Towing of locomotives and cars with electric motors

[jeffmorris]

Do railroad staff have to prepare locomotives and cars with electric motors for towing? I think that if railroad staff doesn't prepare locomotives and cars with electric motors for towing, the motors will become generators.

 

[kws4000]

Do railroad staff have to prepare locomotives and cars with electric motors for towing? I think that if railroad staff doesn't prepare locomotives and cars with electric motors for towing, the motors will become generators.

On most (afaik) American DEs, you simply turn the "Selector Switch" from "Run - Lead/Run - Trailing" to "Isolation". All it does is disconnect all controls and power cables and turns the loco into a 150-ton paperweight. Brakes still function like a freight car.

Electrically speaking, if there is no resistance attached to the motors (ie dynamics), then the motors simply spin. All they do is add a little bit more inertia to the train when rolling. If the dynamics were attached, then yes indeed there would be a braking force.

 

[Pendolino]

Electrically speaking, if there is no resistance attached to the motors (ie dynamics), then the motors simply spin. All they do is add a little bit more inertia to the train when rolling. If the dynamics were attached, then yes indeed there would be a braking force.

If the excitation winding is not energised, the motors would not work as generators, as their rotors would not rotate inside a magnetic field.

 

[DeRiCo]

I saw what can happen once when a dead diesel was being shunted.

It was being pulled out of the roundhouse onto the turntable, but someone had left the battery switch in, and the reverser in forward.

As the loco was pulled out backwards 5 wheels were rotating normal, but one wheel was trying to go the other way.

Even at about 2kph the 5 motors were generating enough power to spin the other motor in the opposite direction.

Could cause a lot of damage to that wheel if it was to happen on the main at higher speeds.

Dennis