nuckolls.bob(at)cox.net
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 Posted: Sun Jul 13, 2008 4:59 pm Post subject: FYI: Dancing ammeter . . . Generators can do it too! |
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I recently had occasion to converse with Concorde Battery about
several cases of "dancing ammeters" on older airplanes that were
fitted with generators and recently retrofitted with RG batteries.
The change in battery internal resistance seemed to have triggered
the events.
Back in '04 we had a discussion the problem as it related to
a negative resistance effect that occurs in alternator/regulator
combinations where VOLTAGE SENSE and FIELD POWER share the same
conductor. See:
http://tinyurl.com/5pee5j
This can happen in systems that use the "generic ford" regulators.
Zeftronics speaks to the phenomenon in their R15V00 data sheet:
http://www.aeroelectric.com/Mfgr_Data/Regulators/Zeftronics/R15V00_Ford_Style_Reulator.pdf
Seems the same thing can and does happen in generator systems
even when they use the old electro-mechanical regulators. In the
case of the Concorde Battery substitution, increased path
resistance in the Vsense/Field_Supply lead was root cause . . .
changing the battery only added the final stress that
tripped the system.
Renewing all components (breaker, switches, connectors, etc)
in the subject power path fixes the problem for another 20+
years.
Any time you see the dancing ammeter phenomenon in any airplane,
be sure to refer the owner to the "dancing ammeter" discussion
on the List.
Bob . . .
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( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
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