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  #1  
Old 08-22-2018, 12:15 PM
mbell mbell is offline
 
Join Date: Aug 2005
Posts: 108
Default Over-Voltage Protection

Does the RV-12 have any built-in over-voltage protection? I know of at least one SLSA make without it, so it must not be a certification requirement. If so, is the Rotax charging system not prone to a high-voltage failure?
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  #2  
Old 08-22-2018, 12:53 PM
pilotyoung pilotyoung is offline
 
Join Date: Jan 2018
Location: Birmingham, AL
Posts: 40
Default Over Voltage Protection

I am not an EE but my understanding is there is not any over voltage protection in the RV-12.

I just ordered a Silent Hektik voltage regulator at a cost of $300.00 delivered and the main reason I did it is because the Silent Hektik has built-in over voltage protection.

I decided I have thousands of dollars of avionics and it is worth $300.00 to protect them.

Dynon says it's avionics have robust electrical protection built-in but I figured it was worth an additional $300.00 as insurance.
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  #3  
Old 08-22-2018, 06:04 PM
Mich48041 Mich48041 is offline
 
Join Date: Apr 2008
Location: Riley TWP MI
Posts: 2,678
Default

RV-12s with the Rotax ULS do not have over-voltage protection. Luckily it seems that the Ducati Regulator fails with low voltage, not high, at least so far.
Over-voltage protection is mandatory for aircraft with the EarthX battery. Both EarthX and modern avionics have built-in over-voltage protection. But they have their limits. A runaway alternator can exceed those limits.
If your plane does not have over-voltage protection and an over-voltage condition does occur, would you rather have a switch to immediately disconnect the charging system, or would you be content locating and pulling the alternator fuse? I ask because the latter method has been proposed. or so I have been told.
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  #4  
Old 08-22-2018, 11:21 PM
RFSchaller RFSchaller is offline
 
Join Date: Oct 2010
Location: Phoenix, AZ
Posts: 2,296
Default

You always have manual protection: pull the fuse!😜
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  #5  
Old 08-23-2018, 02:29 PM
mbell mbell is offline
 
Join Date: Aug 2005
Posts: 108
Default

Bob Nuckolls' AeroElectric Connection shows a schematic for the Rotax that includes OVP, and B&C sells the parts. Seems easy enough to do, but obviously not a common thing to do. I didn't realize the Silent Hektik VR has it built-in, at least in one model.
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RV4-->6-->6A.
AirCam under construction.
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  #6  
Old 08-23-2018, 08:31 PM
pilotyoung pilotyoung is offline
 
Join Date: Jan 2018
Location: Birmingham, AL
Posts: 40
Default Over voltage protection

could you provide a link to that drawing?

Thanks.
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  #7  
Old 08-23-2018, 08:49 PM
Mich48041 Mich48041 is offline
 
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Location: Riley TWP MI
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LINK to Bob Nuckolls' drawing.
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  #8  
Old 08-23-2018, 09:41 PM
pilotyoung pilotyoung is offline
 
Join Date: Jan 2018
Location: Birmingham, AL
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Default Over Voltage Protection

Thanks for the link.
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  #9  
Old 08-24-2018, 06:09 AM
BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
Posts: 4,412
Default Of note . . .

One should determine what type alternator is being used.

OVPM for a PM (permanent magnet) alternator and a claw pole alternator will not be exactly the same. These are very different electrical machines. Bob's OVPM circuit is a crowbar for the field on a claw pole alternator design to blow the 5 amp fuse.

The crowbar circuit can be (should be) scaled up to blow the main fuse for the PM alternator if desired. It is not uncommon to do this on highly rated and expensive equipment, always to limit any catastrophic damage. Frequently exercised to protect against software glitches in development of brushless DC motor drive inverter systems. It's what fuses are for, to blow, even it it is large.

Edit: I should have looked at the drawing - using the same OVPM to blow the alternator disconnect supply will work for the PM alternator as well.
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Last edited by BillL : 08-24-2018 at 06:13 AM.
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