Nigel, Fascinating and impressively erudite. You have
totally convinced me that the way all new builders should
go is with a Mofset bit of kit. However my personal
solution is to take the odd Ducatti at sale price off
anyone not planning to fit them and fly with a spare! In
1000hrs I have had one failure. That was inconveniently
1/3 way between Holland and Clacton, but there was enough
juice in the battery to get me all the way home with a bit
of thoughtful systems management. I currently fly with
Rowland's spurned new Ducatti in my spares department
under pax seat, but am prepared to offer a modest price
for another unwanted Ducatti!
Regards, David
"nigel_graham@m-tecque.co.uk"
<nigel_graham@m-tecque.co.uk> wrote:
>
> I have followed this discussion with great interest and
>with an increasing sense of Dj vu.
> When the issue of regulator/rectifier failures occur
>withing the Rotax community, the standard fix seems to be
>to simply replace like with like (at elevated Rotax
>pricing) and fly on until the next unit fails.
>
> Up until about five years ago, nearly all modern
>Japanese motorcycles used the same technology as that
>found on the Rotax 91x series engines, permanent-magnet
>generators controlled by SCR rectifier/regulators. It may
>come as some surprise that for an industry renowned for
>precision and reliability, nearly all of these major
>motorcycle manufactures have at some time, been plagued
>by problems with their SCR based rectifier/regulators
>failing and burning out alternators and wiring, cooking
>batteries and in extreme cases, squirting unregulated AC
>into the wiring loom and blowing up ECUs. It was just
>such a failure that "sparked" my interest :-(
>
> Known as "Shunt Regulators" the SCR technology runs
>extremely hot and requires more cooling air than modern
>styling and space allows.
> The solution was a move towards MOSFET controlled
>regulators and the numerous web-based one-make discussion
>groups were full of information and advice on the reasons
>for failure, the benefits of the change and practical
>advice on how to convert.
>
> It was by trawling these groups that I was able to build
>up a good understanding of how these R/Rs worked, what
>was causing the problem and what the potential solution
>might be. I compiled what I considered to be the best
>informed snippets of information into the attached
>document.
> The first half gives an overview of a typical design of
>an SCR Rectifier/Regulator for use on a permanent-magnet
>generating system and the second half discussed the
>relative merrits of SCR versus MOSFET.
>
> It would be interesting to know which technology the the
>after-market Schicker and Silent-Hektic R/Rs use.
>
> Nigel
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