Transorbs (formally Try this link)

[John Dammeyer]

Hi,

Brings up the question.  You stated the Transorb holds the voltage down
until breakers trip etc.  One of the Marine suppliers lists what looks
like a large transorb to prevent the load dump from damaging the
alternator diodes.  However they imply that the alternator can be run
continuously with the battery disconnected without damaging the
alternator diodes.

Certainly in an aircraft I'd hate to have the main breaker pop and lose
fuel pump etc. just because the voltage went high.

So I guess the question is how much current needs to come out of an
alternator running at full tilt to bring the open circuit voltage back
down to 'safe' levels?  I can see a couple of failure scenarios
happening here. (perhaps there are more).

1. Alternator wire breaks from alternator to battery and there is now no
load on alternator.  Normal situation here is alternator fries diodes
due to overvoltage.  Does High power transorb protect alternator until
aircraft or boat or car reaches home port?

2. Battery wire not properly connected to battery and battery becomes
disconnected.  Alternator and entire electrical system experience high
voltage.  Would not the fuel pump provide enough of a load to keep the
alternator voltage low enough or safety?  Would Transorb be any better?

Comments?

Regards,

John Dammeyer

> Date: Mon, 12 Jun 2000 21:51:32 -0700
> From: garwillis at msn.com (Garfield Willis)
> Subject: Re: Try this link
>
> On Mon, 12 Jun 2000 21:09:12 +0100, "Gavin"
> <gavston at sprockets.freeserve.co.uk> wrote:
>
> >just found this snippet of info on the web.  Not much good, but it
may be of
> >somegood to someone!!!
> >
> >http://www.tri-m.com/tech_pages/techpaper8.html
>
> Is this a thinly disguised troll? :)
>
> An important and useful topic, sadly somewhat mangled...
>
> The topic is "silicon avalanche diodes", commonly known as transorbs,
> used for protecting expensive/delicate circuitry from the harsh
> automotive environment.
>


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