Yeah, that occurred to me too. But they may have been using shore power. If they test those motors under full load as part of the qualification procedure, those mains could have sourced many megawatts steady-state without too much complaint.
Looking at the pictures, it's obvious that the rotor was locked. One set of commutator bars is completely melted. Adjacent bars are coated with flash products but not themselves melted. Quite a lot of copper — by which I mean pounds of it— appears to have been vaporized.
The only other possibility I can think of (and this goes beyond my knowledge of large motors) is that perhaps they somehow managed to energize forward and reversing circuitry at the same time. I say that because it looks like the current actually travelled laterally, from end to end, the long way, through the commutator bars. All the brush holders are smoked, and the carbon brushes appear to have burned away. Perhaps half the brushes are used for forward and half for reverse... that seems a bit old fashioned, but who knows how old these propulsion plants are. They mentioned "boilers" in one of the stories, which indicates they're kind of long in the tooth.
If they had actually put full voltage to the motor with the rotor locked, one would expect that the rotor windings corresponding to the energized commutator bars would also be melted, or at least have been heated to red hot. That would have severely damaged the rotor itself and the adjacent windings. No such damage is shown in the pictures or mentioned by the story's "sources." In that case, I would thin we'd be looking at a lot more than a commutator rebuild.
Once you let the magical smoke out of electrical devices, they never work again. (^;
Yup. Putting new smoke back into a motor with a six-foot diameter commutator would cost some real money, I'm guessing.
It seems like they would just reverse polarity to reverse rotation.
I think you are correct, the commutator was locked and they forgot that fact when they went back online.
I have never worked with motors anywhere near that size bit did get to see the results years ago of what happens when you bring a hydroelectric generator online extremely out of phase with the grid.
Buddy of mine bought a new truck with some of the overtime he got.
Yeah, I'll say.
Is there no such thing as a brushless (i.e. electronically commutated) motor at this scale? This is basically diesel-electric we're talking about? I Imagine the electronic controller would cost huge $$$ but would be far more efficient in the long run.
Where did you find pictures? I was hoping for photos, but the linked article had none...