Rockies climb throttle position question

[zephyr17]

I see what you mean. He said "engines," which is what threw me off. I think with AC motors it wouldn't be a problem, but I bet these have DC. ACs can pretty much take whatever you throw at them.

All Amtrak's current diesels have DC traction motors. Amtrak doesn't need the low speed heavy pull capacity that freight engines do that AC traction motors provide. They did have a some AC units in the 90s that were kind of testing the concept for passenger use. I don't recall the actual model designation, but the railfan slang name for them was "winnebagos" because the front end kinda of looked like an RV's. I am pretty sure they were EMD products.

I don't know the costs involved but speculate there is a price difference that at least partly drove the decision on DC versus AC traction motor.

 

[Cal]

All Amtrak's current diesels have DC traction motors.

I thought Chargers had AC motors?

 

[JLChicago]

All Amtrak's current diesels have DC traction motors. Amtrak doesn't need the low speed heavy pull capacity that freight engines do that AC traction motors provide. They did have a some AC units in the 90s that were kind of testing the concept for passenger use. I don't recall the actual model designation, but the railfan slang name for them was "winnebagos" because the front end kinda of looked like an RV's. I am pretty sure they were EMD products.

I don't know the costs involved but speculate there is a price difference that at least partly drove the decision on DC versus AC traction motor.

I think it’s more along the lines of Amtrak not wanting to modernize. The CTA wanted DC motors for their trains and were told by manufacturers that no one wanted to bid on outdated equipment. So they went AC.

Metra just recently bought used SD70MAC (AC) locos and seem to be having success with them.

Alaska RR is using similar locos.

I can’t see any advantage to DC in this day and age. It’s really obsolete tech. Any upfront capital cost savings is eaten up and then some by increased operating costs.

 

[jis]

I thought Chargers had AC motors?

They do have Siemens 3Phase AC Induction Motors.

 

[cirdan]

It may not have been the prime mover which overheated. The electrical drive system also is prone to heating up, especially when run at high power and slow speeds. I have an F3 manual from the bad old days with an ammeter chart showing the limits of what the traction motors could take. The system is different now, but I-squared-R is still the same.

Indeed. Do you know if the traction motors are self ventilated? This could make low speeds a problem.