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Over-Voltage Protection

mbell

Well Known Member
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?
 
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.
 
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.
 
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.
 
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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