Yes, they are three phase.
I know what a traction motor is and where it is. Someone want to take a minute and explain the rest to me?
I would appreciate it.
Mookie
She who has no signature! cinscocom-tmw
and that is the 3 phases?
Evidently I knew that, just didn't know the terminology.
Thanx
Mooks,
Three Phase refers to how the main generator generates electricity. There are three seperate windings in the generator. Each is off-set by 120 degrees from the other. Consequently, if you look at the sine waves that they produce when they reverse polarity, they'll be out of step with each other by 120 degrees.
Three phase power has some distinct advantages in applications like large motors (traction motors for example). Perhaps Randy can fill us in on the details, but I believe that the rotating magnetic field produced in three phase motors is preferable for starting and accelerating.
Hopefully that explains it a little bit. It's been awhile since I dealt with any of this, so any filler and corrections would be appreciated.
-ChrisWest Chicago, ILChristopher May Fine Art Photography"In wisdom gathered over time I have found that every experience is a form of exploration." ~Ansel Adams
Mookie wrote:I think I have it... And the railroads have gone mostly to AC currently (sorry...). Do they still even make new locomotives with DC say within the major 5?
Never too old to have a happy childhood!
....J: Those traction motors also have another duty to perform ....Downgrade, will find them turning into generators {electrically}, and become "brakes" in simple terms, to help to keep the train {speed}, under control.
Quentin
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
tree68 wrote:The careful (fully electronic) control of the AC to the traction motors is what allows an AC locomotive to crawl along at single digit speeds in notch 8. That would fry a DC motor.
It's that crawling part that raises some questions.
From an industrial engineering prof:
"The story we read about the AC motors on diesels is that, while more expensive than DC motors, the latest designs seem to cope better with very demanding loads at very low speeds than do DC motors. In a nutshell, they enable fewer diesel locomotive units on a train, albeit operating at slower train speeds. The operations opportunity: one can feasibly handle a heavier load while running more slowly if diesels are equipped with AC motors. The contemporary switch to AC motors was driven by the Powder River Coal business and BN management in particular. Powering of their coal trains evolved from 5 3,000 HP DC units to 3 4,000 HP AC units. Train speeds slowed down (and so car cycles stretched out somewhat and therefore freight car costs went up), but locomotive and fuel costs per trip went down."Knowing what I know about railroad management costing systems, I suspect the profit gain from this change was overestimated. I suspect the profits lost from slowing down all the trains, particularly on lines with mixed traffic, were underestimated."
Intentionally planning a lower operating speed -- and paying a higher price for that "ability" -- has a significant system cost penalty.
MichaelSol wrote: tree68 wrote:The careful (fully electronic) control of the AC to the traction motors is what allows an AC locomotive to crawl along at single digit speeds in notch 8. That would fry a DC motor.It's that crawling part that raises some questions.From an industrial engineering prof:"The story we read about the AC motors on diesels is that, while more expensive than DC motors, the latest designs seem to cope better with very demanding loads at very low speeds than do DC motors. In a nutshell, they enable fewer diesel locomotive units on a train, albeit operating at slower train speeds. The operations opportunity: one can feasibly handle a heavier load while running more slowly if diesels are equipped with AC motors. The contemporary switch to AC motors was driven by the Powder River Coal business and BN management in particular. Powering of their coal trains evolved from 5 3,000 HP DC units to 3 4,000 HP AC units. Train speeds slowed down (and so car cycles stretched out somewhat and therefore freight car costs went up), but locomotive and fuel costs per trip went down."Knowing what I know about railroad management costing systems, I suspect the profit gain from this change was overestimated. I suspect the profits lost from slowing down all the trains, particularly on lines with mixed traffic, were underestimated."Intentionally planning a lower operating speed -- and paying a higher price for that "ability" -- has a significant system cost penalty.
joemcspadden wrote:Michael--what you wrote and quoted above is certainly reflected in the philosophy of Norfolk Southern, which of course hauls a lot of coal over very demandingterrain. The only ac motors on the roster, as I understand it, are a few SD80-macsinherited from Conrail, and the word is they will be eliminating all of these as timegoes on.
That's interesting Joe, thanks for pointing that out.
I read comments like this above "I think I have it... And the railroads have gone mostly to AC currently (sorry...). Do they still even make new locomotives with DC say within the major 5?"
I wonder where these comments come from. My impression is that not only is DC the most popular traction motor, but that AC passed a sort of peak -- as railroads began to add in the collateral costs of operation based on experience.
By itself, the AC traction motor is a remarkably robust piece of engineering, heads and shoulders above the old DC traction motors I grew up with.
But the cost comparison is not located in the traction motor, it is located in the inverter, an expensive piece of additional electrical equipment, and based on my long-ago experience of pricing of inverters for railroad use and my current wondering of how any savings could justify the cost of those inverters, I am wondering how the overall investment can be justified since it is based on the AC advantages at very low speeds -- which not only incurs the additional cost of inverters, but increases overall system costs as well.
I would like to see some numbers ...
Michael - I live in BNSF territory and don't see DCs any more. And the power run-throughs that we see here are mostly AC. I know some of the smaller lines will run DC - probably because it is cheaper to purchase, but would the major railroads run AC since (I understand) that the speeds between point A and point D are usually traversed at the lower speeds.
If I was say - BNSF - I would spend the extra money for what I can get from an AC and make up the difference in another place. I think the advantages definitely outweigh the disadvantages - especially in this part of the country. I can't speak to NS since that is a part of the country I have never visited.
Mookie wrote:Michael - I live in BNSF territory and don't see DCs any more. And the power run-throughs that we see here are mostly AC. I know some of the smaller lines will run DC - probably because it is cheaper to purchase, but would the major railroads run AC since (I understand) that the speeds between point A and point D are usually traversed at the lower speeds. If I was say - BNSF - I would spend the extra money for what I can get from an AC and make up the difference in another place. I think the advantages definitely outweigh the disadvantages - especially in this part of the country. I can't speak to NS since that is a part of the country I have never visited.
Mookie wrote:So Joe, why did NS go with DC and BNSF seems to have gone with AC? I must be missing something here.
joemcspadden wrote:I don't believe there is a "right" or "wrong" in either case.Regard, Joe
I don't believe there is a "right" or "wrong" in either case.Regard, Joe
Maybe the more appropriate term would be "best fit?" And that would be an internal decision based on numerous factors.
It's all in the application.
MS mentions speeds - it's possible that BNSF needs the low speed pulling capability enough that it's worth their while - perhaps cheaper in the long run than maintaining/using pushers. Possible scenario - hard pull out of a valley followed by relatively flat running. The speeds would average out.
NS may opt to put more power on to raise the minimum train speed (a necessity with DC anyhow).
Too, we can't really have a meaningful discussion without looking at things like average train length/weight and overall grades.
tree68 wrote: It's all in the application. MS mentions speeds - it's possible that BNSF needs the low speed pulling capability enough that it's worth their while - perhaps cheaper in the long run than maintaining/using pushers. Possible scenario - hard pull out of a valley followed by relatively flat running. The speeds would average out.NS may opt to put more power on to raise the minimum train speed (a necessity with DC anyhow).Too, we can't really have a meaningful discussion without looking at things like average train length/weight and overall grades.
Maybe you shouldn't give NS too much credit!
About 10 years ago, I asked an NS middle-to-upper level Mech Dept staff guy, "Why no ACs?" The main reason was that "NS ran mostly two units per trains, so no unit replacement benefit with AC". As it turns out, that really isn't a true statement. There are lots of applications on ACs would give good unit replacement ratios while still keeping HP/ton at required levels. I suspect the truth was that the Mech Dept couldn't be bothered to do the training and the hassle of keeping the fleet segregated was more than anyone wanted to take on, and now there's a lot of inertia and, perhaps some crow to eat if ACs were to be purchased.
I think some of this same "logic" is the reason NS has derated 4400 HP locomotives....
...and which RR was last to dieselize, and which RR was last to purchase GP9s, etc, etc.
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
oltmannd wrote: tree68 wrote: It's all in the application. MS mentions speeds - it's possible that BNSF needs the low speed pulling capability enough that it's worth their while - perhaps cheaper in the long run than maintaining/using pushers. Possible scenario - hard pull out of a valley followed by relatively flat running. The speeds would average out.NS may opt to put more power on to raise the minimum train speed (a necessity with DC anyhow).Too, we can't really have a meaningful discussion without looking at things like average train length/weight and overall grades. Maybe you shouldn't give NS too much credit! About 10 years ago, I asked an NS middle-to-upper level Mech Dept staff guy, "Why no ACs?" The main reason was that "NS ran mostly two units per trains, so no unit replacement benefit with AC". As it turns out, that really isn't a true statement. There are lots of applications on ACs would give good unit replacement ratios while still keeping HP/ton at required levels. I suspect the truth was that the Mech Dept couldn't be bothered to do the training and the hassle of keeping the fleet segregated was more than anyone wanted to take on, and now there's a lot of inertia and, perhaps some crow to eat if ACs were to be purchased. I think some of this same "logic" is the reason NS has derated 4400 HP locomotives.......and which RR was last to dieselize, and which RR was last to purchase GP9s, etc, etc.
Mookie BNSF splits their orders between AC and DC locomotives. The new BNSF locomotives numbered in the 7xxx series are DC motored, while the new 6xxx series are AC motored. Currently I think the scorecard goes like this.
BNSF splitting between AC and DC
Only buying DC
CN and NS
Only buying AC
UP, CP, and KCS
Jury still out on CSX because they got into the same problem that UP did, the severe need to replace large numbers of older increasingly unreliable power as quickly as possible. Once UP accomplished that they went back to buying exclusively AC motored power. Indications that I have heard is that the ES44DCs have satisfied the urgent need for more reliable power on CSX and future orders will be for AC motored power only.
2006 Actual production by builder and railroad, note because this is actual production it doesn't match orders. Some orders partially built in 2005 or 2007.
BNSF GE 292 ES44AC locomotives
CN GE 35 ES44DC locomotives
EMD 5 SD70M-2 locomotives
CP GE 80 ES44AC locomotives
CSX GE 102 ES44DC locomotives
FEC EMD 4 SD70M-2 locomotives
FXE EMD 15 SD70ACe locomotives
GE 60 ES44AC locomotives
KCS EMD 5 SD70ACe locomotives
KCSM GE 22 ES44AC locomotives
NS EMD 76 SD70M-2 locomotives
GE 62 ES40DC locomotives
U P GE 100 ES44AC locomotives
EMD 100 SD70ACe locomotives
Totals AC 674
DC 284
The production for 2007 will be close to an even split, as BNSF and CSX are taking delivery of ES44DCs this year. In 2008 the balance is expected to swing back heavily to AC as both BNSF and CSX have large orders.
Mookie wrote: Michael - I live in BNSF territory and don't see DCs any more. And the power run-throughs that we see here are mostly AC.
Michael - I live in BNSF territory and don't see DCs any more. And the power run-throughs that we see here are mostly AC.
As best I can gather from the company magazines, through "iffy" tangential references, BN has about 1,000 AC locomotives, and 5,300 DC locomotives. The AC's appear to be almost entirely coal service, and recent purchases have been directed to that type because of the coal demand.
JayPotter wrote:One approach to justifying the cost of AC-traction is increased productivity expressed in terms of horsepower-per-ton. Exemplar numbers are contained on page 44 of the November 2006 issue of TRAINS.
For those that don't have that issue handy-- it just points out that 4400 hp AC GEs are rated for 2900 tons apiece up Cranberry, which is a lower hp-per-ton than their predecessors. Nothing beyond that.
Fascinating. I must take some time and digest all this good information!
timz wrote: For those that don't have that issue handy-- it just points out that 4400 hp AC GEs are rated for 2900 tons apiece up Cranberry, which is a lower hp-per-ton than their predecessors. Nothing beyond that.
For something beyond the basic numbers, you need to read the article. Its basic premise -- in the context of our discussion here -- is that a railroad will have a sufficient number of units in a given consist to produce enough horsepower to move its train at whatever speed is desired across its route; however if the railroad has to add even more units in order for the consist to produce enough tractive effort to keep the train from stalling on one or more short segments of that route, the railroad is probably wasting horsepower and should at least consider AC traction.
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