Hot Water posted:Ted S posted:If the DC units were recent-production (in other words, not SD9's), I'm surprised they didn't have some kind of built-in protection that took the generator offline in the event of an overload.
Why would that surprise you? Neither EMD nor GE locomotives, "back in the day", such as SD40-2s and the like, are going to simply "shut down" in the middle of a long hard pull on a steep grade.
I've heard of the "short time rating." How hard would it be to incorporate a timer or a temperature sensor, which would allow the crew to use most or all of the short-time rating without catastrophic damage?
That would add more clap-trap stuff, which would need to maintained. Again, neither EMD nor GE designed their locomotives to "shut down" on a steep grade. For another example, when an EMD locomotive over-heated in a tunnel, the only thing that happens was; the "Hot Engine" alarm sounded, but the engine does NOT "shut Down".
In fact, when GE loco's DC traction motors started to overheat they would indeed start de-rating themselves to the point of stalling if you didn't stop first, put the unit in neutral and rev the engine up in eighth notch to get the T/M blowers going at full blast to cool the motors down. I have had the screen pulled up and watched this happen many times. As the T/M temp gauge went up above a certain point, you could see the HP rating start to drop. If you weren't right at the top of the hill where the lower power would get you over the hill, you had to stop and cool the traction motors before trying to get up the mountain again!
