Ceengland
Joined: 11 Oct 2020
Posts: 391
Location: MS
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 Posted: Wed Jan 20, 2021 7:34 pm Post subject: Z101B Aux Alternator and Overvoltage protection |
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On 1/20/2021 8:36 PM, Patrick Nelson wrote:
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For those with Z101B, what is your procedure for using the aux alternator? My initial thought was to turn on the aux alternator with the main alternator and use a lower voltage setpoint for the aux regulator. This allows the aux alternator to take over without intervention if the main alternator fails.
This causes a different problem, however. The main regulator could fail resulting in an overvoltage condition. The crowbar overvoltage protection circuits would blow the aux alt fuse and trip the main field circuit breaker. Z101B shows the aux alt fuse forward of the firewall so it can't be replaced in flight. Essentially, an overvoltage event on the main regulator will take out both alternators.
The solutions I can think of are:
* Enable the aux alternator only in case of main alternator failure.
* Move the aux field breaker/fuse to the main bus so it can be in the cabin, but this removes some fault tolerance of the design.
* Come up with an arrangement for the aux regulator that allows a slightly longer period before the overvoltage protection activates. This seems like a fragile solution though.
Note: My aux alternator is a BC410 with an LR3C regulator.
Interested in hearing people's procedures for the aux alt switch and/or if they've deviated from the Z101B wiring diagram to solve this problem
Thanks!
-Patrick
IIRC, the B&C regulator that's made for the backup alt is supposed to
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ignore an OV event caused by the main alt, and not react to OV except
from its own alt.
Protection for the B-lead would be the same whether the fuse (or
breaker) is on the fat wire tie point, or on a bus. The fuse/CB is
protecting the wire from the battery; not the alternator.
Charlie
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Charlie |
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