RE: Re: [Development] Lights functions required

["Dr John Tankard" <john@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

John





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