There is oil injected into the case at 2 points, just none directed directly onto the stator. It is cooled and in my opinion, not very well by splash only.
You will usually loose one coil only in the alternator, even if the problem is caused by external heat. The odds that all 3 phases age and fail at exactly the same time is remote and this particular alternator is wound with good separation between phases. Anyways when a phase finally fails, it does so by shorting at which point it cooks and turns black pretty instantly. At this point it may short to other phases and take them all, or if separation is good enough, only one phase will burn.
Just one phase being burnt is in NO way indicative that the voltage regulator has a problem, nor is it an indication that the voltage regulator doesn't.
Reducing the radiant heat directed at the stator cover can't hurt and should help, but I doubt it will help all that much.
No body is measuring the stators temperature but only the cover temperature and through various means. The stator is mostly hanging inside there and not in particularly good contact with the cover.
What would be REALLY interesting is if someone attached a thermocouple to the stator and read off temperatures. Hell, could add a gauge to the cluster and monitor it full time. "I ride a BMW, stator temperature is more important then coolant or oil pressure lol"
But seriously, I have a cheap digital candy thermometer. The sort u get at a grocery store. As it happens, It dropped into some carmel I was making and while I was tearing apart the kitchen looking for it, my carmel turned into hard candy. While chipping it out of the pan I found my digital candy thermometer but broken in half. The thermocouple, wire and display head all came out and still works. The wires are tiny and would squeeze under the rubber plug on the cover, RTV the junction to the magnet wire, tape the head to the cover and we would have real temperatures.
I.m in St Louis if anyone wants to come by and experiment :)
Owned to date. Honda Aero 50, Honda Elite 80, Honda Elite 250x2, Suzuki Katana, Suzuki RF600, Yamaha YZF1000R, Kymco Xciting 500, Suzuki GS500, Suzuki Burgman 650, BMW F800GSx2, BMW S1000RR, Aprilia Scarabeo 200, Aprilia Caponord, Aprilia Sportcity 250
I love and miss you Jeneca and I'm sorry.