New York subway system at one time or another was powered by similar setup my understanding during world war II this was highly protected piece of equipment, if someone were to throw sand into coils this would destroy everything.
It probably is something along those lines. Synchronous motors this size need a supplemental source of torque to get going up to speed before they can run sychrnonously, so I'd imagine what you can hear is the switch from start up to full synchronous motion.
It's driving a huge piston pump on the left side with about a 4 ft diameter crank and a piston about 2 ft in diameter. A smaller crank arm visible on the outside to the right is likely a slide valve. The large overhead cylinder at the back is a gas accumulator / bounce / buffer tank.
No a compressor doesn't need a synchronous motor, they are using the motor in two ways. This is a large factory by the look of it, they use the rotation of the motor to drive an air compressor to supply factory air, also by varying the rotor excitation, you can just see the copper slip rings near the wheel spokes, they can also correct the power factor of the factory so they reduce the factory line current. Another name for these motors is 'rotary synchronous condenser' Those old engineers were way smarter than they are credited.
@@jeffcarter4881 It looks like a single cylinder reciprocating compressor. I guess that explains the huge flywheel, to add momentum to the rotor of the motor, which is already huge!
