From: "Michael A. Terrell"
Subject: Re: High DC current Transfer Switch
Date: Sat, 30 Nov 2002 20:27:55 -0500
Organization: Have you seen my bench? No, really! Where is it?
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Winfield Hill wrote:
> "Michael A. Terrell wrote...
> > Winfield Hill wrote:
> >> John Woodgate wrote...
> >>> A 10 000 A switch isn't electronics, it's civil engineering. (;-)
> >> Hmm, I wonder what a 10kA contactor looks like?
> >> Thanks,
> >> - Win
> > Just be glad its not in the next room while you're working.
> > It could shake things off your bench. :)
> I'm not sure. On one hand, the 600A contactor I used in a recent
> design was rather large, about 4 to 6-inches on a side IIRC. On
> the other hand, my 300V 6000A solid-state transfer switch used six
> large-sized hockey-puck TRIACs with Wakefield high-pressure-spring
> heat-sink clamps, and it wasn't _that_ large or impressive. While
> my 6000A pulse setup might not meet our O.P.'s continuous-operation
> requirement, neither did it use the largest devices available from
> Powerex, so it's likely a solid-state solution could serve well.
> You know, the stuff that modern locomotive-engine designers use.
> - Win
Solid state control is great, but for someone who has worked with
high power transmitters, hearing the contactor slam home lets you KNOW
all of the control and interlock circuits are working, without looking
around to take meter readings. Also, it is easier to troubleshoot
safety interlocks wired at 24 VAC, or higher than logic levels where
every switch runs back to a logic board. This is an important condition
when you just went off the air because a door switch is out of
alignment, or a wire has opened because someone moved a wiring harness
and it got nicked by the sheet metal. Big contactors in steel boxes
bolted to a 4' X 10' piece of 1/4" steel plate, and you can hear it
anywhere in the transmitter site. :)
Michael A. Terrell