<...All charging systems should have protection for
this. Don't you? ...>
Yes.  I've described it in some detail, about three
times so far, on this thread.  Now, the scenario of a "... load dump
where the battery is disconnected ..." (and presumably all of the
aircraft systems (can't see 100V with any load AT ALL - if then)) happening
simultaneously with regulator failure to full output ...  would be ...
???

PVORT for three days now :o) ... Jim S.


Michael LaFleur wrote:

>In the case of a load dump, where the battery is
>disconnected for a charging circuit, you will see
more
>than 100 volts.
>
>The alternator, being low impedance will cause
large
>positive transients. Simultabeously, the collapsing
>field will cause negative field decay transients.
>These can and will be in excess of 100 volts. All
>charging systems should have protection for this.
>Don't you?
>
>--- Jim Sower <canarder@frontiernet.net> wrote:
>
>  >
>>Finn Lassen wrote:
>>
>>    >>
>>>I think the +100 volts statement relates to no
>>>      >>>
>>battery load.  Have you >>    >>
>>>/anyone actually /seen/ that happen?  I guess if
>>>      >>>
>>the electrical system >>    >>
>>>was designed so that a contactor could disconnect
>>>      >>>
>>the battery from the >>    >>
>>>load circuits and the load circuits (avionics)
>>>      >>>
>>still be connected to >>    >>
>>>the alternator you would have a situation where
>>>      >>>
>>you could wave your >>    >>
>>>avionics goodbye.
>>>Perhaps.  But that wouldn't be very clever. >>>      >>>
>>Anyone who designed his >>    >>
>>>system to protect his avionics from a Battery
over
>>>      >>>
>>voltage and ignored >>    >>
>>>the Alternator deserves whatever happens.
>>>Let's say on top of that that one (or all) of the
>>>      >>>
>>three retifiers >>    >>
>>>shorted out too, you'd have 100 volts A/C into
>>>      >>>
>>your avionics. Not a >>    >>
>>>pretty picture. (I've seen Zener diodes short out
>>>      >>>
>>regularily due to >>    >>
>>>overload/voltage; rectifier diodes usually fail
>>>      >>>
>>open - but not >>    >>
>>>always).   We're stretching a bit here aren't we?

>>>      >>>
>>Back to the 100 V >>    >>
>>>that we've already agreed can't happen, shorted
>>>      >>>
>>diodes causing AC >>    >>
>>>(which I'm not at all sure can happen), all three
>>>      >>>
>>rectifiers (that's >>    >>
>>>all SIX diodes shorting at the same time (none of
>>>      >>>
>>them failing open >>    >>
>>>which is more common), zener failing, etc.  If a
>>>      >>>
>>diode fails every >>    >>
>>>1000 hrs, the whole bank failing would happen
>>>      >>>
>>every 1000^6 hours.  >>    >>
>>>That's a one with TWENTY ONE zeros behind it.
>>>      >>>
>>I think I can live with that ... Jim S.
>>
>>    >>
>>>Finn
>>>
>>>Jim Sower wrote:
>>>
>>>      >>>
>>>><... the alternator is capable of producing over
>>>>        >>>>
>>100 volts ...>
>>    >>
>>>>I don't think so ...
>>>>...
>>>>Bottom line, with the regulator failed (or
>>>>        >>>>
>>bypassed) to send full B+ >>    >>
>>>>voltage to the field, the charging voltage never
>>>>        >>>>
>>exceed 18V in my >>    >>
>>>>experience.
>>>>        >>>>
>>>
>>>
>>>-- >>>Homepage:  http://www.flyrotary.com/
>>>Archive and UnSub:  >>>      >>>
>>http://mail.lancaironline.net/lists/flyrotary/
>>    >>
>>>      >>>
>
>
>--
>Homepage:  http://www.flyrotary.com/
>Archive and UnSub:  http://mail.lancaironline.net/lists/flyrotary/
>
>