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[Clarence L.Snyder]

Ernst Denbroeder wrote:
> 
> > >That's a good question.  How do they PWM the coolant fans? I know I
> > >can hear the relay clicking away..
> > >Shannen
> >
> > I believe it's (the actual switching) done with an SCR, but that is coming
> > from a total klutz in terms of electronics.
> >
>         Close... :)  SCR's are used for AC applications.  An SCR relys on
> the 0V crossing to turn off.  And a TRIAC is two SCR's in parallel (sort
> of).  :)
> 
>         Ernst.
Also used (with commutation circuit) on DC controllers like the GE EV1
motor controller used on forklifts and some electric cars. REAL tricky
getting the suckers to turn off though!