Regulator/Rectifier

[frankfast]

"Btw, the 12Volt conversion of w/c alternators is based on omitting/disconnecting the red wire/center tap and feeding a bridge rectifier from the two yellow wires. The result is a doubled AC input voltage, and in turn a 12V DC system. OK, a new R-R for 12V is needed."

So, if I used the bridge rectifier and somehow also used the Sabrisa R/R illustrated in the first post would I be able to make a 12 volt conversion? Not sure about the connections needed to do this if possible?

Also, is it possible to run the ignition and lights AC by rotating the stator in a three wire W/C alternator?

[ducwiz]

The Saprisa in fact can be used for a 12Volt conversion of a w/c single by adding two power diodes, which then form a bridge rectifier with the two internal diodes (which are in fact controllable rectifiers, better known as SCRs or thyristors). An original Ducati R-R converted by myself looks like this:



Here, the 2 diodes (salvaged from a BOSCH 3phase-alternator) are pressed into the finned cooler and then fixed on an insulating PVC lid, on top of the R-R case. The necessary connections between the diodes and the R-R's "giallo" terminals are not visible, because they are routed inside the R-R case, here they are soldered to the "giallo" terminals. On the right top of the cooler you can see a 6.3mm AMP-Faston lug, which is the new +12 Volt power output to the 12V battery; this also means that the whole cooler exposes +12V to it's environment ! Therefore, I run this modified R-R with a floating fuse placed between battery+ and the new R-R+.
Unfortunately, this method is not easily adapted for the Saprisa, as this has no detachable lid, where one can fix the new components. So one has to make an external diode fixture comprising some cooling means, and connect this to the Saprisa by an external wiring. Alternatively, you can use one of the common silicon rectifier bridges like a KBPC2502 (search the web for it, they are very cheap), or a similar type. You will only use 2 of the 4 diodes inside, that is, those connected between it's AC inputs and the positive output terminal (which is the the new +12V power output). I suggest to cut off the bridge's negative terminal to reduce the risk of electrical hazard, when it is accidentally touched i.e. by a metallic and hence conductive tool ...
The red wire from the alternator is not needed anymore, you can leave it on one of the "rosso" terminals (don't use the other one!), or insulate it and bend it away. Of course, the "marrone" wire and the corresponding R-R terminal must be connected and used as before.

Hans

[frankfast]

If I consider converting to 12 volts, that's very helpful but since I just purchased a new 6 volt battery I'll stand pat for now. Thanks.

[tobydmv]

You don't tell us which 2 of three wires you recommend to twist together. So, I presume you would take the two yellow ones.

Imho that's not a good idea. The voltages of the two yellow wires are in 180° phase angle, referred to the red center wire/tap. This means: while one side has positive polarity, the other is negative. We all learned: connecting two opposite polarities results in a short circuit, and in 0 Volt measured across the red and the two now twisted yellow wire ends. Inside the stator winding, the max. possible AC current will circulate in useless manner. This can be checked i. e. by a current clamp meter or an ammeter with very low inner resistance. It would be nice if you make this experiment with yor bike at home and report the results here.
If I'm wrong, I promise to send you a bottle of good wine.

Hans

Hans, I dont drink wine. But I am motivated by learning something. I connected the two yellow wires together and fed them into an AC terminal on the rectifier. The red wire went to the other terminal on the rectifier What do I have to lose but amps? Problem is I only have a multimeter. Earlier I measured the battery at 6.2v with the bike not running. When its running it goes up to 7.3 max around 5k rpm or so. Do you want me to separate the two yellow wires and remeasure the voltage? I think my meter can measure amps if connected in series but I dont want to break the meter. If you can walk me through a test lets do it!!!

Just checked and my meter has a 10a setting so let me know..

[frankfast]

"Unfortunately, this method is not easily adapted for the Saprisa, as this has no detachable lid, where one can fix the new components. So one has to make an external diode fixture comprising some cooling means, and connect this to the Saprisa by an external wiring. Alternatively, you can use one of the common silicon rectifier bridges like a KBPC2502 (search the web for it, they are very cheap), or a similar type. You will only use 2 of the 4 diodes inside, that is, those connected between it's AC inputs and the positive output terminal (which is the the new +12V power output). I suggest to cut off the bridge's negative terminal to reduce the risk of electrical hazard, when it is accidentally touched i.e. by a metallic and hence conductive tool ...
The red wire from the alternator is not needed anymore, you can leave it on one of the "rosso" terminals (don't use the other one!), or insulate it and bend it away. Of course, the "marrone" wire and the corresponding R-R terminal must be connected and used as before."

Hans

So just to clarify. If I can use my existing bridge rectifier, each yellow wire from the alternator must be connected to the two wires from the AC terminals of the bridge rectifier and terminated at the Giallo terminals of the Saprisa unit. From which terminal is the battery connected, the plus terminal of the bridge rectifier or the plus terminal of the Saprisa unit? The marrone terminal is then connected to the coil.

[ducwiz]

frankfast,

You must connect the battery + to the + terminal of the bridge. Again: the red wire can stay on one of the Saprisa's red terminals, but nothing should be connected to the other terminal. Best is, you wrap the Faston connector on the red wire with insulating tape and fix it with a ty-wrap to the frame, far away from the Saprisa.

good luck Hans

[ducwiz]

Hans, I dont drink wine. But I am motivated by learning something. I connected the two yellow wires together and fed them into an AC terminal on the rectifier. The red wire went to the other terminal on the rectifier What do I have to lose but amps? Problem is I only have a multimeter. Earlier I measured the battery at 6.2v with the bike not running. When its running it goes up to 7.3 max around 5k rpm or so. Do you want me to separate the two yellow wires and remeasure the voltage? I think my meter can measure amps if connected in series but I dont want to break the meter. If you can walk me through a test lets do it!!!

Just checked and my meter has a 10a setting so let me know..

Can you please disconnect the wires from the bridge but keep the connection of the 2 yellow wires, then let the engine run at different revs (say idle, 3000/min, 6000/min) and measure the AC voltage between them? Hopefully, your multimeter has an AC volts position...
Then please, report the values you took. Would be very interesting an instructive.

Hans

[tobydmv]

Can you please disconnect the wires from the bridge but keep the connection of the 2 yellow wires, then let the engine run at different revs (say idle, 3000/min, 6000/min) and measure the AC voltage between them? Hopefully, your multimeter has an AC volts position...
Then please, report the values you took. Would be very interesting an instructive.

Hans

Hans, thanks for replying I was looking forward to this test. How about I start a new thread for this effort so we don't hijack the original post?

[ducwiz]

tobydmv,

I think this idea is not bad. Let's continue in a new thread, opened by you, tomorrow. Here it's now 10:51 PM.

cheers