Beemer
Joined: 26 Aug 2006
Posts: 87
Location: Middle Georgia
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 Posted: Tue Nov 04, 2008 2:13 pm Post subject: ANL current limiter location on rear battery installations |
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| Quote: | > That interested me since in another context I had been wondering about ANL location. I was
puzzling why in Z-24 the ANL was shown downstream of the internally regulated alternator
isolation contactor. My thinking was that by having it close to the alternator it would blow if
anything (including the isolation contactor) ran amok downstream. What is the advantage of
having it at the main bus end ?
A The ANL limiter (fat fuse) is there to protect the alternator b-lead wire . . . the source of
energy that places this wire at risk is NOT the alternator but the battery. An alternator is
incapable of putting out enough current to open its own b-lead protection while the battery is
capable of fat-wire faults approaching 1000 amps. So, while selecting the SIZE of the protection
device is driven by alternator output capability, selecting LOCATION is associated with the risk
source . . the BATTERY.
On some occasions, we have fat wires that can source a fault from either end . . . in
which case, you might have a limiter at both ends of the same conductor. However, I've never
encountered a situation like this for small aircraft. Bob . . . |
The above is in the FAQ's for the list. I would like to clarify a bit further: If the battery is the current feeder in a frayed B-lead scenario, and the battery is in the tail (with the master contactor and eng power bus (FI auto)), then wouldn't the ANL current limiter be located back there as well? If so, between the battery and contactor, or between the contactor and main bus loads?
My situation seems to dictate a current limiter on both ends of the B-lead...
Thanks,
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_________________
Beemer
KF2 (and now an M3!)
Suzuki G10 three-banger
Middle Georgia |
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