BARRY CHECK 6
Joined: 15 Mar 2011
Posts: 738
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 Posted: Mon Aug 19, 2013 1:29 am Post subject: AeroElectric-List: Re: Rotax 912 UL alternator drop-out |
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Good report Paul.
A practical approach has prevailed.
Now since you know 10 Amps will overload the system and 5 to 6 Amps is borderline for an overload. �The next thing to do is COOL the unit and apply 5 to 6 Amps and see if it stays online. �If it stays online you now know cooling is required.
Barry
On Sun, Aug 18, 2013 at 11:57 AM, Paul Kuntz <paul.r.kuntz(at)gmail.com (paul.r.kuntz(at)gmail.com)> wrote:
[quote]Several inputs suggested checking the connections on the leads coming from the alternator, and checking the system ground connections.� I checked the faston-type alternator lead connections, which were clean and tight.� I checked all of the ground connections, which were also tight.� Yesterday I went up for a test flight and confirmed the symptoms under varying system loads.� The normal system voltage with alternator on line is 13.8 volts, which is consistent with what others are reporting for the Rotax Ducati regulator.� I see a max load of 10 amps with everything running, so I am satisfied that the total load is well within the standard Rotax system capacity.� I also observed that the system voltage drops to 13.5 volts at the 10 amp max load, which seems abnormal.� Under this max load, the alternator dropped out after a few minutes, indicated by system voltage dropping to around 12.5 volts -- consistent with fully charged lead-acid battery.
When I reduced the load to 3 amps, which is my practical minimum (one Dynon display, radio and transponder), the alternator came back and stayed there, with system voltage at the normal regulator set point of 13.8 volts.�
I repeated this experiment a few times for various loads, finding that a total load above 5 or 6 amps will cause the alternator to drop out after a few minutes, and that it will come back when the load is reduced to 3 amps.�
I am pretty well convinced that my voltage regulator is bad.� I did learn from comments on this issue that Van's includes a voltage regulator cooling kit with its lighting kit for the RV-12, consisting of a length of plastic tubing that connects from the air intake duct to a shroud over the regulator, providing a direct blast of cooling air to counteract the increased electrical load of the lighting.� So there is certainly indication that the Ducati regulator is susceptible to overheating under load.� The RV-12 regulator is on the engine side of the firewall, however, and mine is on the cabin side.� At 10 amps with the regulator mounted in the cockpit environment, I'm thinking the regulator should be able to handle the load without supplemental cooling.� Others have noted the not-so-good reputation of the Ducati regulator, but there are thousands of them in service on Rotax engines worldwide, so rather than tackle a reconfiguration of my regulator and wiring installation at this point , I ordered a replacement Ducati from Lockwood Aviation and will see how it goes. I also ordered a overvoltage protection module from B&C, since the Pipistrel electrical system does not include one.� I'll install it with the new voltage regulator.
I'll report my findings after installing the new regulator.�
Paul Kuntz
On Sat, Aug 10, 2013 at 10:21 PM, Paul Kuntz <paul.r.kuntz(at)gmail.com (paul.r.kuntz(at)gmail.com)> wrote:
| Quote: | Thanks for the tips, everyone. �I concur with Bob that my Ducati regulator is done for and should be replaced. �I will take a look at the Schicke�unit�that Peter mentioned.
Cheers,
Paul Kuntz
On Friday, August 9, 2013, Robert L. Nuckolls, III wrote:
| Quote: | --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com>
At 12:55 PM 8/9/2013, you wrote:
| Quote: | Thanks for the tip. �I'll check this cooling shroud idea. �I'm also wondering if my regulator has already been compromised. �Any opinions on what my repeated fail/recover situation indicates? �I would guess that it cycled between failed and recovered 8 or 10 times before we established a state where it stayed on line, limited to a total current draw of 3 amps.
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� If your regulator can't carry 10A without cooling, it's
� probably broke. A functional part should be capable of
� rated output for the alternator which is on the order
� of 18A. I've not heard of any mass-movements to forced
� air cool these regulators.
� Bob . . .
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