blaat! wrote:
Does anyone understand exactly the difference between the stator ground lug being soldered to ground or not?
OK, here goes:
With permanent magnet, single phase alternators there are 2 methods to achieve FULL WAVE rectification.
That is, make an alternating current (AC) waveform into a type of direct current (DC) that fully converts all the AC to DC.
The type of DC is not a steady voltage shown by a straight line. Rather it is a pulsating waveform, with all of it on one side of the zero line.
With AC, the waves go positive half the time, negative the other half, and is useless for charging batteries or capacitors.
The battery, regulator and loads can handle the pulsating DC alright.
Method 1.
Called CENTRE TAPPED FULL WAVE SINGLE PHASE.
It uses 2 rectifying diodes.
In your Ducati, the charging coils are arranged in 2 groups. Each group is rectified by a diode connected to one of the two wires coming out of the stator, from each coil group. The other side of the diodes are connected to a load (for example a battery or lights). The other side of the load is connected to earth.
There is a connection at the other ends of the coil groups (of which there are 2 as mentioned). That connection goes to earth, so there are two wires connected to earth there. It's done that way for convenience, not having to run another wire back to the load.
Only one leg (half the number of charging coils) is active at any time the rotor is spinning.
The resulting waveform at the load is FULL WAVE DC.
Method 2.
Called BRIDGE RECTIFIED FULL WAVE SINGLE PHASE.
Uses 4 rectifying diodes.
There is no centre tap or earth connection at the stator.
All the charging coils are connected as one group.
4 diodes are needed in a so-called bridge configuration. The bridge network has 4 terminals, two of which are connected to either end of the stator coil group. The other two go to the load and earth.
All coils are actively contributing to the charge at any time the rotor is spinning.
Again, the resulting waveform at the load is FULL WAVE DC.
Being a similar physical design, that one group can have effectively twice the number of coils in series, compared to one leg of the centre-tapped system, so the output is twice as much even though the alternator is basically the same.
The conversion from a 6V to 12V stator is achieved by disconnecting from the stator earth point the 2 wires from each leg of coil groups in the centre tapped system, keeping the wires connected to each other (well insulated from anything else).
Complete the conversion by deleting the original two diodes and fitting a bridge rectifier, well attached somewhere for cooling.
Also use a regulator, which might include the bridge rectifier.
But if you want to go batteryless, the suggestion is to use a proven effective 12V regulator for the purpose, such as a Lucas ZD715.
I don't know of any proven 6V regulator suitable for batteryless usage.
