RE: Re: [Development] Lights functions required

["Keith Doxey" <ukha@xxxxxxx>]

MCB's are much more expensive and you need to upgrade the triac to at least
40A or 60A capability. Those size triacs have different cases and would not
fit inside an X10 module.

X10 are build down to a price (then quadrupled for the UK) rather than
designed for long reliable service. Its a price/features trade off. :-(

Keith

-----Original Message-----
From: Mick Furlong [mailto:dorsai@xxxxxxx]
Sent: 13 June 2001 14:13
To: ukha_d@xxxxxxx
Subject: RE: [ukha_d] Re: [Development] Lights functions required


>
>
> > 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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