Heat sinks respectively carrying the positive pole pole diodes and negative pole diodes of a three-phase rectifier are assembled with their diodes and with screw studs and the free diode leads are soldered to strips connecting conjugate diodes to which socket contacts are soldered in the middle of the respective strips before the whole assembly is flooded with a resin, pressed and allowed to harden into an integral unit. Leads from the generator windings are soldered into the socket contacts and the rectifier assembly is mounted inside an end-bell of the generator by means of the screw studs of the rectifier unit. In a modified construction a screw stud affixed to the positive heat sink is set in a depression of the heat sink plate and insulated therefrom by a bushing.