I have an automotive (3-phase) alternator with peak rated output of 150A at 14V (after rectification, of course). How can I determine phase (AC) currents in this situation?
Determine the current in one leg of a three phase generator based upon DC output after 3 phase rectifier. (Assuming current in each phase is the same).
Disregarding losses in the rectifier diodes : The power that goes in must equal the power that comes out.
Power in from 3 phase alternator =\$\sqrt3* Vph * Iph\$ where \$Iph\$ is current in one leg (phase).
Power out of DC rectifier = \$.95*\sqrt2 * Vph * Idc\$
Use the .95 for now because Peak voltage = \$Vdc = \sqrt2 *Vph\$ . Has to do with ripple and other things in the DC output.
Equating the power in and power out (equal to each other), and solving for \$Iph\$
\$Iph = .775 * Idc\$
So your "peak rated output of 150A" becomes \$Iph = 116.25\$ amps.
Not an exact solution but very very close hopefully for your needs.
EDIT : corrected minor math error in final Iph and mulitiplication