Alternators & Excitation
The alternator converts the engine’s mechanical power into electrical output. On a brushless set it comprises a main stator and rotor, an exciter, a rotating rectifier assembly and — on PMG machines — a permanent magnet generator. Bearings, diodes and surge suppressors are the usual wear items.
Almost every generating set above a few kVA uses a brushless synchronous alternator. Output is controlled by varying exciter field current, which means the alternator, the AVR and the rotating rectifier behave as one system when diagnosing a fault.
Frame size is quoted with the winding number — a UCI 274 with winding 06, for example. Both are needed to identify bearings, diode sets and terminal arrangements correctly.
Parts in this system
1 reference listed. Prices quoted on enquiry.
Common questions
What does the alternator frame number mean?
The frame designates the physical size and core length of the machine, and the winding number that follows it defines the connection and voltage range. A UCI 274C and a UCI 274D share a frame family but differ in core length and output, so parts are not always common between them.
How often should alternator bearings be replaced?
Typical practice is replacement at overhaul or between 20,000 and 30,000 running hours, whichever comes first, though duty cycle and ambient conditions shorten that considerably in dusty or high-temperature installations.
Related systems
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