---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Fri 12/05/25: 2 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 09:53 AM - Re: resistance in solenoid (Eric Page) 2. 11:42 AM - Re: resistance in solenoid (user9253) ________________________________ Message 1 _____________________________________ Time: 09:53:34 AM PST US Subject: AeroElectric-List: Re: resistance in solenoid From: "Eric Page" alfuller194(at)gmail.com wrote: > In the original post, the device in question was described as a 'continuous' solenoid. > > Is that relevant, or am I just being pedantic? The primary difference between continuous and intermittent duty solenoids is in their coils. Continuous duty generally have higher resistance coils designed to draw less current and therefore heat up less. They're designed to be on all the time without overheating. Intermittent duty solenoids have lower resistance coils that draw larger current. This makes them close "harder" at the expense of greater heat, so they can't stay on continuously. There is often a difference in their contacts as well. Intermittent duty solenoids are often rated for much higher surge current than continuous duty. Their aggressive closing velocity and pressure helps them carry higher loads. The ones we use as battery contactors are continuous duty, while our starter contactors are intermittent duty. Whether or not to run starter currents through an already-closed battery contactor is open to debate, but I'm not doing it. There are ways to protect the starter circuit against unwanted activation without doing so (one example: a small automotive relay interrupting the starter switch circuit, with its coil in parallel with the battery contactor's coil, so that it pulls in at the same time as the battery contactor). Does the OP's aircraft route starter current through the battery solenoid? If so, could that have burned its contacts, causing a high resistance connection? Read this topic online here: http://forums.matronics.com/viewtopic.php?p=516720#516720 ________________________________ Message 2 _____________________________________ Time: 11:42:15 AM PST US Subject: AeroElectric-List: Re: resistance in solenoid From: "user9253" The OP sent me a private email. He indicated that there are two continuous duty contactors, only one used at a time. Which ever one is energized will carry starter current and aircraft load. He said the engine cranks just fine. I assume there is a separate starter contactor. I do not have a schematic. He measured the voltage drop across each continuous duty contactor when it was independently energized. He measured 0.82v across one contactor and 0.42v across the other contactor with the voltmeter probes on each large stud and with the contactor energized. I suggested that he turn each contactor on and off 100 times in an attempt to wear away any contact oxidation, then repeat the voltage measurements. -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=516721#516721 ------------------------------------------------------------------------------------- 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.