Electric generators types depend on the type of generating equipment employed, the electrical energy produced is either direct current (DC) or alternating current (AC).
AC generators are classified as single-phase or polyphase. A single-phase generator is usually limited to 25 kW or less and generates AC power at a specific utilization voltage. Polyphase generators produce two or more alternating voltages (usually two, three, or six phases).
DC generators are classified as either shunt, series, or compound-wound. Most DC are the compound-wound type. Shunt generators are usually used as battery chargers and as exciters for AC generators. Series generators are sometimes used for street lights. The emf induced in a DC generator coil is alternating. Rectification is needed to direct the flow of current in one direction. The generator rotating commutator provides the rectifying action.
References: “Joint Departments of the Army and the Navy, Operation Maintenance and Repair of Auxiliary Generators, 26 August 1996”
