View Full Version : Alternators
bealiba
12th Jan 2006, 10:42
I have conflicting opinions on whether alternators should be turned off in a piston a/c when shut down. Some say doesn't matter - leave them on all the time. Others say turn on after start and off after shut down.
Any more opinions - with a reason???
Turn the power supply on before starting the engine and don't turn it off before the engine (& alt) has stopped turning, this is the safest method. The idea is to avoid surges while the unit is rotating.
The alt has a built in anti discharge device (rectifier) so can be left connected to the battery during storage etc. without discharging the batt.
On all ac I have flown, the alternaters MUST be switched off after ESD. This is because the primary coils [exciter coils? - it's been a long time!] are fed from the vital busbar, therefore draining the batteries.
FJJP,
I stand corrected, if the field/exciter supply is not isolated it will indeed drain the batts.
:)