ES44DC and ES44AC question

[denveroutlaws06]

is true you have to have the DC unit on point over a AC unit?

[eagle1030]

Nooooo.  I've seen plenty of trains with only AC power.  Where did you pick this up?

[denveroutlaws06]

i was just trying to confim what the text said in this picture was true for all others Railroads companys, and yes i know trains can run just AC units i was just wondering if AC and DC were mixed in toghter.

http://www.coloradorailfan.com/gallery/photo.asp?id=103630

[eagle1030]

Hmm.  Never heard of that policy before.  Then again, I don't know that many policies.  I do believe that this is peculiar to BNSF.  Here in UP territory, AC or DC can lead.  I believe on CSX, NS, CP, or CN (if you can even find an AC unit) it doesn't matter either.

I'm wondering on the thinking behind this.  How would an ES44AC burn out an ES44DC's traction motors?

[eagle1030]

eagle1030

I'm wondering on the thinking behind this.  How would an ES44AC burn out an ES44DC's traction motors?

Never mind.  Found this link http://www.trainorders.com/discussion/read.php?1,1381672 (don't know how to directly link yet, sorry).

In summary, only DC traction motors can burn out.  In the cab of an AC unit, the engineer may be pushing his DC units too far and burn out the motors without realizing it.

So why only BNSF?

[guetem1]

that is correct, on BNSF we generally do not mix AC and DC power, unless it is an emergency situation requiring replacement power off the first train that comes by.  But the reason stated above is correct AC power can grind it down to barely moving without damage to the traction motors, that would be asking to fry a set of DC motors (anything under about 7 mph is asking for trouble)

[beaulieu]

The computers controlling modern DC motored locomotives have Motor Thermal Protection whereby the computer calculates the probable temperature  based upon motor amperage, ambient air temperature, and time. With this information the computer will derate the locomotive output to prevent the traction motors from burning up. Of course if you have older DC power in the consist like a SD40-2, then the Engineer has to be careful about the traction motors.

Mixed consists are becoming quite common.

[johnwvan]

I checked the loco consists in my recent pictures data log and found these three right off:

BNSF 9217 SD70ACe                UP 8648 SD70ACe                   BNSF 5691 AC4400CW

BNSF 8841 SD70MAC                UP 4181 SD70M                       BNSF 1062 C44-9W     

BNSF 5949 ES44AC                  UP 4702 SD70M                        BNSF 5459 C44-9W

BNSF 4374 C44-9W

Looks like in practice BNSF and UP don't really care too much.

[Phelps]

This is correct, but motor thermal protection is relatively new.  The most vulnerable part of a DC traction motor is and always has been the commutator, and "stall burns", lifted commutator bars, and the like are almost a given if too much current for too long is applied at very low speeds.  The AC motor doesn't care whether it's rotating or not; just keep the cooling air coming, and it will be fine.

 

Dave Phelps

[EMD#1]

Yes it is true, however not everyone is aware of the rule as evidenced by some mechanical and transportation forces when assembling a set. The higher amperage developed by AC traction can burn out DC traction motors in extreme working conditions such as starting heavy tonnage trains on a grade.

Tim G.

NS Locomotive Engineer

[pamelapeterson]

Good Morning,

i'm a novice at this railroad stuff but it does fascinate me.

Your post/reply shows several different locomotives. Two(2) questions come to mind;

How can someone determine by the locomotive designation whether it has an AC or DC traction motor???

Also, how can someone determine the locomotive type(SD70, AC4400,etc,etc,...) by the road number???

Thanx for allowing me to visit and post a message...

iBob

[M636C]

pamelapeterson

How can someone determine by the locomotive designation whether it has an AC or DC traction motor???

In general, the model number of a locomotive with AC traction motors includes the letters "AC"

In the example in the thread title, ES44 has suffixes AC or DC depending on the type of motor.

The preceding GE models were "Dash9-44CW" for the DC version but "AC4400CW"  for AC version.

Current EMD locomotives are SD70M-2 (DC) and SD70ACe (AC).

The preceding generation codes were SD70M (DC) and SD70MAC (AC)

It isn't as clear with passenger locomotives but most dual mode (electric 3rd Rail + diesel) have AC motors.

So GE P40 and P42 are DC while P32 DM is AC. The EMD DM30AC is also AC traction.

Earlier generations of locomotive were almost always DC.

pamelapeterson

Also, how can someone determine the locomotive type(SD70, AC4400,etc,etc,...) by the road number???

 

The only way is to check a railroad roster where locomotive models and road numbers are listed.

These are available on line and can be found by googling "Union Pacific Locomotive Roster" for example.

 

Most railroads do paint the model number on the cab side near the number (in pretty small type) but this can often be read in photos.

 

UP sadly sometimes uses a description of their own, so an ES44AC will be listed as a C45ACCTE....

 

M636C

[carnej1]

pamelapeterson

Good Morning,

i'm a novice at this railroad stuff but it does fascinate me.

Your post/reply shows several different locomotives. Two(2) questions come to mind;

How can someone determine by the locomotive designation whether it has an AC or DC traction motor???

Also, how can someone determine the locomotive type(SD70, AC4400,etc,etc,...) by the road number???

Thanx for allowing me to visit and post a message...

iBob

Are you asking how to identify locomotives as a railfan or how operating crews working for the railroads identify the power they are assigned?