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Re: RE: Figure Z-7 Update . . .

Subject: Re: RE: Figure Z-7 Update . . .
From: Robert L. Nuckolls III <nuckolls@aeroelectric.com>
Date: Sun, 7 Feb 1999 15:37:45
>Funny thing - last night I downloaded the corrected Z-7 drawing you had
>announced in your message, and tonight I find this new message from you
>announcing the latest, once more "revised" version of the same drawing. Of
>course, I just HAD to download that one too, and - lo and behold! - this
>turns out to be nothing new but rather exactly the setup you sent me some
>years ago, and which I then fitted to my Rotax 2-stroke-engined Kitfox.

   Hmmm . . . first thing to go when you get old is your memory,
   and I forget what the second thing was . . . 

   I do seem to recall having that conversation with you and
   probably with several others over the years . . . don't know
   why I missed getting that incorporated earlier. I guess
   I still hoped that people would have some form of l.v. warning
   which does the same thing . . . the system will go into
   low volts a seconds after the alternator trips off line.

>All I can say is that I can really recommend this system to anyone using one
>of these whizz engines. On my airplane, I had no less than two total
>failures of the infamous "cheapie" regulator supplied as standard by Rotax,
>plus a couple of intermittent instances of overvoltage. The "crowbar" setup
>did its trick exactly as it is supposed to do, and I must confess that in at
>least one of these occurrences I would surely not have caught the failure
>condition before some damage would have been inflicted.

   I'd REALLY like to figure out a way to do a REAL rectifier/regulator
   for that engine. The #1 problem is HEAT. With one diode and one
   SCR in conduction on each half-cycle of the AC out, there's a total
   of about 2 volts dropped.  Multiplied by 18 amps and you've got
   36 watts of heat to dump.  I think most people are having trouble
   with their designs because of inadequate heat managment.

   I'd also like to see the trigger system for the SCR get smarter.
   I don't see any reason why that regulator shouldn't be as tightly
   in command of bus voltage as it's automotive counterparts . . .
   +/- 100 mV is in order.  One of these days . . .



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