probably I'll try to make this tricky additinal magnetic circuit on top of this thing

Anyway, during testing my new upgraded (spot) welder software, I forgot change current limit set for testing in mains Hall current sensor configuration and left it at.. 0.5A RMS level

and I've almost rewritten turn on/off button software averaging and contoll, since... software was good for button event processing and starting transformer SCR's, but of course inrush currents were much bigger than 0.5A rms (100ms), so when I had no idea howto write better MPU pin interface, after a few hours of

and debuging, I've found this bloody definition which puzzled me for so long time

Code: [Select]

#define FUSE_CURSEN_LIMIT (0.5)
Beauty of software development - one line of code can ruin your day or let magic to happen other time

Yep, using phase controll to limit output current can degrade voltage, too, but in my case It shouldn't be a problem- I'll have HV high frequency pulses in series with welder transformer.

However, phase shift control can be very usefull for demagnetization of transformer core and developing such soft start code for my ATTiny85 MPU right now

oldway · « **Reply #52 on:** September 21, 2015, 05:31:26 pm »

I still not understand what spot welder has to do in a topic about ARC welder !
But anyway,
- it is stupid to use a wire with such an isolation for more than 1000V in a secondary coil of few volts.
It is also very bad for power dissipation.
Use enameled wire and you will have plenty of space to place the original magnetics shunts again.
You may also use several wires in // if necessary.
- So far I remember, spot welding transformers were not fase controlled, but time controlled.
Thyristors (2 in anti-paralel for better dV/dt than triacs) were full conducting during a variable number of complete sine waves, this number depending on the desired current.
- MOT is not enough powerfull to make any serious spot welder. (800 to 1100W, or 1000VA to 1375 VA) (need 10 times more)

eneuro · « **Reply #53 on:** September 21, 2015, 08:32:58 pm »

Quote from: oldway on September 21, 2015, 05:31:26 pm

I still not understand what spot welder has to do in a topic about ARC welder !

Both (spot) welder share huge amount of the same software code, use the similar hardware (additional custom windings for spot welder), both use the same Hall effect current sensor, both are controlled using one smart button, which allows multiply wedling time from 20ms up to 10 minutes (connected with remote RF controll in next upgrade, when my home automation project is finished).
Only small diferencies how (spot) welding process is started and finished with optional phase shift control and HV circuit for arc welder

BTW: We'd like to see some photos of OPs MOTs setup, because a few images are worth thousands of words...and always interesting to see how it was made

oldway · « **Reply #54 on:** September 22, 2015, 07:34:36 am »

Absolutely nonsense

A spot welder of such a low power does not even have to be phase controlled nor need a Hall effect current sensor because you do'nt need to know what's the current. (and furthermore, I already explain to you that using a CT is far more reliable and stable than an Hall effect current sensor).
All what it need is a timer and a solid state relay...

As I said, technologies of MMA welding and of spot welding are fully different...nothing in commun.

eneuro · « **Reply #55 on:** September 22, 2015, 07:57:45 am »

Quote from: oldway on September 22, 2015, 07:34:36 am

A spot welder of such a low power does not even have to be phase controlled nor need a Hall effect current sensor because you do'nt need to know what's the current.

I didn't said it have to be (many commercial available spot welders have only controll of amount of full wave pulses) , but it is neat feature I wanted to have, since I might want to use its output as high current power source, but with controlable output power, so I've did it, because of ... I can

I will post photos of my welding machine when upgrade is finished and it looks much better than many "commercial" available and have features I wanted to have at high power (I mean a few kW) low voltage output

BTW: My (spot) welder is not based on any MOT, but bulky transformer and it has thick copper in his primary/secondary winndings, not China aluminium wires plated with copper, which I've found in MOT I've posted a few posts above

Yep, I've MOT too, so the same software recompiled for this smaller spot welder/solder iron heater will do other less demanding tasks, but not too much changes in source code needed...

oldway · « **Reply #56 on:** September 22, 2015, 08:16:24 am »

Why do you invade this topic with your spot welder project?

You can not open a new topic?

Once again, I repeat, this has nothing to do with an arc welder and rodrigopires phase controller does not even have any µc ...

No need of "huge amount of software code".

eneuro · « **Reply #57 on:** September 22, 2015, 11:37:12 am »

Quote from: oldway on September 22, 2015, 08:16:24 am

Once again, I repeat, this has nothing to do with an arc welder and rodrigopires phase controller does not even have any µc ...

He might quicly realize, that this simply phase controller is too simple, and galvanic insulated small DIP 8 pin ATTiny85 MPU can help automate welding and do many other things for him, however it will be as smart as its programmer is

Try to make such (spot) wedling possible, using ...foot pedal

oldway · « **Reply #58 on:** September 22, 2015, 12:41:56 pm »

Quote from: eneuro on September 22, 2015, 11:37:12 am

He might quicly realize, that this simply phase controller is too simple, and galvanic insulated small DIP 8 pin ATTiny85 MPU can help automate welding and do many other things for him, however it will be as smart as its programmer is

Then, why don't you share yours schematics and software with rodrigopires ?

Quote

Try to make such (spot) wedling possible, using ...foot pedal

That's not SPOT welding ! This is resistance seam welding.

This is a spot welding machine with foot pedal.
I already used one in the past.

And an another one.

rodrigopires · « **Reply #59 on:** November 26, 2015, 09:21:52 pm »

Hi, sorry for the long wait but i have been really busy, anyway, here is my final unit!

oldway · « **Reply #60 on:** November 27, 2015, 09:39:29 am »

With resistive load (incandescent bulb) every schematic of dimmer works well, even far more simple schematic.

But with highly inductive load as a welding transformer, there are a lot of troubles.

If there is any asymetrical triggering of the triac, the transformer will saturate and a very high current will flow throught the primary winding, with magic smoke and / or trip of the circuit breaker.
One of the greatest weakeness of this simple schematic is that the pulses are very short, only 2 or 3µs.
With highly inductive load, this it not enough to ensure that current reach the value of the holding current at the end of the triggering pulse and the triac can loose the conduction.
Even worse, the + and - holding currents are not exactly the same, so triac can trigger during one alternance and not during the other, saturating the transformer.

It would be very important to verify with an oscilloscope if this trigger circuit is really generating a pulse train.
But for doing this, you will need a diferential probe or to feed the dimmer and load with an isolation transformer.

In every case, don't try to dim your welding transformer without a resistive load in parallel with the primary. (your incandescent bulb)

aburastas · « **Reply #61 on:** November 29, 2015, 12:32:32 pm »

Hi... New to the thread but since I had followed all the mesaages I think that the part number of the transient suppresor is for the unidirectional part but in the circuit the bidirecciital type is needed. The part number that end in 68CA not 68A.

Anyway very interested if rodrigo managed to use the welding machine with this controller... Waiting for results

oldway · « **Reply #62 on:** November 29, 2015, 03:06:28 pm »

I have used a bridge rectifier with 4 zener diodes (15V 1W) in serie instead of this transient suppressor.
So I am sure that it is perfectly symetrical.

oldway · « **Reply #63 on:** November 29, 2015, 06:47:48 pm »

Use the two ac terminals of the rectifier bridge in place of the terminals of voltage supressor and the four zener diodes connected between + and - polarities of the bridge...(the 4 zener diodes connected in series, with the correct polarities, of course)

aburastas · « **Reply #64 on:** November 29, 2015, 07:05:02 pm »

Yes... I deleted the post when I understand what you want to say.... I was confused with the diode bridge... I belive that was refering to the one in the schematic... Any way the datasheets says that tvs are much better in time response and watts capabilities... The only critical point is to get the bidirectional part. 1.5KE68CA But.. Perhaps it isn't so critical in this schematic..

oldway · « **Reply #65 on:** November 29, 2015, 08:46:32 pm »

It is very critical with highly inductive load ...if there is any asymmetry, transformer will saturate and a high current will flow in the primary.
Even diac is a problem as it is not fully symmetrical.
Philips as used diac in only one direction also with bridge rectifier to be sure there is no asymmetry.

About "better in time response", no problem at all, it only works at 50 or 60 Hz.
Power dissipation of the four zener diodes is 4W, it is enough.

aburastas · « **Reply #66 on:** November 30, 2015, 09:25:40 am »

Well... I know that my english can be... "funny?" jajaja but seem that we can understand us.. Following your advices I think in this way of chop the ac signal... In a "old way" without programing with the 555. Trying to first, make the trigger pulse longer with the astable oscilator and second, make that all components run always in the same direction with your brige rectifier technique... Is only a general idea... What do you think about? Can be functional? Since rodrigo seem has abandoned us.... I hope he hasn't electrocuted...

oldway · « **Reply #67 on:** November 30, 2015, 02:28:37 pm »

Dirty-cad ?

aburastas · « **Reply #68 on:** November 30, 2015, 02:55:42 pm »

Very good the emoticon... It's a freehand analogic sketch jajaja

oldway · « **Reply #69 on:** November 30, 2015, 03:58:33 pm »

Quote from: aburastas on November 30, 2015, 02:55:42 pm

Very good the emoticon... It's a freehand analogic sketch jajaja

Even so, you could do better...you are only showing us that you don't care !

rodrigopires · « **Reply #70 on:** November 30, 2015, 05:31:59 pm »

thanks for all the support on my project, i will make a more accurate video of testing the controller, with the two transformer and the resistive load (light bulb). i should have it done by the end of the week.

rodrigopires · « **Reply #71 on:** November 30, 2015, 05:46:28 pm »

Quote from: aburastas on November 30, 2015, 09:25:40 am

Since rodrigo seem has abandoned us.... I hope he hasn't electrocuted...

sorry but i only found out today that the post has already a fifth page, so i was checking on the fourth and there was nothing there...

Still alive!

moya034 · « **Reply #72 on:** November 30, 2015, 05:57:08 pm »

Welding machine built from a car alternator:

https://web.archive.org/web/20130410190142/http://myweb.cableone.net/rschell/TIG.htm

oldway · « **Reply #73 on:** November 30, 2015, 06:16:40 pm »

Quote from: moya034 on November 30, 2015, 05:57:08 pm

Welding machine built from a car alternator:

https://web.archive.org/web/20130410190142/http://myweb.cableone.net/rschell/TIG.htm

Only for TIG welding, MMA need a higher voltage.
It is non sense, you need expansive alternator and motor: you can buy good MMA inverters for less than 100$...

moya034 · « **Reply #74 on:** November 30, 2015, 06:21:22 pm »

Quote from: oldway on November 30, 2015, 06:16:40 pm

Quote from: moya034 on November 30, 2015, 05:57:08 pm
Welding machine built from a car alternator:

https://web.archive.org/web/20130410190142/http://myweb.cableone.net/rschell/TIG.htm
Only for TIG welding, MMA need a higher voltage.
It is non sense, you need expansive alternator and motor: you can buy good MMA inverters for less than 100$...

TIG and stick welding both use constant current power supplies, it will happily do either. That is a project meant for people that already have the parts around. Great idea if you install it in a vehicle, then you have a mobile welder powered by your truck engine


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Author Topic: Arc welder triac controler (Read 60598 times)

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