[Amps] thyristor controlled soft start?

jeff at wa1hco.net jeff at wa1hco.net
Fri Mar 21 13:36:16 EDT 2008


Out of curiosity, how does a zero crossing solid state relay work?  I had
thought it had a triac inside, but your comment about voltage drop makes
me question that assumption.

jeff, wa1hco

> Hi Andy,
>   Are you thinking about just replacing the relay
> across the resistor with a Triac?  Or something more
> involved like a phase controlled ramp??
>
>   A Triac will exhibit a considerable loss during
> normal, post startup, operation.  I've seen circuits
> where a Triac is used with a relay connected in
> parallel.  The Triac is first enabled, then shorted by
> the relay.  This greatly reduces contact wear on the
> relay while avoiding the typical 2V drop of a Triac.
>
> 73 & Good morning,
>   Marv WC6W






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