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Basically, yes, I don't feel that you have to worry about high altitude,
corona initiated arcs.  In general I would be careful to be sure that BEMF
collapse is prevented.  This amounts to being sure that a load always exists
on the output of the alternator.  For instance opening the master relay could
unload the alternator completely in some configurations.  The best solution
would be to have a 25 to 50V (on 12 V systems) MOV directly from the field and
output terminals to ground (frame).  This is good practice anyway to protect
the avionics.  As I recall, specifications for car electronics plan on 50 to
60 V spikes, in lieu of the use of MOV’s.

As previously discussed though, there may be problems with the brushes
"dusting."  Carbon dust can complete a low voltage path and thereby initiate a
low voltage arc that has absolutely nothing to do with altitude.  Why and if
brushes act worse in (high altitude) service will have to be answered by
someone else.


Robert Smiley wrote:

> In plain language, are you saying we do not need to worry about electrical
> arcs in auto -mitsubishi alternators below 18,000 MSL?

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