---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Sun 09/04/16: 1 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 11:15 AM - Re: Ducati Regulator (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 11:15:00 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Ducati Regulator At 01:27 PM 9/1/2016, you wrote: >For those interested in learning more about the >Ducati regulator used in Rotax installations, >the following post appeared on >rotax-owner.com forum. >Note that there is an embedded link that goes to some technical information. > > >The 22A "Max" is a=C2 continuous=C2 current rating. > >Ducati uses a power MOSFET as a switching >regulator for the DC output. See the=C2 >BUZ60 >datasheet=C2 ... But if you peruse the graphs >there, it appears that the device's 22A 'pulsed >current' rating is dependent on pulse width >(duty cycle), and more than anything the ability >of the device to dissipate heat. The device >itself can only (safely) supply its maximum >rated output if its own case temperature is kept >to 47C or below. Assuming the module package is >100% efficient at drawing the heat away from the >MOSFET, you can extrapolate from the MOSFET >performance curves that it shouldn't put out >more than about 17.6 amperes at the "maximum" >allowable module temperature of 80C.So I think >your estimate of 16A continuous is a very good 'conservative real-world number' I checked the article cited. Unfortunately, a few items of fact cited are poorly interpreted. The BUZ60 device is inappropriate to this task. It's a HIGH voltage, LOW current device with very HIGH on resistance. There are hundreds of devices more suited to this kind of service. The Ducatti regulator is demonstrably under-cooled. The samples seen in a disassembled condition appear to depend on POTTING COMPOUND to conduct heat energy from the switching devices to the outside world via what radiating fins do exist on the housing. This is a mystifying concept that was tried by this writer only once . . . a long time ago and never since. My friendly CNC driver has carved out some parts that fit into this proof of concept package http://tinyurl.com/zcxn6lr I'm exploring options for a PM r/r wherein the ability to control generations and rejection of heat are know quantities and tailored to design goals. Thermal resistance between the silicon junctions and outside world will be minimized . . there will be no potting compound. It is a mystery as to why the Rotax/Ducatti marriage has persisted for so long . . . but the answer is immaterial. It time to figure out how to do better. Bob . . . ------------------------------------------------------------------------------------- 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.