Industrial Power Plant, what are these components?

[sasilverbullet]

I was at a old power plant today and there was this old diesel powered generator.

Please help solve what the two "generators" hooked to it are specifically for.

There's a large one, and a smaller one at the end of the shaft.

What is the big generator for?
What is the smaller one for?

 

[69GTX]

Big generator for supplying plant power....smaller one on the shaft a field flashing generator? Our 10 MW Delaval Turbine Generator had a small field flashing generator attached to the end of it. That was built in the later 1980's.

 

[Nyogtha]

Dunno in a power plant, but the small thing could be a motor to slow roll the assembly on startup from dead stop. In my industry we had small steam turbines sharing the shaft of large steam turbines sometimes, with the small turbine just used for startups.

 

[Lou_Boyle]

I would guess that the large generator is the AC power generator and the smaller one is a DC generator that provides excitation power to the field windings of the AC generator.

 

[Shannow]

Just rotary excitation, as others have suggested.

The 500MW Parsons/Erith machines had multiple stages of rotary exciter...small one to excite the main exciter and that made the magnetic field on the generator rotor, to drive the AC in the three phase stator.

Modern machines have "static" excitation, where the job is done through massive thyristor banks.