While not really relevant to the ACS-64, Vossloh have a circuit diagram in their “UK Light” diesel locomotive, fitted with a Caterpillar C175 engine.
The circuit diagram appears on the last page:
http://www.vossloh-innotrans.com/media/downloads/pdfs/vrv/Vossloh_UKLIGHT_us.pdf
In this case there is a rectifier on the alternator, but an inverter on the dynamic brakes.
It shows that the HEP inverters are basically similar to the traction inverters.
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From a copy of the ACS64 Familiarization and Orientation manual:
No weight given for the main transformer (which is between the trucks) but it is p/n A2V00002028490, and using that information might get you physical parameters.
It includes two 480VAC dedicated HEP transformers.
The two stepdown voltages for different catenary voltages are given as 1957 VAC and 1878 VAC, “depending on the catenary input”.
“Voltage switching Is Done Electronically By The Primary Side Tap Changer”
There is a modular “HEP Rack” (A2V00002106069) which produces 480 VAC “to locomotive as a secondary source of electricity … it can be used during full catenary line operation”. (This to me indicates that the inverter modules do not perform any HEP duty…)
The traction converters are A2V00002028491. The nominal DC link voltage is 3600 V nominal. Nothing is said about having HEP-compatible outputs in these converters.
I’m much more familiar with diesel electric locomotives with AC traction.
However, I understood that the Amtrak supply was 3 Phase AC 480 volts at 60Hz.
The overhead line supply is single phase AC at either 60Hz or 25Hz.
The only way of getting 3 phase AC from the OHL supply would be rectifying it and feeding it through an inverter.
If however the train only requires single phase 60Hz, transformers would suffice on 60Hz overhead but this would be unavailable under 25Hz supply.
Certainly the Amtrak P32s use an inverter for HEP supply and a traction inverter can be used in case of failure of the HEP inverter, the locomotive then running on three motors.
The Alaska Railroad SD70MAC can divert one inverter for HEP use on passenger trains with the remaining one powers the train.
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