Over voltage protection

[tcone1]

Hello People,

I am sad to report that the impossible (according to some) has happened. My internally regulated alternator failed HIGH. I feel very lucky that the only things that the voltage transient killed were all the Van's engine and fuel gauges...all 10 of them. Oh, and the landing and taxi lights. Everything else survived. Total time in service was 70 hours.

I've had the alternator rebuilt...Van's is backordered...because they won't be selling them any longer.

What are people doing in terms of overvoltage protection? I would like to keep the modification to a minimum, so an inline overvoltage relay would be great, but my circuit design skills perished...all knowledge is perishable when left in my little pea sized brain for years and years. Is there a commercially available solution?

Thanks,

Tim

No animals were harmed, but yes, electrolytic capacitors were harmed during the production of this film...they blew their little wads (literally). Some of them blew with enough energy to dent the back side of the gauge faces.

[DGlaeser]

If your IR alternator doesn't turn off when you remove the activation voltage, then the only way to protect from an OV situation is to put a contactor on the B lead, and use a commercially available OV module (from B&C or Perihelion) to control that contactor. See any of Bob Nuckolls diagrams for a schematic, but basically the ALT position of your master switch powers the OVP device which closes the B lead contactor and provides the activation voltage to the IR.

That architecture has caused problems with some IR alternators (particularly Van's) when the B lead contactor is opened while the alternator is under load (by turning off the master switch before shutting down the engine). So the operational solution is to turn off the master ONLY after stopping the engine. Bob N is working on a device to resolve this problem, but it's not available yet.

[Jamie]

By far, the easiest, most elegant solution to your problem is to simply use a plane-power alternator. Internally regulated with internal OV protection. All the technical details are on their site.

http://www.plane-power.com/

Van's sells it here.

I have this unit on my RV and am very happy with it so far.

[az_gila]

Tim... were the avionics switched on? Did they survive? gil A

[tcone1]

Gil,

Yes the avionics master was on. All of the radios are fine, the efis and map are great...

[Geico266]

Plane Power is the only way to go IMHO. The voltage protection is worth it's weight in gold, literally.

You were lucky to get on the ground without a fire.

[Bill Dicus]

Do you mean that the B&C OV protection device is OK with Vans IR alternator if I simply avoid turning alt "off" before stopping the engine? That would be great for me if true - already have Vans alternator (mounted, with prop and belt) and the OV module from B&C. Thanks for any input. Bill

[alpinelakespilot2000]

Originally Posted by Bill Dicus

Do you mean that the B&C OV protection device is OK with Vans IR alternator if I simply avoid turning alt "off" before stopping the engine? That would be great for me if true - already have Vans alternator (mounted, with prop and belt) and the OV module from B&C. Thanks for any input. Bill

That's my (limited) understanding, Bill. The only problem is that more than once in the past have I accidently turned off the master in flight when my head was somewhere else. I'm concerned that a little slip like that could have disastrous consequences. It shouldn't. Others with more knowledge should speak to this though.

[az_gila]

Originally Posted by tcone1

Gil,

Yes the avionics master was on. All of the radios are fine, the efis and map are great...

That's really interesting given previous discussions on the usefulness of an Avionics Master switch...

The overvoltage was severe enough to blow light bulbs, but the avionics all survived.

There really must be some good to that DO-160 testing after all....

..and you have finalized my plan for no Avionics Master - heck - this modern radio stuff is good...

gil A

PS - I don't think Vans claims DO-160 compliance for his cheap engine gauges...

[Bill Dicus]

Steve: thanks for your reply. Hope it doesn't happen to me in the early hours. If so will probably buy Plane Power or B&C. Bill