erikem 440 Hz??, That's one s-l-o-w IGBT if you're talking about the IGBT's switching frequency*. That does sound like a reasonable number for the highest synthesized output frequency (or switching frequency for a GTO thyristor). I would think the motor is more likely to choke on such a high frequency from core and eddy current losses in the frame and eddy current losses in the windings.Another factor limiting maximum motor speed on an AC drive is the voltage ratings of the IGBT's. The required voltage for an AC motor goes up roughly with motor speed (not fully true for the induction motors, but definitely true for synchronous motors). * The switching speed for an IGBT is limited by the "fall time", the time it takes for the emitter/collector current to drop 90% after the gate was turned off (typical ranges from a couple of hundred nanoseconds to one or two microseconds. For a short period of time, the IGBT is conducting nearly the peak current and holding off near peak voltage, the device is generating a lot of heat during those few hundred nanoseconds. The fall time can be reduced by reducing minority carrier lifetime, but usually at the expense of increased on-state voltage.
440 Hz??, That's one s-l-o-w IGBT if you're talking about the IGBT's switching frequency*. That does sound like a reasonable number for the highest synthesized output frequency (or switching frequency for a GTO thyristor). I would think the motor is more likely to choke on such a high frequency from core and eddy current losses in the frame and eddy current losses in the windings.
Another factor limiting maximum motor speed on an AC drive is the voltage ratings of the IGBT's. The required voltage for an AC motor goes up roughly with motor speed (not fully true for the induction motors, but definitely true for synchronous motors).
* The switching speed for an IGBT is limited by the "fall time", the time it takes for the emitter/collector current to drop 90% after the gate was turned off (typical ranges from a couple of hundred nanoseconds to one or two microseconds. For a short period of time, the IGBT is conducting nearly the peak current and holding off near peak voltage, the device is generating a lot of heat during those few hundred nanoseconds. The fall time can be reduced by reducing minority carrier lifetime, but usually at the expense of increased on-state voltage.
Sorry, that is the limit of output for the GTO powered inverters in a SD70MAC.
As far as the power rating for IGBTs, Siemens, Bombardier, and Alstom all have IGBTs rated for 6kV. Skoda claims they will have similar capability in their new 109E series locomotives due this summer.
carnej1 BigJim agree, that's why we see the old geeps switching not the C30-7's. A six axel just isn't orented for switching tasks. Sometimes we see this however. A six axel locomotive is made to pull a long freight train over long distances, not to switch. I have heard engineers tell me no matter the kind of motor a six axel locomotive just isn't built for switching. You are constantaly moving the throttle from run 1 to idle. What a bunch of hoooey! Moving the throttle from run 1 to idle ain't switching Kid! That's pussyfootin'! First of all, there is nothing wrong with using a six axle to switch with...that is as long as it is a conventional six axle and not a Hi-Ad unit or a GE unit. THe Hi-Ad units ushered in an end an era of being able to switch up a storm. And forget about trying to swing a car by. They just don't respond fast enough. Conventional EMD six axle units do a good job and handle some tonnage to. And of course 6 axle units are often the preferred type of power for humpyard work...
BigJim agree, that's why we see the old geeps switching not the C30-7's. A six axel just isn't orented for switching tasks. Sometimes we see this however. A six axel locomotive is made to pull a long freight train over long distances, not to switch. I have heard engineers tell me no matter the kind of motor a six axel locomotive just isn't built for switching. You are constantaly moving the throttle from run 1 to idle. What a bunch of hoooey! Moving the throttle from run 1 to idle ain't switching Kid! That's pussyfootin'! First of all, there is nothing wrong with using a six axle to switch with...that is as long as it is a conventional six axle and not a Hi-Ad unit or a GE unit. THe Hi-Ad units ushered in an end an era of being able to switch up a storm. And forget about trying to swing a car by. They just don't respond fast enough. Conventional EMD six axle units do a good job and handle some tonnage to.
agree, that's why we see the old geeps switching not the C30-7's. A six axel just isn't orented for switching tasks. Sometimes we see this however. A six axel locomotive is made to pull a long freight train over long distances, not to switch. I have heard engineers tell me no matter the kind of motor a six axel locomotive just isn't built for switching. You are constantaly moving the throttle from run 1 to idle.
And of course 6 axle units are often the preferred type of power for humpyard work...
A EMD unit can handle more too I guess. I hope I didn't offendyou guy's. Sorry if I did.
.
Tugboat Tony Close... the reason you don't see any GE's switching is that they are incredably slow to load. listen and watch the next time you watch a train start with EMD's and GE's (be sure to stay back from flying pistons and oil from the toaster) sorry just had to throw that in there. The EMD's go to a full field much faster than a GE. it's been true since they started building their own road units. the 2 cycle engines also rev much much faster. As for AC vs DC. it seems to have been analyzed to death. AC is better for PERFORMANCE than a DC. but unless you really really need the drag power a DC is much much cheaper, but requires much more maintance. ( tend to be a little more reliable though; maybe it;s because we don't have many DC GE's left)
Close... the reason you don't see any GE's switching is that they are incredably slow to load. listen and watch the next time you watch a train start with EMD's and GE's (be sure to stay back from flying pistons and oil from the toaster) sorry just had to throw that in there. The EMD's go to a full field much faster than a GE. it's been true since they started building their own road units. the 2 cycle engines also rev much much faster. As for AC vs DC. it seems to have been analyzed to death. AC is better for PERFORMANCE than a DC. but unless you really really need the drag power a DC is much much cheaper, but requires much more maintance. ( tend to be a little more reliable though; maybe it;s because we don't have many DC GE's left)
es go to a full field mean?Load, I've heard that term before what does it mean? What is the flying pistons mean? What happens when a locomotive goes to full field? Thanks.
The road to to success is always under construction. _____________________________________________________________________________ When the going gets tough, the tough use duct tape.
"I Often Dream of Trains"-From the Album of the Same Name by Robyn Hitchcock
Wll I didn't say you couldn't switch with a six axel, as already stated railroad's switch with six axels all the time. So the Hi-aid truck isn't fast enough so when you throtlle up it doesn't imediately start to move like an EMD? A EMD unit can handle more too I guess. I hope I didn't offendyou guy's. Sorry if I did. Did I tell you one day I want to be a locomotie engineer for NS?
beaulieuCould you please explain what you are trying to say? AC motored locomotives have no trouble operating at around 1 mph for continuous loading at mines. There is a maximum practical limit for how fast the the IGBTs can cycle, roughly 440 Hz, which as modified by gearing affects the top speed, you could lower the gearing for improved slow speed operation.
Could you please explain what you are trying to say? AC motored locomotives have no trouble operating at around 1 mph for continuous loading at mines. There is a maximum practical limit for how fast the the IGBTs can cycle, roughly 440 Hz, which as modified by gearing affects the top speed, you could lower the gearing for improved slow speed operation.
carnej1 bubbajustin I agree, that's why we see the old geeps switching not the C30-7's. A six axel just isn't orented for switching tasks. Sometimes we see this however. A six axel locomotive is made to pull a long freight train over long distances, not to switch. The bottom line is that AC is mutch more expensive than a DC motor. Untill thay come down on price some railroads just won't buy them. Nice to see a locomotive that is AC in a SWITCHER configuration. So ror the JSRR (Justin Sandlin Railroad) Look's like wele be sticking with DC traction. Maby when the price comes down. Note that 6 out of 7 Class 1 RR's in the US/Canada have bought AC's with CN being the sole holdout so far.Some of those roads have split orders recently between AC and DC for different types of service. There are some regional RR's that have bought new DC power but regionals generally buy "used" anyway. AC electrical equipment is more expensive than DC equipment(and may always be) but the AC drive units perform better and have lower maintenance and fuel costs in many (BUT NOT ALL) applications.
bubbajustin I agree, that's why we see the old geeps switching not the C30-7's. A six axel just isn't orented for switching tasks. Sometimes we see this however. A six axel locomotive is made to pull a long freight train over long distances, not to switch. The bottom line is that AC is mutch more expensive than a DC motor. Untill thay come down on price some railroads just won't buy them. Nice to see a locomotive that is AC in a SWITCHER configuration. So ror the JSRR (Justin Sandlin Railroad) Look's like wele be sticking with DC traction. Maby when the price comes down.
I agree, that's why we see the old geeps switching not the C30-7's. A six axel just isn't orented for switching tasks. Sometimes we see this however. A six axel locomotive is made to pull a long freight train over long distances, not to switch. The bottom line is that AC is mutch more expensive than a DC motor. Untill thay come down on price some railroads just won't buy them. Nice to see a locomotive that is AC in a SWITCHER configuration. So ror the JSRR (Justin Sandlin Railroad) Look's like wele be sticking with DC traction. Maby when the price comes down.
Note that 6 out of 7 Class 1 RR's in the US/Canada have bought AC's with CN being the sole holdout so far.Some of those roads have split orders recently between AC and DC for different types of service. There are some regional RR's that have bought new DC power but regionals generally buy "used" anyway. AC electrical equipment is more expensive than DC equipment(and may always be) but the AC drive units perform better and have lower maintenance and fuel costs in many (BUT NOT ALL) applications.
Oh yah, I guess that NS did enter the 21st century and buy the ES44AC. I wish I had something moer inteligant to say. I just try to absorb as mutch info as I can. Ac is still more expensive but I think we still might see evan CN buy some AC's in the future. It seems from what you guy's are telling me that AC is more efficiant in some apps.
trainfan1221 I have seen six axle power, even new ones in some cases, doing switching duties. A railroad may not buy these or an AC locomotive for that actual purpose but once they are on the property who says they can't if thats what is needed at a particular time? I remember seeing, some years back, Conrail using two SD50-60 type locomotives switching a job usually done by one GP38. I guess its what happens at the time. As someone pointed out on another thread, there is always a possibility of anything happening on a railroad at any given time.
I have seen six axle power, even new ones in some cases, doing switching duties. A railroad may not buy these or an AC locomotive for that actual purpose but once they are on the property who says they can't if thats what is needed at a particular time? I remember seeing, some years back, Conrail using two SD50-60 type locomotives switching a job usually done by one GP38. I guess its what happens at the time. As someone pointed out on another thread, there is always a possibility of anything happening on a railroad at any given time.
Yah, it's just whaever the railroad has on hand at the time. I have heard engineers tell me no matter the kind of motor a six axel locomotive just isn't built for switching. You are constantaly moving the throttle from run 1 to idle.
bubbajustinSo what you are saying is that the AC models produce too mutch power for the low-speed switching.
Not true...... There are several manufacturers in Europe bulding diesel electric switchers with AC traction motors. Republic Locomotive in South Carolina is marketing a 500 HP industrial switcher with AC propulsion which supposedly has the same pulling power as a 1000 HP EMD SW unit. A 4300HP -4400 HP locomotive would be wasted in switching duty whether it's AC or DC drive (which is not to say that they are never used in that capacity).
JonathanSThe speed of the AC locomotives is controlled by the frequency of the AC produced by the electronics. There is a practical lower limit which causes the lowest speed of the ACs to be higher than you would want for switching. That problem will likely be corrected, but at least for the moment ACs are very poor switchers.
The speed of the AC locomotives is controlled by the frequency of the AC produced by the electronics. There is a practical lower limit which causes the lowest speed of the ACs to be higher than you would want for switching. That problem will likely be corrected, but at least for the moment ACs are very poor switchers.
Could you please explain what you are trying to say? AC motored locomotives have no trouble operating at around 1 mph for continuous loading at mines. There is a maximum practical limit for how fast the the IGBTs can cycle, roughly 440 Hz, which as modified by gearing affects the top speed, you could lower the gearing for improved slow speed operation. A reason that current AC locomotives are not good switch engines is that they are slower to accelerate, intentionally, so as not to create excessive in-train forces when they are used in road service. If it were intended to use them in switching service the software could be modified. As AC motored locomotives are expensive, it is not economic to assign them to switching service, of course sometimes you have to use whatever locomotive is available. AC motored switch locomotives are not uncommon in Europe, albeit they are not as popular as hydraulic transmissions.
Oh I get it now!!! Duh. Anyway, the AC motors are very expensive shurly thay will come down, my math teacher buoght his first calculator for $500, now you can go tho the Dollar Tree and get one for 50 cents. What keep's an AC motor from over-haeating.
I don't know what Big Jim means by that but ok.
NS tested some AC units years ago and found that for what little extra tonnage they could haul in the rain did not equate to the huge difference in price over a DC loco. Keep in mind, that was then and this is now.
I've run both and the most impressive thing about an AC unit is their dynamic brake and not what it will pull!
Big Jim was just pointing out that you spelled "which" wrong. But indeed AC is the way of the future. Some railroads like to keep standardized, so they stick with traditional DC power. As Lyon pointed out, this might change.
Hi all,
Thank's for the replies. I don't know what Big Jim means by that but ok. How or what keep's a AC motor from over heating vs. a DC motor? Wat happens when a motor overheats? So depending n the type of trais, the weight and my RR's budget, onlt 10 bucks a month That will determine what locomotive I should buy. Ok that makes sence.
I think the only reason DC freight locos are still being built is they’re still cheaper than AC-traction. If AC reaches price parity with DC, interest for new 6 axle DC will dry up. Even holdouts NS and CN will migrate to AC if there’s no price penalty.
The technology to finely-control AC traction motors only became practical in the last 20-25 years, and affordable in the last 10-15 years. To call it 'affordable' is a stretch--it is still an accounting question whether your use of the locomotive can afford the extra cost of the AC motors which can cost 30% to 50% higher than the all-things-being-equal DC model.
In the transit world it has become very affordable, enough even so that not only are all new DC Metro cars ordered with AC motors, the refurbished DC cars are furbished with AC motors.
This is a very ignorant question but witch motor is the best?
Glenda, the good witch!
The AC Motor is better not just because it is more resistant to overheating, but also because you can achieve a higher factor of adhesion (more pulling power). The big question is will the AC locomotive give you a better return on invested money. Simply put you would look at the AC locomotive and the equivalent DC locomotive study the trains that your railroad moves and decide if the AC locomotive can move your trains more efficiently, and if it can how much money could it save your railroad in a year, and over the lifetime of the locomotive. Then you look at the price difference between the AC and the DC locomotives, and figure out what the money saved by buying the DC motored locomotive could earn for you. How that comparison comes out will determine whether you should buy the AC or the DC locomotive.
This is a very ignorant question but witch motor is the best? I mean I know that An AC motor will run way out there without over heating, I don't know how but, anyway. A DC motor will over heat if pushed over the limit. So it would seem that the AC motor is the best right? But what if I'm the president of the Justin Sandlin Railroad Co. I operate in Indiana hauling corn and serving little facories and towns. should my RR choose an AC motor or DC motor? It's very flat will either be best suited for the terrian? AC is more expensive, will it give me the bang for the buck? Witch will cost me the least in the long run? Will It be cost effective for me to order AC locomotives say an ES44AC to pull my type of trains? Just some things to think about. Ps, don't mean to start a war between the AC lover's and the DC lover's.
Our community is FREE to join. To participate you must either login or register for an account.