A ND alternator has internal OV protection. The theory that it will fail in a special way and not control this condition is a theory with out proof.
My only suggestion in using a ND or equiv internal regulated alternator is use a CB on the B-lead. A popular Guru of electronics promotes using a fuse for the B-lead. That is fine, but you do loose the option of pulling the b-lead CB when you choose to use a fuse. The reason for using the fuse is electrical noise, by keeping the B-lead under the cowl. I think this reason is over blown. Adding an OV relay and "crow bar" adds weight, cost, complexity and potentially can cause more problems than it solves. A simple CB on the b-lead allows the pilot to manually disconnect the alternator from the electrical system if needed. If the alternator acts up, your Hi-Lo volt warning goes off, pull the CB and land on battery power. Done deal.
The problem some claim a ND or like alternator can have is a theory and allegedly can have a severe OV condition. This is also blown way way out of proportion. When you ask for the specific cases where say a ND alternator had a massive OV condition there are no facts, data or info to support it, just urban legend. Most of the OV cases I tracked down turned out to be on old alternators with external regulators used on production planes. OV was a problem with the old equipment on certified planes. That is why OV modules where developed, because the factory planes with external regulators sucked. The folks today promoting this OV module add on or external regualtors designed the old factory systems and/or sell OV modules and alternators with external regulators with "crow bars".
There are millions of ND alternators working 24/ 7 without problems in cars, trucks and industrial equipement with excellent reliability.
A modern alternator, like a ND, has an internal regulator with OV protection built in. It is controlled with a very sophisticated IC chip. The auto industry has as much to loose with OV burning out computers and electronics as any one. A study of the National Highway Safety foundation, which tracks safety problems of automobiles, including systems: engine, transmissions, brakes and electrical systems, including the charging system. Looking at the database showed that ND alternators had no reported cases of problems, recalls or consumer complaints. Now this is not true of all brands of alternators, which did have reported issues and recalls (e.g., Ford, Hitachi). The point is the chance of having an OV problem with an internal regulator is slim to none. The reason the experts say it can happen would be a very specific failure of one specific transistor out of the blue all of sudden.
Right, sure, and you have something you want to sell me. Electronics have millions of hours of tested reliability between failures. However with that said, if you have $30,000 worth of avionics and an electrically dependant engine you need an isolated back-up battery, whether you have addition OV protection on top of your ND's internal OV protection or not.
The internal regulator was designed by engineers who know what they are doing. I hear the Japanese are good with electronics.
They designed their alternator to have OV protection internally and to work without an added on external OV module, which may damage your alternator if it has a faults trip. If you feel you need an external module, than use an external regulated alternator designed for use with an OV module. Of course you will give up a light, simple, reliable and inexpensive alternator, like a ND with internal regulation and OV protection.
Cheers George
Alternators
Use a CB on the B-lead
Linear Mode
