In the Class 66, if I maintain a throttle notch for a long enough period of time, the locomotive seems to cut traction power. Reducing power and slowly building back up works every time to keep the train moving. I'm wondering if this is some kind of overload or overheat protection built into the Class 66. Is that the case?
The Class 66 does a transition at about 35mph where the traction motors have to switch from running in series to running in parallel as the locos speed increases. Power has to be cut for this to happen. However the engine does not throttle down it just has the load placed upon it by the generator reduced and then reapplied. English built diesel-electric locos work slightly differently and have what is called field diverts instead. Someone will be able to explain it much better than I can. But it is prototypical behaviour.
