jzeeff, I have two single phase ST alternators and I have used both at some time. The first one I tried ran very cool (only a few degrees above ambient) and was only taken out of service due to bearing failure and a "clunking" sound when turned over slowly. The second alternator ran much hotter. I do not recall the actual numbers now but it was noticeably hotter - maybe 20 - 30 degrees C hotter than ambient.
jens, now I have gone to 3 phase, I assume the ripple in the full wave bridge rectified DC output to be within the stated <10% specification of the SMA inverter, so I simply take this DC and plug it straight into the inverter (no filter caps, no batteries, etc). I run the Listeroid at 540 RPM and the STC at around 1500 RPM (50 Hz here in UK) with the field rheostat turned right down so I see about 530 volts DC cold, unloaded (about 520 volts DC warm, unloaded) and around 495 - 505 volts DC, loaded.
I hope this helps.
Regards,
Ian