Transorbs (formally Try this link)

[Bernd Felsche]

John Dammeyer tapped away at the keyboard with:

> 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?

Diodes fry due to over-voltage? Although I haven't seen the spec's
for the various types (possibly hundreds) of diodes used, my *guess*
is that they won't break down until they get at least 100V of
reverse voltage.

The alternator's control circuitry should protect against such an
over-voltage situation anyway by manipulating the excitation
current.  There's typically a Zener diode to sense over-voltage.
Such a circuit can react quickly enough to protect the rest of the
vehicle's electrics. Output voltage is typically limited to about 30
volts in a 12 volt electrical system. [ref Bosch Automotive Electrics/
Electronics]

> 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?

The alternator puts out a *current* many times that which can be
useful to a fuel pump. Unless you're in a competition vehicle and
have stripped out all but *essential* electrics.

It's not unusual to have an alternator produce in excess of 100A.
Fuel pumps seldom draw more than 8A in motor cars.

When the connection between battery and alternator fails, the
alternator's unsmoothed ripple voltage is seen by electrical
consumers. Note that most alternators supply at least 3 phases (6
diodes) and the resulting ripple is only a couple of volts; enough
to confuse ECUs, but hardly enough to cause damage to electrical
consumers designed for automotive use.

If you're looking at transsorbs to smooth the ripple, you should
probably be looking elsewhere for something more useful.
-- 
Bernd Felsche - Innovative Reckoning
Perth, Western Australia
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