Nigel Harrison wrote:
>
>
> Dear all,
> It would appear that I'm unusual in planning to install a 24V system in my
> Europa. Skydrive have advised re the alternator saying "The internal
> alternator gives an AC voltage above 24 V at a speed of about 3000 rpm,
> which may possibly be suitable, but you would have to design or procure a
> rectifier/regulator for 24 V."
> Does anyone have any information on a suitable rectifier/regulator?
> Thanks
> Nigel Harrison
I guess my question, and maybe others is : WHY ?
I am certainly not sure that the output which maxes at 19A
at 12v would be as much as 19A at 24V.
Better to stick to the design as already proven. Have two
batteries, with charging and changeover if you wish. A
17Ah 24V battery will be about the same weight as two 17Ah
12V batteries [and has the same energy capacity].
In normal use - have only one battery on line, but
alternate (I mean swop from one to the other) to keep them
both charged. Then if you have a problem with the
alternator, you can run the on-line battery down to almost
zero, and then you can change over and do the same with
the other.
Having two 17Ah batteries might be better than one 34Ah
battery, but two 12 Ah would be sufficient.
If you have 912 or 914 then 12V is sufficient for
starting. If you have 912S, or plan to order one, make
sure you have the Heavy Duty Starter.
I am not sure about 24V through the 12V starter but it
might be OK as it is very short duration usage. (The
RS1600 rally car had a 12V starter but as it was a pig to
start when hot it had two batteries and used 24 volts for
starting. there was a clever system of relays to change
the batteries from parallel (for normal use and charging)
to series (for starting). It worked well except when one
of the relays got a bit tardy - at which point there
tended to be a dead short !
Also keep in mind that the quoted figure of 24V above 3000
rpm may be a peak voltage which would be somewhat reduced
after rectification. To charge a 24V battery you need 28V
or more after rectification to DC.
The avionics will run at 24V, but what about the fuel
pump, trim motor and the flap motor ? Also the engine rpm,
temp and pressure gauges ?
After all if you have a charging problem you don't want to
be up there any longer than necessary. And if the problem
is in the alternator windings don't fogetthat there are 10
sets. 8 are used for charging and the other 2 in the same
location are used for the magnetos.
Just my two cents worth !
Richard
Richard F.W. Holder 01279 842804 (POTS)
Bell House, Bell Lane, 01279 842942 (fax)
Widford, Ware, Herts, 07860 367423 (mobile)
SG12 8SH email : richard.holder@avnet.co.uk
Europa Classic Tri-gear : G-OWWW, High Cross
PA-28-181 : Piper Archer : G-JANA, EGSG (Stapleford)
|