That is the unilateral phase detractor. It prevents sinusoidal depleneration of the lunar wane shaft.

Pilot and main exciter, plus an overspeed trip switch. Pilot excites the main, main excites the field windings. Mechanical overspeed switches are usually set to 10% over in case the generator breaker opens during normal generation usage.

Here's my guess. The assembly on top is a small generator used to produce power for the exciter field of the main generator. The slip rings are to bring in a small amount of outside power to energize the exciter of the small generator during startup. The mercury switch is operated by centrifugal force. After a certain RPM is reached it disconnects the external power source and the entire main generator and exciter/generator can operate independently. Its sort of a bootstrap operation.

My guess is the exciter that cuts on once the generator hits about 75% rated speed. Works similar to an alternator I imagine giving out dc power to increase the field strength in the main generator.

small slip rings connect to centrifugal overspeed device contact that trips unit offline under overspeed condition . external Rheostat (or static pilot exciter) controls exciter field strength to stationary field windings mounted around inside of exciter frame . Exciter field flux cuts through exciter armature windings rotated by generator shaft producing DC current then fed through carbon brushes and applied to main generator field poles mounted on Gen rotor. Main field poles magnetic flux then cuts though Gen stator windings as rotor turns producing Generator terminal volage .

This is exciter. Nowadays power electronics are used to supply DC electricity to field windings. But old Alternators still use small DC generators which are connected to the same shaft, to excite to the field.

The separate coils and the commutator make up the direct current exciter, probably around 110v DC and 70 to 90 amps most likely based on load. The big slip rings will be for the actual field in the alternator, DC in, exciter coils induce AC in the stationary windings of the alternator. I am not however sure what the small set of rings is for, however the mercury switch might be for speed reference, the rings go with it.

Hmm, "Site 3 still has all this". Something which has been outmoded or can be replaced by something simpler or more modern. Has a mercury switch, so it is only in operation at startup or only after startup. Has both AC and DC aspects, commutator handles high power. Topically, somewhat related to recent discussions. I'm going to guess it is a self-regulating, self startup system from a time when the generator was an isolated power station without grid ties. How it might work in one of those roles is something I have to ponder. Lol, commutator gonna be noisy as frig, though, electrically speaking.

DC generator (I see interpoles in there, similar to the traction motors we work with) which generates DC which (via control gear to regulate output) is then put on the two big slip rings to excite the rotor. The small slip rings above and the mercury switch is for overspeed cut out. Modernised machines would dispense with the whole lot and just retain the large slip rings with DC excitation current coming from a separate rectifier and overspeed sensor by laser or servo.

Okay, I'm going to take a guess. The mercury switch is an oscillation sensor. I don't know if it's tuned to a resonance, I kind of doubt it because the massive inertia of the generator is probably at a much lower frequency, but the angle at which is mounted suggests that it probably detects excessive travel both in the rotation plane as well as the rotational axis. The slip-ring commutator reminds me of a universal motor, so I'm thinking it's more like a universal generator that generates a noisy DC voltage at some pretty decent power, and being coupled to the shaft, it seems like it's a pretty good candidate for feeding power to the exciter. Probably some other stuff too, like maybe feedback for the wicket gate control to keep it trimmed to a steady output. As a generator, it would need input to an exciter stator, which I suspect comes from the top two slip rings. There would still need to be a DC supply to get it started which would be a right bitch if the grid feed was down. I suppose if the grid has failed, that's a whole other barrel of donkeys. That whole control system is a case study in itself. You've got exciter voltage (power), blade angle, wicket gate flow, and probably stuff I'm missing. I'm gonna guess it supplies power to the exciter and probably the actuators for the controls.

Likely a DC generator for the field windings of the generator, tilt switch for indicating speed limit of the shaft

That is the exciter, which is a small generator attached to the end of the larger generator. It provides the dc field current to the rotor. As all generators produce ac the commutator acts as a rotating switch changing the current path when sine wave changes polarity to rectify the output. Just my guess.

If I had to take a guess, maybe it's a motor to speed up or slow down the generator by tiny amounts to get the right frequency output (match the mains)? Gotta get the light nice and synchronized on that dial that goes spinny spin spin.

The reason it has comutator bars and slip rings is because it requires dc to energize the field winding. Unlike some household generators where it's just a slip ring, you need to have excitation in the field winding to generate any electricity. This also has the added benefit of being able to change the field winding excitation to govern output voltage, wheras a household generator is typically fixed.

I think it's a DC generator for the main generator excitation used because it wasn't economical or efficient to rectify the AC voltage

Well the mercury switch at that angle detects threshold speed (centrifugal force). The commutator must be a motor to oppose the generator below to either speed up or slow down.

Must be exciter rings and the switch is a safety trip to prevent the generator from being damaged if it gets into a out of sync condition

Late to the party, ex navy nuke here. We used to have these on the USS Enterprise (CVN-65) but dammit I’ve forgotten the technical name for them! Everyone saying it’s the dc generator for the field is, I think, correct? My guess for the mercury has nothing to do with overspeed, rather it enables the field once the generator reaches sufficient rpm.

Exciter stator/rotor and overspeed switch!

DC generator to excite rotor windings plus start windings?

For the field reference exciting voltage feedback loop

my guess. pilot exciter and main exciter... the commutator is to turn an AC sin wave into pulsed DC. this creates and controls voltage to the main electro-magnets in the rotor. the switch is to cut power to the exciter until the generator reaches a certain RPM?

Possibly an automatic governor that cuts the power going to the exciter?

My wild ass guess is a small generator to power the exciter on the main generator in a black start scenario. Maybe the mercury switch cuts it off once the main generator is spinning fast enough to self excite.

The exciter? Switch is probably some centrifugal switch so it kicks in at a certain speed.

Top exciter with murcury switch cut out.

Knowing the exciter is DC, and the age of Big M, and the exciter power WAS adhock into the pabel that got replaced..... that's the DC generator to make the power to get Big M excited way back when. I doubt the grid bIg M fed had a supply other than herself when ahe was built. Likely a few years later the Grid was more connected, n didn't need ti rely on self exciting.

Commutator. What they used to get DC before proper rectifiers?

The mercury switch is the overspeed cut out.

Speed regulation with inner pole current

It uses external power to excite the generator until it reaches a high enough speed to self excite at which point the mercury switch disconnects external power and its self exciting from that point on...similar to an older style car alternator...that's my guess...now I'll watch the next video to see how immensely wrong I am 😂

Sparkly and effervescent 😂😂😂

I assume an exciter or prime mover for start up

gives power for the wikket gates ???

Exciter and PMG is my guess

it's a HUGE variable transformer.

I think i know what it is ... A lot of copper? Its basically just a big motor

starting motor!

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I just read the whole disclaimer. I don't think it was worth my time

Exciter

dc generator/motor

Exciter