I have a few, new, big ol' SCR's in the junkbox. What's the power rating of the welder? And is the thyristor on the primary side of the transformer (usual)?

Hi,

It's a 220 volt single phase unit, with an input fuse rating of

25 amps. Since there's not much more to the unit, I assume that

all of those amps' are for the welding jaws.

thanks

Russ

There's two kinds of spot welders. One uses a large inductor to limit current and drop the weld voltage, and the other uses a transformer to step voltage down and current up. I have never seen a spot welder with transformer control the secondary current, as it is much easier (cheaper??) to make a high voltage/low current thyristor than it is to make a low voltage/high current one.

Assuming that the weld voltage is around 25 volts, if it's a transformer type, any thyristor in the secondary circuit would have to handle 220 A, which would be a hockey puck style of thyristor and not a stud mount, so we can assume that it's controlling the primary side, meaning that it would only have to handle around 25 Amps.

I have a few SCR's rated for over 25 amps, but if the one you have is a TRIAC, then they won't do you any good. Let's see if we can investigate a little further.

The "thyristor" could also be a gate turn-off device controlled by a timer. Would you happen to know the manufacturer of the welder? Model number?

From your description you have a small portable spot welder with a max input of 25amp at 220Volts.

The control semiconductor will be in the primary winding of the transformer. This will be a Triac not an thyristor [ scr ]. the rating of the triac must be at least roundabout double the max rating of the welder, as such a 40 amp 600volt triac would be suitable, considering the one you have has blown it is probably underrated in either voltage or current or both. you don't have to fit a stud type here is a link to an isolated base triac which can be mounted on any metalwork that is convenient. It is a BTA41-600B

http://www.datasheetcatalog.org/datasheet/stmicroelectronics/7469.pdf

Dear RussBassani,

It may be around 10A. My advice is: check the circuit and take approximate current & voltage then replace with higher rating device of very low Trr.

Hello RussBassani: Your ref # just happens to be the same as a whole lot of print cartridges! So after trying a lot of different searches, I searched for T)-48 stud. And it brought up these two items. Whether they are what you are looking for I do not know. I am still looking, but, tell me what you think of these please? These are from: http://www.alibaba.com/product-gs/219874967/triac_thyristor_stud_version.html http://www.alibaba.com/product-gs/217695191/thyristor_stud_version_SCR.html

thyristor stud version,SCR

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triac thyristor stud version TO-48 case, also have fast thyristor, triac. Min. Order: 500 Piece/Pieces. thyristor stud version,SCR, Russia type. Russia type, stud version thyristor ...
www.alibaba.com/product-gs/219874967/triac_thyristor_stud_version.html - 54k - Cached - Similar pages -
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triac thyristor stud version

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thyristor stud version,SCR

TO-48 case, also have fast thyristor, triac. Features High surge current capability Stud cathode and stud anode version.
www.alibaba.com/product-gs/217695191/thyristor_stud_version_SCR.html - 53k - Cached - Similar pages -

If you scroll down the page you will see other stud fitting thyristors. I do not know your machine or the amp. So let me know if you find anything here. There is a dozen or so choices I think. If these are ok go to the site and have a chat OK? You did not say where you are?If I know you are in the US are you able to get stuff from China? I have just noticed there is a minimum order quantity. But if you talk to them nicely you never know?........I am still looking, Tell me where you are.

Let me know anyway..............

Take care......................

Hello RussBassani:

If the case or machine has not been repainted, can you tell me the colour and maybe post a picture?

Hello RussBassani:

Just found these links to what maybe what you want.

I think these are India and western rather than Chinese.

And it appears there is more choice.

http://www.google.com/search?hl=en&q=thyristor+stud+version&btnG=Google+Search

Let me know how you get on please, OK?

Take care, .........................

Russ,

Don't know if they are still in business, but Mars and Newark Electronics were sources I used for years to find just about any electronics.

Hello RussBassani:

The lists below are from PCI. I know they are the correct type but it seems yours has been discontinued/ I followed the thread to T0-48, that was as near as I could get. If you go to this site, and click on the 'Date Sheet', you will see a detailed thyristor with a schematic and ref' to the different parts.

I know yours is ¼-28 UNF-2A 15mm. And is buil;t to standard ISO 9002. If you run through the 5 other choices you may fin one that has the angle you need and the voltage/ amps.

I will leave it the for the moment.

It would help a lot if you can tell me from which country you want your thyristor. You may not have much choice as it is quite a small tip. If you can manage with either the Chinese one or another ½ Thread, which means getting your stud altered to half inch, it may help? I know it has been discontinued in one company but, another one may make it?

Phase Control SCR ThyristorsPSI has a wide variety of high power thyristors. All of our thyristors are produced according to ISO 9002 manufacturing procedures to ensure product consistency and all of our modules are CE approved.

Take care....................

As the part No you have given does not give any results, you need to specify the current and voltage rating of your machine, and where the thyristor is situated and what part of the circuit it is controlling. otherwise all the posters on this topic are just giving you general information which will not answer your question.

There are many types available many of which could be suitable for your machine but without some specific information I could not recommend anything.

from your rough description, it must be rectifier part. easy. try to find or buy one with greater than 500V (or 800v)/ 20A(or 30A, almost same price). enough.

cheap.

only pay attention to it troggle voltage and current. dont use too sensitive one. 1 or 1.2v/ 40mA (or 80mA) enough.

Hello RussBassani:

I assume as you have given extra info' that the sites I found are not any use?

If it is a spot welder head that this controls they are 'disposable' and renewable parts. It sounds like you have an old machine. You say you cannot see the makes of the Thyristor.

But can you tell us the make of the machine and if it has boon modifies please?

But can you tell us the make of the machine and if it has boon modifies please?

Please read 'been'.

We are the manufacture and stockist of the IC, IGBT,GTR,Thyristor,Power module ,Rectifier Bridge Modules with Mitsubishi,Fuji,Eupec,Toshiba,Omron ,Siemens,Semikron,ABB ,Westcode,IR Brand...

so I think I can help you with this thyristor,pls contact me :cnsales@yaspro.com.cn