What’s the difference between a GE AC4400CW and a AC4400CW-CTE? I guess a AC4400CW-CTE is a AC4400CW with some changes, and I think UP is only railroad that has the AC4400CW-CTE. Both types are listed on UP’s roster.
Dunno the details, but it seems the CTE (controlled tractive effort) units can be set to limit themselves to 110,000 lb tractive effort-- which would mean full power down to maybe 14 mph, then more and more derating as speed dropped further.
Eastward on Donner Pass they often run trains with two CTEs on the rear-- on regular freights the timetable doesn’t allow paired AC44s to shove unless one? both? are set to CTE.
A AC4400CW-CTE has different control software, mechanically they are identical. The software limits the amount of tractive effort when the CTE function is switched on, to 110,000 lns TE. The CTE function is switched on only when the locomotive is used as a DPU helper on a non-bulk train. The reason for this is that the full maximum TE available is likely to push lightly loaded freight cars off the rails on curves. The 110,000 lbs. TE figure was chosen because it is the same amount as produced by a Dash-9 (DC Motored locomotive). When the AC4400CW-CTE is used on loaded bulk unit trains it is allowed to produce the full 180,000 lbs. of TE, as the heavy (286,000 lbs weight) of the cars will keep them planted on the rails.
There is a CTE version of the ES44AC also. GE’s DC motored locomotives do not need CTE software as their maximum TE is low enough not to cause problems with normal DPU placement rules. Of course sooner or later someone screws up and puts light weight cars like empty TOFC or other flatcars too close to the DPUs and bad things happen.
Maximum TE for two units, you mean? Or do some RRs not allow even one AC to shove with full TE?
Yes, for 2 units. If both units are AC units, then both must be in CTE mode.