Inverter grade scr vs. phase control scr 2

[electromike]

I would like to know what electrical parameters make the difference between a inverter grade thyrister and a phase control thyrister? I am tring to cross refrence an old obsolete inverter grade thyrister in an attemp to make a quick repair to a UPS system at my facility that has a shorted scr in the ocillator.

 

[jraef]

"Phase control" is a firing technique used for voltage control using thyristors, it has nothing to do with the "grade" of the devices. I've never hear the term "inverter grade" as a standard for the industry either.

Basically, if you can, look up the performance specs for the SCR you have and match them. If you don't have data sheets, get hold of a decent thyristor supplier, like Westcode, and give them the situation, they will have a solution for you I'm sure.

"Will work for (the memory of) salami"

 

[electromike]

jraef, I got the "invertere grade" from a Powerex rep. when I give him the device numbers. My experience is with DC motor drives and I know what a phase control thyrister is but the inverter grade stuff was new to me too.

 

[Skogsgurra]

There is actually a rather big difference between phase control SCRs and inverter SCRs.

Phase control isn't critical when it comes to turn-off time. The commutation takes place sooner or later anyhow.

In an inverter application (yes, there were VFDs with thyristors once upon a time), the turn off time is critical. So you need fast turn off thyristors. That is where the term "inverter grade" comes in.

But, today? You don't build VFDs with thyristors in the inverter part - do you? No, not really. Unless you are building induction heaters, cycloconverters or CSI. Especially the induction heaters working with 400 Hz and more need fast turn off thyristors.

Is your application induction heating/welding or something similar?

http://www.google.se/url?sa=t&rct=j&q=&esrc=s&source=web&cd=7&ved=0CHcQFjAG&url=http://

http://www.westcode.com/publicity/p...zjbL3ykh4X2koYg&bvm=bv.49641647,d.bGE&cad=rja

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[electromike]

Gunnar, the aplication is for a UPS inverter. The link you provided was very helpful. Thanks.

 

[jraef]

Gunnar,
So you are saying that "inverter grade" is the new name for GTO thyristors then? That would have made it much more clear to an old fart like me. Clever marketing if so, because GTOs got a bad rep a few years ago when transistor drives railed against them in the early days. It was not not deserved, it was just negative selling, but it happened nonetheless. So it sounds like the mfrs have "reinvented" the product by giving it a new moniker.

"Will work for (the memory of) salami"

 

[ScottyUK]

Jeff,

No, it's not a GTO. Inverter-grade thyristors are much the same four-layer device as a regular thyristor but with a different gate geometry which allows it to quickly regain blocking capability. Some discussion from Westcode in this document.

http://www.westcode.com/publicity/present/prod_pres.pdf

 

[jraef]

Ok, never mind me as I try driving on my learners permit...

"Will work for (the memory of) salami"

 

[electricuwe]

Inverter grade thyrsitors or fast thyrsitors have been the workhorses of high power inverters before the advent of the bipolar darlington modules and the GTO. Even these parts have now been replaced by IGBTs. Therefore your UPS seems to be some quite old equipment. Consider donating it to a museum instead of repairing it. You really can be lucky that your equipment lasted that long.

As the newer devices came up at low power first, smaller ratings of fast thyristors ( up to 100 A, up to 1800 V) were replaced first in applications like UPS and hence the semiconductor suppliers discontinued the components approx. 20 years ago. The higher rating followed as soon as higher rated IGBTs and GTOs were available and widely accepted.

The only application were fast thyristors are still used today is high power induction heating at moderate frequency and beside spare part business this is the only market for these parts today. Westcode / IXYS is the only major supplier still active in the business.

If you can post the type designation and/ or a photo I might be able to support you in finding a replacement part, if you really want to repair.

 

[electromike]

I was able to locate Wescode C385P SCRs from a supplier. We now have the inverter running but this is only until this inverter gets retrofitted with IGBTs by the OEM or we buy a new one. Hopefully certain people will learn that paint that is still glossy in not the only metric for figuring usefull service life remaining on equipment! Thanks for all the input.