Dual SCR vs single TRIAC to switch on Inductive load

[anishkgt]

What would be an ideal switch to control an Inductive load, Dual SCR or a single TRIAC ?

I was using TRIAC to switch a MOT at the peak of a sine wave. Then i read that some use Dual SCR's to control inductive load as that is how its done in an industrial environment. Can it be said Dual SCR design is the old way of controlling an ac load and TRIAC being bi-directional was the newer version to SCR's.

From a design perspective, a TRAIC uses less space and fewer components compared to a dual SCR design. Would that be all ?

[schmitt trigger]

SCRs would have fewer loses.

But most importantly, as they conduct in a single direction, they would not be re-triggered by high dI/dt

[Circlotron]

Triac should be good enough for a MOT provided you have good enough snubbing. SCRs have the advantage of greater tolerance to dv/dt as well as much greater surge current capability.

[anishkgt]

Thanks guys the dv/dt is a sure thing to bear in mind when the load is highly inductive. I guess then my design with the dual SCR would be correct.


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[Zero999]

The only disadvantage of SCRs is they don't trigger on all quadrants. The gate needs to be positive whilst the anode is positive.

[oldway]

Thanks guys the dv/dt is a sure thing to bear in mind when the load is highly inductive. I guess then my design with the dual SCR would be correct.


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This was true a few years ago, but with new developement and improvement of 3 quadrants (snubberless) triacs, it has changed.

The new technology snubberless triacs has high dv/dt, as high as scr's.

There is no reason to use dual scr, a single snubberless triac can do the same job with the same reliability and is easier to trigger  than dual scr's.

[anishkgt]

Yea snuberless was something that I had in mind as well but wasn't sure if I should stick with the old way or snuberless.


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[oldway]

For high power, the dual scr's solution is still preferred because limited range of 3 quadrants triacs.

https://www.google.be/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&ved=0ahUKEwj4it_g5s7VAhVEblAKHZEtB9kQFgg-MAM&url=http%3A%2F%2Fwww.aeg-ups.cz%2Fcz%2Fdownload%2F1404042748%2F%3Fat%3D1&usg=AFQjCNHyv24f9MEFgaNQnrhfY-9ZpGdVUw