---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Thu 01/02/25: 3 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:21 PM - Re: Re: OVP relay in B+ lead bad idea -- corrected (Finn Lassen) 2. 06:37 PM - Re: Re: OVP relay in B+ lead bad idea -- corrected (Finn Lassen) 3. 06:48 PM - Re: Re: OVP relay in B+ lead bad idea -- corrected (Finn Lassen) ________________________________ Message 1 _____________________________________ Time: 06:21:26 PM PST US Subject: Re: AeroElectric-List: Re: OVP relay in B+ lead bad idea -- corrected From: Finn Lassen I just spotted the terrible error in the the Z-24 diagram in the Adapting_IR_Alternators_to_Aircraft.pdf document I have! It shows the alternator F-terminal connected to overvoltage relay power which is pulled to ground when OVP activates. In case of a nuisance trip you now have killed the field in the alternator, and if you have a battery failed open, there is no battery to provide startup voltage to the alternator after resetting the breaker. That's what took my plane down. If F is the internal regulator startup/sense terminal it should be connected to B+. (Any Alternator Warning relay terminal -- typically connected to positive side of field winding -- can be left unused.) I would also recommend a 30,000uF or bigger capacitor from B+ to ground. That should provide sufficiently low ripple and noise power for the alternator and its internal regulator with no (failed open or disconnected) battery. Finn On 11/15/2024 12:46 PM, user9253 wrote: > > It takes a lot less voltage and current to hold a relay closed than it does to first energize it. > Just because a circuit breaker is marked "5A" doesn't necessarily mean that it will trip at exactly 5 amps. > It should be bench tested with an adjustable current power supply. It might be tripping at much less than > 5 amps. A loose connection will generate heat which can result in a breaker tripping at > less than its rated current. The alternator field circuit breaker should not be tripping. > - > Good job making a forced landing and walking away. Many pilots panic when the engine > quits and pull back on the stick to avoid going down. The wings stall with fatal results. > The ground doesn't give. Bob Hoover quote: > "If you're faced with a forced landing, fly the thing as far into the crash as possible." > > -------- > Joe Gores > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=514526#514526 > > ________________________________ Message 2 _____________________________________ Time: 06:37:21 PM PST US Subject: Re: AeroElectric-List: Re: OVP relay in B+ lead bad idea -- corrected From: Finn Lassen Attached is what I think is the correct way to overvoltage protect an automotive internally regulated alternator with a relay in the B+ lead. Finn ________________________________ Message 3 _____________________________________ Time: 06:48:11 PM PST US From: Finn Lassen Subject: Re: AeroElectric-List: Re: OVP relay in B+ lead bad idea -- corrected Fixed attachment! Attached is what I think is the correct way to overvoltage protect an automotive internally regulated alternator with a relay in the B+ lead. Finn ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message aeroelectric-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/AeroElectric-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/aeroelectric-list Browse Digests http://www.matronics.com/digest/aeroelectric-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.