[SOLVED] Why are we still using SCR (Thyristor) for rectifiers ?

[Hatimoooo]

Hello everyone!
I'm wondering why are Thyristor/SCR still used as rectifiers ?
Why not using other switches such as IGBT, MOSFET ...

My application is 2.5 kW 48Vdc output characteristics for a 400Vac 50 Hz input

Thanks

 

[ArNvC]

Only advantage of SCR is that it has high reverse voltage blocking capability...otherwise it is really a slow device. Also, thyristors has “latch” on state that is once they begin to conduct and remain on after the gate pulse is removed until they are commutated. This characteristic is used to advantage is some circuits, but is not always an advantage.

 

[Hatimoooo]

Thanks for your answer.
That means that if you have low voltage rectifier, Thyristor is just a problem not a solution
But I can still find 200V thyristors

 

[Orson Cart]

SCR's (thyristors) are still used in ultra high reliability rectifers (yes even 48VDC, from 10 to 10,000 amps) as they have the fewest parts, no EMC concerns, and a simple analog circuit can perform all the control - also earth shielding in the transformer stops a lot of CM impulses getting through to the secondary - also they can have overload capability (e.g. 200% for 30 mins)

Using 800V or 1.2kV SCR's (on the o/p side) means it is unlikely they will ever fail due to mains spikes.

It is possible to create a unit with a 15 year full power lifetime (with suitable electrolytic caps) and there are examples in the field that have lasted 20+ years,

usually it is the control circuits that cause the ultimte demise (especially so with uP controllers).

Hopefully the above answers your questions.

p.s. on the green front, the iron and copper used (and Al heatsinks) can be completely and easily recycled on an SCR converter.

Also the efficiency is quite good and can often be around the 92% level, 95% for low loss 50/60Hz transformers.

 

[Hatimoooo]

I think the reliability and overload capability are the main advantages.
Thanks a lot for your answer, it helped a lot!

 

[Powerfreak]

Hi,
"reliability" is the first, "ruggedness" the second and "price" the third of the 3 most important facts to use SCRs.
Currently I have built a 30kVA switch... with SCR... IGBTs or other switchable silicon would double the price...

 

[ArNvC]

Yep, cost is another criterion...SCR is cheap.

 

[Hatimoooo]

Hello again.
I think the price is not a good criterion when dealing with low power devices (3 kVA for example which represents my case).
Thank you so much for your answers and most importantly your experience advices
Thanks again and I will mark this as solved!