Thanks for all the suggestions guys.
We used to use hi pots all the time but the U.P. pretty much phased them out around here much to my disgust. They were a good tool for finding hard to find grounds in cabling but I guess the railroad was afraid someone was going to get shocked into cardiac arrest. Also, we've really fried some computers good by not isolating things the way they should have been.
Railroad Forums
SW1500 Aux Gen. Overcharging.
- General discussion about locomotives, rolling stock, and equipment
Moderator: John_Perkowski
No, Dutchrailnut is wrong. During operation the ground relay only protects the high voltage system. When starting, the low voltage and high voltage systems are connected so a low-voltage ground shows up by tripping GR.
It can be a bear to track one down, especially if it's a negative because they are all daisy-chained together. But it's a necessary task. Grounds are not only a no-no to the FRA man, but get the wrong ones and all sorts of things can happen. Years ago a crew climbed off some ALCO Centuries on the D&H at Mechanicville. They failed to center the reverser or open Gen Field. Something went to ground, connected with a ground already there, and the units went to 8th notch and roared up the yard into a cut of cars. The independent brake was no match for wide-open locos.
Results are not always that drastic but an on-the-ball mechanic will take the time to track it down. The lazy or incompetent ones will jump out the GR, which is about like putting a penny in the fuse box!
It can be a bear to track one down, especially if it's a negative because they are all daisy-chained together. But it's a necessary task. Grounds are not only a no-no to the FRA man, but get the wrong ones and all sorts of things can happen. Years ago a crew climbed off some ALCO Centuries on the D&H at Mechanicville. They failed to center the reverser or open Gen Field. Something went to ground, connected with a ground already there, and the units went to 8th notch and roared up the yard into a cut of cars. The independent brake was no match for wide-open locos.
Results are not always that drastic but an on-the-ball mechanic will take the time to track it down. The lazy or incompetent ones will jump out the GR, which is about like putting a penny in the fuse box!
The ground on the unit is the key to the issue because through generator action the rotating armature is inducing magnetism into the start winding while the engine is rotating (I have a charcoal 3/8 ratchet to prove it). I don't remember if the negative side of the start winding is isolated by the contactor or not. The start winding ground & a set of relay contacts welded together could do this (main or Aux). ..... My kingdom for a musty, greasy old print !!!