Old Breakers
Old Breakers
I think those large black switches with the horizontal handles are actually circuit breakers. There are three dash pot trip units under each breaker with a linkage up to the trip element. The dash pot provides the time overcurrent time delay and a solenoid does the instantaneous trip. It's been about 30 years since I had a chance to work on one of those. The arc chutes are very rudimentary which makes it interesting when the breaker trips as you are standing in front of it.
The last ones I worked on were at a steel mill feeding a bank of parallel 250VDC rectifiers for bridge crane power. The instantaneous trips would drop all the breakers open when multiple cranes started lifting. Maintenance had to run to the switchyard and reset the breakers. This happened 2-3 times a month.
The owner requested we defeat the instantaneous trips, assuming they were worn out. All feeders to the rectifiers were short, open bus runs terminating on the rectifier input fuses and the upstream protection looked adequate for protection, so we complied and tye-wrapped the armature flappers in place. Next time the cranes' heavy loads coincided, all the input fuses blew and the cranes were down for a day while they searched for enough replacement fuses. They cut the tye-wraps on the instantaneous trips and went back to five minute outages. (If I knew then what I know now?.)
So the old breakers did work. Just wear ear protection when in the area.