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What to monitor in a dual alternator airplane

 
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nuckolls.bob(at)aeroelect
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PostPosted: Wed Sep 26, 2018 11:41 am    Post subject: What to monitor in a dual alternator airplane Reply with quote

Quote:
Glad I just happened across this then as it's not immediately apparent. Basing my design off Z-12 I had assumed the AUX ALT field was open until needed. The standby regulator document does explain this though, leave it closed in normal ops.

I'm curious as to the need for a breaker for the alternator field if it's already on a switch? Are those still necessary?


Yes, The B&C line of alternator controllers utilize
'crowbar' ov protection. This philosophy calls for
triggering a silicon controlled rectifier or triac
connected directly from the field supply line to ground
effectively applying a dead-short to the field power
feeder. The breaker is expected to do it's designed
duty and protect that feeder while effectively bringing
a runaway alternator to heal.

This technique was first proposed to TC aviation about
1980 when I proto-typed a controller for Beech compatible
with a particularly wicked engine/alternator combination
proposed for the "Turbine Bonanza" design being
tested at Beech. The controller meet the Beech
requirements and the technique would have flown
first its first TC mission on that airplane.

The program was scrapped but the technique was
being proofed on hundreds of OBAM aircraft in
B&C products and later picked up by Plane Power,
Lamar and others. So the short answer is yes,
you DO want to use a breaker accessible to
crew even if all other protection is remote
fuses . . . it's the one breaker you might wish
to reset ONE time to confirm that a trip was
not a nuisance event.


Bob . . .


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BMC_Dave



Joined: 04 Jul 2018
Posts: 22

PostPosted: Wed Sep 26, 2018 11:59 am    Post subject: Re: What to monitor in a dual alternator airplane Reply with quote

nuckolls.bob(at)aeroelect wrote:
Quote:
Glad I just happened across this then as it's not immediately apparent. Basing my design off Z-12 I had assumed the AUX ALT field was open until needed. The standby regulator document does explain this though, leave it closed in normal ops.

I'm curious as to the need for a breaker for the alternator field if it's already on a switch? Are those still necessary?


Yes, The B&C line of alternator controllers utilize
'crowbar' ov protection. This philosophy calls for
triggering a silicon controlled rectifier or triac
connected directly from the field supply line to ground
effectively applying a dead-short to the field power
feeder. The breaker is expected to do it's designed
duty and protect that feeder while effectively bringing
a runaway alternator to heal.

This technique was first proposed to TC aviation about
1980 when I proto-typed a controller for Beech compatible
with a particularly wicked engine/alternator combination
proposed for the "Turbine Bonanza" design being
tested at Beech. The controller meet the Beech
requirements and the technique would have flown
first its first TC mission on that airplane.

The program was scrapped but the technique was
being proofed on hundreds of OBAM aircraft in
B&C products and later picked up by Plane Power,
Lamar and others. So the short answer is yes,
you DO want to use a breaker accessible to
crew even if all other protection is remote
fuses . . . it's the one breaker you might wish
to reset ONE time to confirm that a trip was
not a nuisance event.


Bob . . .


Right on, appreciate the explanation!


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