edbenton The only Class one I was aware of that Reduced the HP on the ES44 was NS theirs are considered ES40's I asked a engineer for the BNSF helps I live right next to the BNSF connection track with the NS and be amazed what information you can get for a big cup of hot Coffee. He flat out told me that the BNSF Evos are all rated for 4400 HP and will not be reduced in power. Also he has heard that they are getting 100 more of the ES44AC4's evidently they love them and will be using them on any and all trains except coal.
The only Class one I was aware of that Reduced the HP on the ES44 was NS theirs are considered ES40's I asked a engineer for the BNSF helps I live right next to the BNSF connection track with the NS and be amazed what information you can get for a big cup of hot Coffee. He flat out told me that the BNSF Evos are all rated for 4400 HP and will not be reduced in power. Also he has heard that they are getting 100 more of the ES44AC4's evidently they love them and will be using them on any and all trains except coal.
CSX is derating all of its GE DC locomotives to 4000hp.
An "expensive model collector"
Tugboat Tony carnej1 IIRC, NS ES44ACs are being delivered without the electronic derating feature and operate at the full 4400 HP. They are primarily for coal drag service and NS tests showed that having full HP was a plus for that application when using AC traction. NS fleet of ES40DCs and C40-9s have a switchable engine output control. They normally operate at 4000 HP but supervisors have a key which switches the locomotive to 4400 HP.... I HIGHLY doubt that. even if the railroad supervisors had the ability to increase the HP there would never be one rated at 4000 HP if nore was available. I would believe that GE had the software necessary to uprate the units should the railroad decide to. By the way... as a forum newbie, what does IIRC stand for?
carnej1 IIRC, NS ES44ACs are being delivered without the electronic derating feature and operate at the full 4400 HP. They are primarily for coal drag service and NS tests showed that having full HP was a plus for that application when using AC traction. NS fleet of ES40DCs and C40-9s have a switchable engine output control. They normally operate at 4000 HP but supervisors have a key which switches the locomotive to 4400 HP....
IIRC, NS ES44ACs are being delivered without the electronic derating feature and operate at the full 4400 HP. They are primarily for coal drag service and NS tests showed that having full HP was a plus for that application when using AC traction. NS fleet of ES40DCs and C40-9s have a switchable engine output control. They normally operate at 4000 HP but supervisors have a key which switches the locomotive to 4400 HP....
I HIGHLY doubt that. even if the railroad supervisors had the ability to increase the HP there would never be one rated at 4000 HP if nore was available. I would believe that GE had the software necessary to uprate the units should the railroad decide to.
By the way... as a forum newbie, what does IIRC stand for?
IIIRC=If I recall correctly.........The information about the NS units has been widely reported on various forums and publications including postings by NS engine service employees. The keys are in the possession of Road Foremen who are under standing orders to leave the locomotives at the lower ratings(to control fuel consumption) unless the higher HP rating is needed in specific service.......
"I Often Dream of Trains"-From the Album of the Same Name by Robyn Hitchcock
"If I recall correctly".
JayPotterCould you please define "slip speed"?
Could you please define "slip speed"?
Slip speed is the difference between the synchronous speed and the actual rotational speed of an induction motor. For example, a four pole motor running on 60 Hz will have a synchronous speed of 1800 rpm, but will be typically spec'ed at 1725 rpm, for a difference of 75 rpm. This slip of 75 rpm is what causes current to be induced (hence "induction") in the rotor bars and the interaction of the induced current and the rotating magnetic field produced by the stator windings is what produces the torque.
If you try spinning the shaft of an induction motor faster than the synchronous speed, the "motor" will generate an opposing torque and become an induction generator.
A decent, but not perfect, analogy is a fluid clutch or torque converter (without the torque multiplication).
Hope this helps.
- Erik
CP's AC4400CWs and ES44ACs have software that limits power output at full throttle to 4000hp. at speeds above 28 mph. Below that speed throttle position 8 will cause the diesel to produce 4400hp. (well 4390hp. if you want to be precise).
erikemAnother way of putting it is that peak torque occurs at a high slip speed with high resistance and a low slip speed with low resistance. With a variable frequency drive, the motor can be designed with a low resistance motor, and to get good starting torque, the drive operates at a low enough frequency that the slip speed is less than the slip speed that gives peak torque (you always want some torque headroom).
With a variable frequency drive, the motor can be designed with a low resistance motor, and to get good starting torque, the drive operates at a low enough frequency that the slip speed is less than the slip speed that gives peak torque (you always want some torque headroom).
Thank you.
daveklepperMy understanding is that most ac traction motors currently in use are not true synchronous motors completely dependent on the input electrical frequency for speed control.
My understanding is that most ac traction motors currently in use are not true synchronous motors completely dependent on the input electrical frequency for speed control.
As of 2005, GE was using induction motors for their AC diesel electric locomotives (from a talk given at our company shortly after we were bought by GE, we're now a joint venture with Safran Group) and I would be very surprised if EMD was not using induction motors in their AC diesel electrics. These motors are presumably squirrel cage motors, quite possibly with the slanted rotor bars. Anyway, one of the subjects of the talk was GE's research into permanent magnet synchronous motors which would give about 25% more torque for a given motor frame than an induction motor and better efficiency at high tractive efforts (no waste from the eddy currents in the rotor bars).
One problem with squirrel cage motors was that, assuming a constant line frequency, they could be designed for high efficiency and low starting torque (low resistance bars) or high starting torque and reduced efficiency (high resistance bars). The wound rotor was a way of having the best of both worlds, using high resistance to get the starting torque and low resistance once the motor came up to running speed. Another way of putting it is that peak torque occurs at a high slip speed with high resistance and a low slip speed with low resistance.
With a variable frequency drive, the motor can be designed with a low resistance motor, and to get good starting torque, the drive operates at a low enough frequency that the slip speed is less than the slip speed that gives peak torque (you always want some torque headroom). This removes the need for the variable rotor resistance provided by the wound rotor induction motor.
One other advantage of the low resistance rotor design is that the resulting motor torque changes very rapidly as a function of speed for a given drive frequency. Any wheelslip will cause the motor to speed up and the torque will drop.
Did someone in another thread mention that DC traction motors were limited to about 1000HP per axel? ACs do not have that limitation?
Thank you all for the responses. I didn't know this kind of traction system could be so interesting.
Will
Awesome! Lyon_WonderI think the only Class 1s that are ordering DC 4000-4400hp 6-axle GE and EMD locos are CN, NS, and BNSF, though BNSF has a large AC-traction fleet too. UP, CSX, KCS and CP have seem to gone exclusively with AC with recent orders. Mostly DC-traction NS has a handful of former-CR SD80MACs and 24 ES44ACs, while CN has no AC-traction whatsoever. Even regional Class 2s IAIS and MRL have AC-traction on their rosters. And the Indiana RR now has SD9043MACs too. BNSF has covert their ES44AC to 4,000HP from 4,400.
Lyon_WonderI think the only Class 1s that are ordering DC 4000-4400hp 6-axle GE and EMD locos are CN, NS, and BNSF, though BNSF has a large AC-traction fleet too. UP, CSX, KCS and CP have seem to gone exclusively with AC with recent orders. Mostly DC-traction NS has a handful of former-CR SD80MACs and 24 ES44ACs, while CN has no AC-traction whatsoever. Even regional Class 2s IAIS and MRL have AC-traction on their rosters. And the Indiana RR now has SD9043MACs too.
BNSF has covert their ES44AC to 4,000HP from 4,400.
Really? I'm aware that some of UP's GEVO fleet has a software system that reduces tractive effort when the units are used in DPU mode but I didn't think they had derated the whole fleet...
My understanding is that most ac traction motors currently in use are not true synchronous motors completely dependent on the input electrical frequency for speed control. The dissadvantage of such motors is that an instant overload where there is insufficient torque means loss of all power. What I have been told (and correct me if I am wrong) is that they are "hysterises non-synchronous" motors. The operating principle is pretty much the same, but the difference in construction is that the rotor bars are not perfectly horizontal but are slanted, all parallel of course, but not at right angles to the direction of motion and not parallel with the rotor shaft.
The great advantage over wound rotors is huge ability for high thermal overload allowing short-time overload ratings to be longer in time and larger. This and the absence of brushes associated with both dc motors and ac-commutator motors (GG-1, EF-3, etc.) drastically reduces maintenance requirements.
tdmidgetHas the wound rotor and its rotor current limiting device been made superfluous by solid state electronic controls?
Has the wound rotor and its rotor current limiting device been made superfluous by solid state electronic controls?
Yes.
The advantage of a wound rotor motor was that it would give both high starting torque and high running efficiency for operating at a fixed line frequency. The disadvantages are that it is heavier, more expensive and less rugged than a squirrel cage motor.
With a variable voltage variable frequency drive, the drive frequency can be set low enough to ensure good starting torque (peak torque is a function of slip frequency for a given motor design).
After searching Google for AC traction motor- images, I'm surprised. What i saw was nothing more than a squirrel cage induction motor, although with a rather massive shaft. I expected a wound rotor motor, which I had been told was in use in Europe. Has the wound rotor and its rotor current limiting device been made superfluous by solid state electronic controls?
Thank you all for the great responses.
owlsroost wholeman Do you think AC will be the only thing available in the future? Yes - it's already happened in Europe - as far as I know, the big rolling stock suppliers on this side of the pond (e.g. Bombardier/Alstom/Siemens) only offer AC traction on their light rail/EMU/locomotive/HSR products. I'm sure EMD & GE are only continuing to build DC equipment because some US/Canadian railroads still want to buy it, not because they believe it has a long-term sales future. Tony
wholeman Do you think AC will be the only thing available in the future?
Do you think AC will be the only thing available in the future?
Yes - it's already happened in Europe - as far as I know, the big rolling stock suppliers on this side of the pond (e.g. Bombardier/Alstom/Siemens) only offer AC traction on their light rail/EMU/locomotive/HSR products.
I'm sure EMD & GE are only continuing to build DC equipment because some US/Canadian railroads still want to buy it, not because they believe it has a long-term sales future.
Tony
GE has been implying of late that they would like to only offer AC power, the new A-1-A 4 motored ES44ACs for BNSF are being touted as a replacement for 6 motored DC units..
owlsroost I'm sure EMD & GE are only continuing to build DC equipment because some US/Canadian railroads still want to buy it, not because they believe it has a long-term sales future. Tony
Could it be that the tax situation in the US and Canada (CNRR esp) is different than Europe.? Probably ACs will increase in price less than DCs. There also could be a sudden closing the price gap if some component(s) becomes much cheaper . Maybe when the price of AC locomotives gets to a certain point closer to DC locos then all RRs will order all AC lcomotives? At that point the remaining DCs will slowly become orphans with the DC specific item costs gradually esculating faster than the other loco costs. Have no idea what this year's awful winter snows will do to future equipment decisions? May come to the point where in winter DCs will be sent to south away from snow storms.
wholemanDo you think AC will be the only thing available in the future?
CSSHEGEWISCH The Chicago Transit Authority is also beginning to go with AC traction motors, some other transit operations may be doing the same thing.
The Chicago Transit Authority is also beginning to go with AC traction motors, some other transit operations may be doing the same thing.
That seems to be a good idea for CTA since they do have some winters with a lot of snow.
CSSHEGEWISCHThe Chicago Transit Authority is also beginning to go with AC traction motors, some other transit operations may be doing the same thing.
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
Some advantages noted are a comparsion of AEM-7DCs vs AEM-7ACs. To meet AMTRAK acceleration specifications for the NEC; they usually limit DCs to 7 - 8 cars and ACs to 10 cars.
But as mention in the above post the abilty to seal the motor is the most important one. The thread about the CAL Z problems of running in the snow and having ground faults on the DC locos is very important. As a CEO of any RR that operates in snow country I would want all my trains to operate in snow without grounding out. The severe winterwe are having maybe many RRs will change their orders to AC and order a much higher percentage of ACs. The reduction of inverter costs may also be a factor?
I suspect that the cost of high power inverters will continue to decline. Current state of the art are IGBT inverters with induction motors, 5 to 10 years down the line we may be seeing GaN or SiC FET's driving permanent magnet synchronous motors. The new FET's should result is smaller inverters due to faster switching times leading to less heat being dissipated in the active devices. A permanent magnet synchronous motor can produce at least 25% more torque for a given frame size than an induction motor, as well as being more efficient at low speed high tractive effort conditions. Cooling will be even simpler than with the induction motor as very little energy will be dissipated in the rotor - it might be simplest just to use water cooling.
The following are the advantages:
1. No commutator or brushes to need maintenance.
2. If the pinion breaks or something, the motor will essentially continue on at its current speed instead of over revving and blowing apart (birdcaging).
3. Easier to seal and cool the motor.
4. More horsepower and torque is possible from a given volume of motor. Traction motor space is very limited.
5. More precise control of drive wheel speed which can increase available tractive effort.
6. The motors themselves are actually simpler and less expensive with only two bearings and one moving part.
The main disadvantages are:
1. More complex electrical and electronics gear with inverters and so on.
2. More cost because of the extra cost of the drives.
IMHO, DC drive technology is very mature without much room to grow. AC drive technology is much more open to expansion. As the cost of the drives comes down it is likely that AC drives will become more predominant, especially on heavy mainline locomotives. Current high horsepower variable frequency drives (inverters) are about 1/10 the cost they were 15 years ago.
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