Still some sort of big error in your calculation-- 100000 lb TE won’t accelerate an 1100-ton train at 1.6 mph/sec, even with zero rolling resistance.
If we assume traditional Davis resistance, then train resistance in pounds is A + BV + (C times V squared) where V is speed in miles/hour and
A = 3653.5
B = 33.45
C = 1.0344
That’s assuming 125 US tons for the engine-- zat right?
And you’re assuming 7338-2/3 rail horsepower at all speeds, except a 100000-lb TE ceiling up to 27.52 mph. Tonnage 1115 actual and I’ll guess 1159 effective inertial tons (the increase for rotational inertia).
The 18 cars are 1530 ft long; in that distance the train accelerates to 40.37 mph in 48.5 seconds. The standing-start mile takes 97.75 seconds; speed 61.6 mph at that point.
Five miles takes 273.8 seconds; speed there 96.1 mph; it reaches 100 mph in 31688 ft and 310.5 seconds. After ten miles they’re at 109.7 mph.
In reality the train won’t accelerate to 40 mph in its own length-- none of us knows what it could do if the engineer didn’t bother starting smoothly.
Traditional-Davis says the train needs 2763 rail horsepower to maintain 80 mph. Think it actually needs less than that?
Quoting overmod: “Just what an ‘input inverter’ that feeds a ‘DC link’ might be is a mystery. I suspect they meant ‘rectifier’ in this context (see here for an example feeding a motor directly) … but got lost in translation without a proofreader who understood the technology.”
You really need a copy editor who understands the technology; a copy editor has the authority to make changes in text; a proofreader only ascertains that what is going to be printed is what the author wrote and has no authority to correct the original manuscript/text (my wife worked in both capacities for two book publishers–and I gave her assistance when she was copy editing books that had mention of railkroads).
You are completely right. I think I was attributing fact checking to proofreading, but that’s no excuse. I would note in my own defense that when I proof galleys, fact checking is inherently part of the exercise; I don’t just limit it to correcting typographical mistakes.
Writer didn’t recognize (or perhaps didn’t care about) the difference, and editor didn’t or couldn’t catch it. Not a good thing all around for a technical publication… but then again I’m too much of a perfectionist when it comes to printed media…
No. (Assuming the period and damping of the secondary suspension is correct). The low unsprung mass, especially with respect to low inertia of the wheel in all axes of rail interaction, is far more significant for high speed.
Weight distribution across those four axles is of course important, and there might be a case made for ‘taper loading’ (a bit less weight on the outer axles) but at those speeds you will not have a problem with primary deflection, or (with any sensible type of track curvature and transition spiraling) high rates of lateral acceleration of heavier mass requiring sudden high flange forces. So the actual weight of the carbody is of less significance, up to the point the primary springing has to become too ‘hard’ to give short-period following of rail-level anomalies. (I do not think this is the case for 30-ton axle load, per se)
If you look at the Siemens drawing of the truck frame, the secondary suspension is four springs, arranged laterally (two and two) right on the lateral centerline of the truck frame. I presume the torque link is decoupled from the suspension (as it is for the Flexi-Floats) so there is no particular weight transfer on acceleration, and therefore no weird loading of the primary suspension.
I am presuming that Siemens knows where any critical speeds are, and has designed the truck masses and suspension characteristics accordingly.
An H-bridge inverter will gladly transfer power from the AC side to DC side (i.e. acting like a rectifier) as well as transferring power for the DC side to AC side (traditional inverter). In fact, many low output voltage (1V or less) DC-DC converters use FET’s operated as synchronous rectifiers instead of diodes, as it is easy to make the I*Rdson voltage drop less than the forward voltage drop of a diode. Having the inverter capability to feed regenerated power back to the catenary also saves in not having to carry the DB resistor grids around.
I would suspect that the there may be separate primary windings for the different voltage levels, though one way of handling 25Hz would be to use the same number of turns for 11kV/25Hz primary as for the 25kV/60Hz primary, but increase the number of secondary turns for 25Hz to maintain the same secondary voltage. This would result in about the same peak magnetic f
Has to be. C is what I had to vary to back into the performance. There is no published info I could find on a modified Davis Eq. for Amfleet.
I ignored the mass of the locomotive - which isn’t a terrible thing to do in the freight world, but matters a bit more here. I should add it in…it’s easy to do. Adding in rotational inertia? Meh. It’s less than passenger load (or my error in actual train weight) Let’s just call this a one and a half significant digit exercise!
Looks okay to me. But units are ft/s^2. No reason engineer can’t start a stretched train at that rate after a few seconds. It’s much slower than the 0.1g rate for some transit equipment.
Siemens are very good at providing technical detail on their website, often in English as well as German and circuit block diagrams are provided. The ACS-64 is basically a standard European locomotive adapted for Amtrak’s voltages.
Both input and output inverters are basically the same. The input inverters under power, as you imply, operate as rectifiers and feed their intermediate DC to the output inverters. Under power two of the output inverters feed the motors with variable voltage, variable frequency AC while the third provides 60Hz power at constant voltage to the train.
When in regenerative braking the “output” inverters take three phase power at variable voltage and frequency and convert it to DC which they feed to the “Input” inverters which convert it to single phase AC at the line voltage and frequency.
The input and output inverters are basically the same. The three output inverters are identical, and if the train HEP inverter fails, one of the traction inverters takes its place and the train proceeds on half traction power.
To address one point by the original poster, there are two major overhead line frequencies used in Europe, 50Hz (25kV) and16.66Hz (15kV). These are equivalent to the two voltages and frequencies used by Amtrak and many locomotives are built for the two AC systems. Generally, the transformer is built to take the lower frequency and will operate corr
I was hoping we could get you out from ‘under the wharf’ to address this!
Can you provide some specific URLs (in either English or German) that point to specific technical pages?
Also: a poster on one of the other lists (the PRR catenary electrics Yahoo group) had a detailed cut of the ACS64 truck, but didn’t provide any of the other information about its detail, particularly the way the torque linkage is arranged, or the specific routing of the shafts and gearboxes for final drive. Can you give us URLs that show truck mechanical detail, as well?
(As a partial defense: I was being a bit humorous about the ‘inverter feeding a DC link’ because of the way it was worded without comment. I thought it would have been more appropriate to say ‘inverter functioning as a rectifier’ (or something else similarly accurate at low word count). Same way I’d refer to the ‘speaker’ in a yard telephone when somebody is talking into it – not a microphone, of course, but acting as one. On the other hand, I easily lapse into pedanticism – hey, at least I recognize the problem!)
-Erik: One item that almost all of us including myself has posted is listing the change in voltage of the NYP - WASH 25 HZ system. Yes PRR started the system at 11Kv and upgraded to 11.5 Kv sometime after WW-2. Later sometime in Amtrak’s reign the voltage is now considered 12 Kv. All technical papers by Amtrak list the nominal voltage as 12 Kv. As to SEPTA I am not sure. These voltages enable the probable use of a center tap transformer that can accept 25 Kv 60 Hz, 12.5 Kv 60 Hz, & 12 Kv 25 Hz. BOS - NH is 25 Kv 60 Hz, NH - New Rochelle MNRR is 12.5 Kv 60 Hz, As well we now know Amtrak New Rochelle - Gate interlocking is 12.5 Kv 60 Hz, & the rest to WASH including Sunyside is 12 Kv 25 Hz. I suspect regenerative braking to the 25 Hz system is well within a 5 % tolerance. One other item; at present all equipment owned by Amtrak that has regenerative also has dynamic braking installed so whenever the CAT line voltage is too high the braking switches to dynamic from regenerative. That crossover voltage was specified at 13.4 Kv for Septa’S Silverliner - 5s. If and I say if these are the tolerances for for all three power sources then the ACS-64s can be buiol
Somebody said it was supposed to take 18 Amfleets zero to 125 mph in 8 miles? Lotsa luck.
The 0.045 is for freight cars-- it’s 0.03 for passenger.
If you drop a one-ton object off a tall building it will accelerate downward at 9.80665 meters per second per second, which is 21.937 mph/sec. In other words 2000 lb will accelerate a ton at 21.937 mph/sec-- so it takes 91.171 lb per ton to accelerate at 1 mph/sec, assuming no rotational inertia.
But you are saying 100000 lb tractive effort accelerates the 18-car train from 0 to 25 mph in 16.04 seconds? If so, your F doesn’t equal your m times your a. (Didn’t think it would take you this long to find your error.)
Turns out if we set the train’s resistance to zero (except for inertia) it will reach 125 mph in 7 miles from the start.
Inverters intended for variable speed drive with induction or synchronous motors are almost invariably variable voltage variable frequency. With that, the inverters should be able to handle a wide range of AC side voltages, though with a maximum set by the devices used in the inverter (this may be what sets the Silverliner 5’s 13.4 kV crossover). It is entirely possible, though not necessarily optimal, that the locomotives could operate without any tap changing on either the primary or secondary side (note that this is how the locomotives could be configured, not how they actually are configured).
One advantage of using the inverters on the catenary side of the DC link is that they can do power factor correction, i.e. that the current drawn is (mostly) sinusoidal and in phase with the voltage. Rectifiers generally induce rather non-sinusoidal currents, typically slightly trapezoidal square waves when choke input filters are used. Using thyristors to control the DC link voltage also introduces a significant phase difference between the voltage and current, with consequent reduction in power factor, where the inverter can control the DC link voltage and maintain unity power factor. Anything less than unity power factor requires more current to transmit the same power and thus more conductor area.
To my disappointment, Siemens have been progressively dumbing down their website, which was one of the last to give real technical detail and most of my sources just lead to broken links on Siemens’ website.
I might have some better data stored away somewhere…
I haven’t even been ON a wharf in some time. I’ve been trapped at a desk in our Navy Headquarters trying to get projects to meet certification requirements which is much less enjoyable.