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Some may recall I threatened to report on what happenes if you
change the>way the standard 3 lead alternator is
wired......>>First off I took some measurements of alternator
output using different>regulators and methods of connection,
then I changed the way the 2 sets of>alternator coils are wired
and measured the output again>
>Conclusion is that the rewired configuration does produce
more power ->putting it another way, it balances the load at
lower RPM.>>Measurement of output is a little bit of a
challenge, as it's the max>capability at any rpm that needs to
be measured - and the regulator may be>doing it's job and
reducing the output depending on the battery state. So>I
recorded the rpm at which various loads were balanced.>>I put
a 0.022 ohm resistor between the battery + terminal and the
wiring>harness, and put a digital voltmeter across that, so 0
volts => alternator>output was balancing the load. Biggest
inaccuracy was measuring rpm with a>(new) smiths tacho.
>>I took measurements of rpm needed for load balance with
just the RITA>ignition (with 3 ohm twin output Dyna coil),
ignition plus>side/pilot/instrument(side) lights, ignition plus
side lights and 55W dip,>and finally ignition plus side lights
and 100W main.>>First configuration was the stock set-up and
3 lead regulator>>load rpm for
balance>-------------------------------------->RITA
2,250>RITA + side 2,400>RITA + side + 55W 3,250
>RITA + side+ 100W 3,800>>Next I replaced the regulator
with 2 diodes to see if the regulator was>losing any power - red
wire left connected to + and white wires connected>via diodes to
ground. Results were identical, so the stock regulator
works>just fine.>>Next configuration was to disconnect the
red wire (centre tap) and to>connect the white wires to the AC
terminals of a bridge rectifier. As>expected, the output is much
higher at low rpm, but it never balances the>higher load>
>load rpm for
balance>-------------------------------------->RITA
1,400>RITA + side 1,700>RITA + side + 55W 4,000>RITA +
side+ 100W N/A>>Finally I reconnected the alternator leads at
the alternator, and i guess>this needs a bit more
explanation>>Here's the stock arrangement:>>
____white
>/>\>/
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>\____red___ to +ve>/>\>/>\____white>>The
outputs of the white leads are out of phase - when one goes
positive,
>the other goes negative. Stock regulator therefore uses the
output of only>one of the white wires at any point in time: they
take it in turns to>contribute current. (and just to confuse,
the regulator does this by>connecting them to ground)>>If
you take the stator out of the cover, you'll see three terminals
to>which the solid copper wire of the coils and the output wires
are soldered.> I unsoldered the centre terminal and took one of
the solid copper wires>off and connected it to the end terminal
- move the one that measures open>circuit to the terminal you're
going to solder it to. I reconnected the>red wire to the end one
with both sets of coils attached, and the loose>white one to the
middle
>>Before:>
____--------white>/>\>/>\____>
____--------red>/>\>/>\____--------white>
>>After:> ____--------white>/>\>/>\>
____-------white> /> \> />
\____>________-------red>>This arrangement has both coils
contributing IN phase: thay both go>positive at the same time.
If both coils had the same number of turns you>could connect
both white wires together and use a 2 lead regulator -
I'll>check some time. Not being sure, I kept the wires separate
and used a 3>phase 400V 35A bridge rectifier (they have 3 AC
terminals and contain 3>pairs of diodes) I put a Lucas zener
diode in as a regulator. Rectifier>and zener (on a heatsink) are
mounted on an ally plate where the rear air>filter used to
be.>>load rpm for
balance>--------------------------------------
>RITA 2,100>RITA + side 2,300>RITA + side + 55W
3,100
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>RITA + side + 100W 3,400>>So, it'll run a 100W
headlight at 400rpm less. May not sound much, but it's>quite a
lot in the context of the rev range used in town or traffic.
I'm>confident I'll now be able to use an 80/100 headlight and am
leaving the>alternator like this>
>I measured the charge rate at 4000 rpm with main beam at
about 1.5A and>when I get time I'll take some output current
measurements and compare with>the data in the workshop manual
for the stock system.>>Regards,>James
