RE: Re: [Development] Lights functions required

["Mick Furlong" <dorsai@xxxxxxx>]

>
>
> > I am probably talking drivel but how about some form of mcb?
> >
>
> Your not talking drivel, but even the fast versions of the MCB will
perhaps
> not be fast enough. I quote from the SSR handbook
>
> " Mechanical circuit breakers ore generally too slow to prevent
damage to
> semiconductor devices, barely fast enough to protect printed circuitry
and
> wiring from high short-circuit currents. Standard cartridge fuses are
two
> slow to protect semiconductors when operating close to their maximum
> ratings. However, they can be successfully used if the semiconductor
is
> severely derated to accommodate a lower value fuse..."
>
> There are some very fast fuses called semiconductor fuses, which blow
very
> fast and limit the current, but you have guessed it they are more
expensive
> than the triac.
>
> The same book also lists a example of a 25A device, its operating
range:-
>
> 100A for 1.00  second
> 130A for 0.10  second
> 250A for 0.01  second
> 725A for 0.001 second
>
> This example is a SSR which are much harder than a simple TRIAC
>
Is there any way to calculate if the MCBs would be fast enough? Seems to me
that even if they are more expensive a lot of people(well me anyway;) would
prefer a low maintenence solution with minimal items needing replacement.

Mick




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