rdunniii posted:Hot Water posted:The GN Man posted:Interesting thread, especially Jack's notes above...
My understanding of the Alaska RR SD70MACs in passenger service (4300-series) is that internal switching disconnects the rear traction inverter from the rear truck traction motors and this inverter then provides 480V 3-phase HEP to the train. This locomotive then has just its forward truck powered, so ARR usually has a second unit in the consist to provide adequate traction for the train. When the unit is in freight service, or another HEP source is available, then all six axles are powered.
I am wondering if the METRA SD70MACs will be the same, or if they found a way to squeeze in an additional inverter for the HEP while keeping all traction motors operative?
According to what I've read elsewhere, this "new", i.e. completely re-manufactured units, will have 6 inverters: 4 for traction (there would thus be only 4 AC traction motors), and 2 for HEP.
Soooo, maybe they are becoming like the current C4 variants (either A1A or B1)?
And METRA stipulated in the article they will meet Tier III requirements.
Since the trucks are 3 axle, the traction motors will be mounted on the first 2 axles within each truck, providing an AAR powered wheel arrangement of A-A-1 1-A-A. Remember that E Units were A-1-A A-1-A, with the unpowered "idler" in the center position. With the HTC-R "Radial" truck, the "idler" will be on the end, or inboard position.
