What is used as the rectifier to produce direct current in a DC alternator?

• A. Brushes and a commutator.
• B. Six solid-state diodes.
• C. A rotary converter.
• D. A mechanical relay.

Answer: (D)

A DC alternator uses a rectifier made of solid-state diodes to convert the produced AC into DC. In a typical three-phase alternator, the stator windings generate three-phase AC, and a diode bridge rectifies it. This bridge uses six diodes—three connected to the positive output and three to the negative—so each phase’s half-cycle is converted to current in a single direction. The result is DC that can be used by the electrical system, with the diodes preventing reverse flow and smoothing the output compared to a simple single-phase arrangement. This solid-state rectification replaces a mechanical commutator, offering reliable, high-current DC with less sparking. The rectifier diodes are built to handle the machine’s current and heat and are housed in a rectifier assembly integrated into the alternator.