I was about 11 miles from home yesterday and my tach started showing 5000rpm when i was running less than 2500. Then the bike started running rough. I was able to limp it home, and replaced the 7 year old HD AGM battery with a battery I had on a charger. It ran fine for a 30 mile ride. Now that battery is weak. I can't find my multi-meter but I'm hoping it's the voltage regulator. But here's my real question, and by the way, my electronics knowledge is less than adequate.
My charging system is the single phase 32 amp 1992 variety. What do I have to do to change it over to a modern three phase system? Is it just a better voltage regulator or something more?

 

Can't help you with specific part numbers or anything, but three-phase power is something I'm quite familiar with. A single-phase alternator generates a single sine wave of electricity (smoothly transversing from positive to negative polarity). This is done with a single winding (essentially). A three-phase voltage source works the same, but there are three windings oriented 120° apart and it generates three separate superimposed sine waves of electricity. At a minimum you'd need a three-phase-wound stator and the corresponding voltage regulator.

 

So, glens, with a 3 phase system, can you use smaller wires for the windings and lower rated rectifiers? In comparing two systems rated for the same output, say, 20 amps just to pick a number, would the 3 phase system have smaller wires? Would there be more coils in the stator on the 3 phase system? What is the advantage of going 3 phase?

 

Smaller wire / lower-rated components: yes and yes, though in the end you'll have pretty much the same amount of wire and of course, more components. Assuming the stator windings are connected in a delta connection the resultant power output will be a factor of the square root of 3 (or ×1.73) on any combination of two of the three leads coming out, or looking backward, the leads and components can be downsized by that same factor.

Advantages: several. You'll still need pretty much the same amount of wire either way (single or multi-phase). The RMS voltage of a sine wave alternating current is the peak voltage divided by the square root of two (1.414) [for what that's worth knowing] and since the (say) bottom portion of the sine wave is inverted by the rectifier(s) so you get a series of all upward humps, with the single-phase you'll have a lower mean voltage out of the gate than you will with three such waveforms superimposed upon one another spread out over time. [that's pretty much why the current in a delta-connected set of windings is multiplied by the factor mentioned above; the zero-voltage points of the waveforms always have both other neighbors putting out something at the time]

There's more stuff, but it's all stressed less and it provides a smoother DC out of the box.

Okay, I'll admit I'm just a tad rusty on this stuff at the moment...

 

Thanks for that, glens. I'm a bit rusty on 3 phase as well, as it's been like 30 years since I looked at it.

I wonder if you took a 2 phasestator and rewound it to three phases with smaller diameter wire (more turns), if you would wind up (so to speak) with a higher current output DC system after the rectifier. I've seen pics of 3 phase stators, and they look to have more coil "pods" (I forget the correct term) on them than the 2 phase stators.

I ask this because our MegaSquirt Fuel Injected 883 is running at about 100% of the 18 amp electrical system's capacity, as in I dropped the runninglights to 5 watt instead of 8 watt bulbs, etc.,and there is no higher output system that I can find for it, so it would be a roll-your-own type of thing. Also, maybe replacing the magnets in the rotor with rare earth ones of something. Just throwing out ideas.

 

When you say "two-phase" are you referring to split single-phase (like what you have in your house?)

I remember as a kid we had at our disposal these little generators which would rub against the side of the tire. Have you considered that for your sportie? Hahaha!

I believe you'd want the same turns count per phase as you already have now. Changing the quantity of turns per phase should change the output voltage, I believe. So in a sense, there'd be more turns (probably three times the number) but that's only because there's three phases instead of one. I'd have to see a schematic of the unit, though, before I could really suggest anything concrete. It sounds by what you're saying that they use a split-phase arrangement with a center tap on the winding and a rectifier on each leg. The output voltage from leg to leg would be twice what's needed and each one would be a half-wave-rectified circuit, resulting in full-wave rectification at half the voltage. Another up-side to this is the halving of current in the winding (as well as saving a couple of diodes to make a full-wave bridge).

 

Actually, I meant single phase instead of two phase. If I recall, the current system is single phase. Going 3 phase would have to be almost a total custom job. I could go so far as to have the metal plates waterjet cut and enamle coating them. I've built my own voltage regulators before. In this particular case, I would be looking for an improvement in the total current output of the system, not in the voltage. I'd have to think about that a bit. If an off the shelf 3 phase rectifier/regulator exists, that could be used, otherwise, I'd have to make that too. I dunno. The current system ran 2K miles to Sturgis and back and I have a lot of other projects to do.

Here's the MegaSquirt computer I built from scratch to run the EFI:

 

That's a sweet little unit! Been a while since I've done something like that myself. Stronger magnets should yield greater output. The alternator appears to be 3-phase (looking in the service manual) on the '07 tourers. Maybe it is on the sportsters as well. If nothing else, if it is, the voltage regulator is ready to go for you.

I don't know what the specific name is for the "pods" but they're poles (if that's not the correct term you were referring to anyway).