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gilles.thesee(at)free.fr
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 Posted: Mon Jan 09, 2017 10:31 am Post subject: Rotax 912iS : alternator relay ? |
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Hi all,
Here is another Rotax 912iS funny question.
In its Operator's Manual, Rotax states that it has "an overvoltage
protection [...] integrated in the FUSEBOX".
Nevertheless some owners on the Rotax Owners Forum report having
experienced overvoltage events, which would mean that the regulator & OV
protection are not very reliable.
According to the Rotax wiring diagram, the main bus is connected to the
"fusebox" with no means of of disconnection (see attached picture of
Rotax wiring redrawn)
If for some reason the pilot wishes to remove power from the ship, he'll
open the master switch but the alternator may still deliver power to the
bus.
Wouldn't it be advisable to add an alternator relay and an OV protection ?
Thank you,
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr
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user9253
Joined: 28 Mar 2008
Posts: 1938
Location: Riley TWP Michigan
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| Posted: Mon Jan 09, 2017 8:19 pm Post subject: Re: Rotax 912iS : alternator relay ? |
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Gilles,
I modified your schematic and added information gleaned from Rotax-Owner.com.
As for over-voltage protection, an alternator switch could be inserted in the wire going to X3.3 It might take you a minute or two to recognize the over-voltage condition and shut off the switch. But most modern avionics are rated up to 30 volts. And the battery will resist the increased voltage for a while. Hundreds of RV-12s are flying without over-voltage protection. I am not necessarily recommending not installing over-voltage protection, but it is an option.
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_________________
Joe Gores |
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gilles.thesee(at)free.fr
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| Posted: Tue Jan 10, 2017 2:54 am Post subject: Rotax 912iS : alternator relay ? |
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Le 10/01/2017 à 05:19, user9253 a écrit :
| Quote: |
Gilles,
I modified your schematic and added information gleaned from Rotax-Owner.com.
As for over-voltage protection, an alternator switch could be inserted in the wire going to X3.3 It might take you a minute or two to recognize the over-voltage condition and shut off the switch. But most modern avionics are rated up to 30 volts. And the battery will resist the increased voltage for a while. Hundreds of RV-12s are flying without over-voltage protection. I am not necessarily recommending not installing over-voltage protection, but it is an option.
Joe,
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Thank you for having taken the time to examine and comment the schematic.
You are right, most avionics can withstand up to 30 V, but unfortunately
not all of the appliances in the project, and my partners are asking for
some protection.
Initially I thought that the built-in Rotax OV protection would be
enough, but as some owners had over-voltage events, obviously the
voltage regulators can fail (there has already been a regulator update
by Rotax), and the OV protection did not catch or contain the event.
So I'm wondering...
Thank you for your help,
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr
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