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vmenkal(at)mac.com
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 Posted: Sat Nov 12, 2011 2:35 pm Post subject: Electrical Help |
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Some "electrifying" questions that I would greatly appreciate being "enlightened" on.
It appears that the rotax 912 ULS charging system is an alternator (i.e. there are no permanent magnets, there is a "field" circuit on the rectifier and the field coils need a bit of battery power for the system to operate) but the manuals refer to the built in power system as a "generator". Is this just a translation item?
If indeed I have an alternator, why do we not bother with the alternator field disconnect (wiring diagrams just show direct connection to the downstream side of the master solenoid?
A more general question, all the circuit diagrams I have for the engine, my composite design panel and general use circuit diagrams do not show a fuse or breaker on the primary power supply to the main bus (power panel) from the At up to 50A, Im thinking that this circuit should be protected against short circuit - wouldn't a short cause a fire hazard?
If a fuse or circuit breaker is a good idea, Im assuming that I would install as close as possible to the master solenoid - any advice re circuit breaker or fuse and location?
Appreciate any words of wisdom.
Thanx Vic
Victor Menkal,P.Eng.
Whitehorse, Yukon, Canada
CH750 912ULS-2
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Martymason
Joined: 17 Apr 2009
Posts: 20
Location: Norcross, GA
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| Posted: Sun Nov 13, 2011 8:50 am Post subject: Electrical Help |
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You Wrote:
Time: 02:35:04 PM PST US
From: Victor Menkal <vmenkal(at)mac.com (vmenkal(at)mac.com)>
Subject: Electrical Help
Some "electrifying" questions that I would greatly appreciate being "enlightened"
on.
It appears that the rotax 912 ULS charging system is an alternator (i.e. there
are no permanent magnets, there is a "field" circuit on the rectifier and the
field coils need a bit of battery power for the system to operate) but the manuals
refer to the built in power system as a "generator". Is this just a translation
item?
If indeed I have an alternator, why do we not bother with the alternator field
disconnect (wiring diagrams just show direct connection to the downstream side
of the master solenoid?
A more general question, all the circuit diagrams I have for the engine, my composite
design panel and general use circuit diagrams do not show a fuse or breaker
on the primary power supply to the main bus (power panel) from the
At up to 50A, Im thinking that this circuit should be protected against short
circuit - wouldn't a short cause a fire hazard?
If a fuse or circuit breaker is a good idea, Im assuming that I would install as
close as possible to the master solenoid - any advice re circuit breaker or
fuse and location?
Appreciate any words of wisdom.
Thanx Vic
Victor Menkal,P.Eng.
Whitehorse, Yukon, Canada
CH750 912ULS-2
The Rotax generator is a permanent magnet alternator where the magnets are in the flywheel. Therefore there is no field connection. The regulator controls the output voltage by either switching the output or by dumping the excess energy as heat. The regulator must be cooled to prevent its destruction.
The 912 - 914 alternator with the Ducatti regulator is only capable of 20 amps max. Crowbar protection for the regulator output would use a 20 amp circuit breaker so no other protection is called for.
The aeroelectric connection list is a better forum for electrical questions.
Marty Mason
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Marty Mason
Norcross, GA |
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s.clive.richards(at)homec
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| Posted: Sun Nov 13, 2011 9:57 am Post subject: Electrical Help |
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Victor
I have had a look at the rotax manual as I will have to wire a plane in future. You may be confusing the built in Permanent Magnet Generator item 4 in manual ie G wires to regulator with an optional External Alternator item 10 to 12 this is shown protected by a 50 A fuse or circuit breaker, the PMG regulator is shown protected by a 25 A fuse or circuit breaker the earlier manual said a 30 A slow blow fuse. I am surprised their is no fuse shown in a G wire.
See manual notes re essential capacitor to protect regulator & no switching between B+ & C terminal of regulator.
I believe the regulator needs battery power to start output but is then self sustaining so you will need a relay to Isolate with master switch but leave capacitor connected.
I would ask on aerolectric list.
Clive do not archive
[quote] ---
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