I've heard 90, 100 or more volts.

If you don't believe it and you have an alternator with an external voltage regulator, you could try feeding the field winding the full 12 volts, with the alternator running at full speed. Of course you might fry the diodes in the alternator in the process.

Finn

DaveLeonard wrote:

Al, you are right about now having the lack of over-voltage protection.  All I have in line is a fusable link rignt now.  Fortunately, all of my expensive avionics can tolerate voltages of at least 28V without being affected. 

 

If a voltage regulator fails, how high can the voltage go?

 

Dave Leonard

Dave;

 

That’s interesting.  Makes me wonder whether I should put a scope on voltage and see if it is smooth. 

 

The downside of connecting the field to the output, as I’m sure you know, is that you now have the risk of a runaway voltage condition if the VR fails.  I guess the odds are low, but the costs could be high. Avionics?

 

I assume that you have a breaker (or fuse) in the alt field circuit.  You can put a “crowbar” circuit between the field lead and ground that will trip the breaker in an over-voltage condition.  I got one from Aeroelectric.

 

Al