This gizmo 'ere:
As for yer basic BMW 280W 3-phase alternator with self-excitation rotor, (big-block Tontis and R-series BMW twins).
Been trying to get my head around how the orange wire works, in fact how any of it works really so yesterday afternoon I put it on a power supply to find out. At this stage this power supply merely represented a battery, and as it happened that’s all I needed to do…
The instructions say “The RR45 must ‘sense’ a threshold current of 120mA down the ORANGE wire before it will wake up from rest and go” ~ yes true ~ sort of.
I didn’t measure 120mA but instead 63mA, and as far as I can tell it is a constant current source.
So, where the instructions then say you can use the dash panel warning lamp bulb with the orange wire, and that a 1.2W bulb is not ‘big’ enough, it turns out it will, in this case (63mA), light up, if dimly. Where it then says a 3W bulb is ‘too much’ and won’t light up, so a 2W bulb is recommended, that too will be ‘too much’ and not light up! (In this example I’ve got here.)
In all cases though the regulator is definitely turned on, even by a 1.2W bulb.
What happens then is, DC current goes out the rotor output wire (brown) straightaway, i.e. it’s getting it directly from the ‘battery’. (No AC input at all on the yellow stator wires for this demonstration.)
So, it seems what we have here is, if you like, 2 ‘separate’ parts ~
#1. a 6-diode rectifier block, for 3-phase AC to battery (only).
#2. a regulator that runs directly off the battery Voltage.
If so then the internal block diagram shown here (inset) is not very accurate (because it implies rotor current comes from the stator via 3 extra diodes only when it’s running):
It’s worth knowing though that as soon as the ignition is turned on there’ll be 4 Amps going to the rotor immediately from the battery, add to that say another 4 Amps (typically) for the ignition system you’ve got 8 Amps on the go already before you press the starter. I was going to connect the orange wire via the kill switch anyway, and I’m now more convinced this is a good idea.
Still not sure how the orange wire constant current source / start-up switch works, without going into some complex circuitry (entirely imagined), as there isn’t a lot of room at all in the resin block in which it all lives, so I’m not sure how sophisticated it really is. On the other hand, surface mount devices are a distinct possibility, allowing maximum miniaturisation. Could even be an integrated circuit in there.
I’m guessing the rotor output will turn off if the ‘battery’ Voltage is raised by an appropriate amount, but haven’t tried it yet.
Some sophisticated regulator circuits involve an oscillator to switch the rotor with a variable mark-space ratio, but the simplest method is merely to monitor the output Voltage and switch according to that.
Still scratching my head how to make the dashboard bulb work efficiently…