I believe on the Dash 8's you could change a screen (there were three, two for the engineer and one for the fireman (helper)) to show TM amps. With the Dash 8, there are protections in place so that as traction motor thermal limits are reached, the motor amperage is capped. This changes. For example, in low ambient temp conditions the TM cooling air is colder and the motors have more thermal capability. Similar for altitude, where denser cooler air is available near sea level. Tunnel operation is another variable, depending of course on the length of the tunnel. Staring with the Dash 8, GE introduced several new features. For example, if a motor goes to ground, there is no or truck TM disconnect switch, the control system will isolate that motor and provide a msg to the operator. The system will even detect and try to dry out a moisture ground anywhere in the motor or braking system by passing a nominal current through it.
I am amused by the MTH ad that states that the SD70 has the piping on one side of the platform and the cabling on the opposite side to aid maintenance. GE has done this "forever", starting with the U25B in 1963.....
Re operation using units with differing MCS (minimum continuous speeds), I remember when the PRR operated an E7 or E8 equipped passenger train into Erie, as Trains 580 and 581. That train was always assigned an Alco RS3 helper to get out of the lake basin and south. The RS3 helper engineer burned up a number of traction motors on the two unit "E"'s on one winter trip with the single RS3 in lead, and local management rode several trips to "reacquaint" the helper crew with the limitations of passenger power on grades. The local volunteer fire department gained considerable publicity as a result of this problem. Once you leave Erie and are about three miles south of town, it gets pretty rural.....
