This is something that I have been observing for a while in american engines. I took the CN as example for the pics but it happens also with CSX ones. While already accelerating when throttle is set to higher notches the generator pauses, goes to 0 and then revs up to higher amps again. Is this any kind of series to parallel transition or a bug? You can also notice how the locomotive gains tractive power on the camera motion sway effect when generator works at high amps again. I used the HUD for better spotting. Cheers
Because I'm lazy, here's a cut-and-paste from Wiki. Short version- it's the electric equivalent of shifting gears: __________________________________________________ "As the locomotive accelerates, the now-rotating motor armatures will start to generate a counter-electromotive force (back EMF, meaning the motors are also trying to act as generators), which will oppose the output of the main generator and cause traction motor current to decrease. Main generator voltage will correspondingly increase in an attempt to maintain motor power, but will eventually reach a plateau. At this point, the locomotive will essentially cease to accelerate, unless on a downgrade. Since this plateau will usually be reached at a speed substantially less than the maximum that may be desired, something must be done to change the drive characteristics to allow continued acceleration. This change is referred to as "transition", a process that is analogous to shifting gears in an automobile. Transition methods include: Series / Parallel or "motor transition". Initially, pairs of motors are connected in series across the main generator. At higher speed, motors are reconnected in parallel across the main generator. "Field shunting", "field diverting", or "weak fielding". Resistance is connected in parallel with the motor field. This has the effect of increasing the armature current, producing a corresponding increase in motor torque and speed. Generator / rectifier transition Reconnecting the two separate internal main generator stator windings of two rectifiers from parallel to series to increase the output voltage. In older locomotives, it was necessary for the engine driver to manually execute transition by use of a separate control. As an aid to performing transition at the right time, the load meter (an indicator that shows the engine driver how much current is being drawn by the traction motors) was calibrated to indicate at which points forward or backward transition should take place. Automatic transition was subsequently developed to produce better-operating efficiency and to protect the main generator and traction motors from overloading from improper transition." ____________________________________________________ Note that the throttle positions on the Bakerloo Tube are actually named "Shunt," "Series" and "Parallel"
