One item not covered is how much additional weight does the dual frequency equipment carry.? We know that a 25 Hz / 60 Hz transformer is heavier than a stand alone 60 Hz transformer weighs The regenerative braking equipment to provide the 25 / 60 Hz inverters would be very interesting. How fast the motor can go from power to braking is another question ? Since european frequecy is 50 Hz one has to wonder how much engineering had to be done to make this change ? Anyone have any information ?
Erikem is admirably suited to answer this in full detail.
It is a bit difficult to extract the sense from what I think is translated German, but it would appear that the setup is heavier because there are separate transformer windings for each of the three powers, presumably stepping down to a standard (unspecified) voltage going to the ‘cubicles’. It woud have been interesting to see a block or circuit diagram showing more precisely how Siemens designed this.
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.
Regenerative frequency ‘synthesis’ is relatively trivial because the frequency ‘standard’ and any waveform distortion can be read directly off the AC line. Power-factor and other corrections would then have to be derived to get correct synchronization. I would expect this to be tracked more or less continuously, and to establish sync within a couple of cycles at most as regenerative power is brought up, so engagement of the brake is essentially ‘instantaneous’ (modulating it up slowly enough to prevent wheelslide taking longer). You would not just slam over from full power to full braking because there will be considerable magnetic energy stored up in the inductive components. However, I would not expect the transition from full power to the initiation of physical regeneration to take very long, and of course the ‘excitation’ to produce effective dynamic braking can then be made as quick as the rail-wheel interface can handle.
The following quotation from RA acceleration schedule seems to be overly optomistic ?
““The ACS-64 offers high efficiency, reduced life cycle cost, and better reliability and availability than Amtrak’s existing electrics. In terms of traction capability with the maximum specified trainload, the ACS-64 can accelerate 18 Amfleet coaches with a Head End Power (HEP) load of 1,000kW to 125 mph in just over eight minutes.””
If someone has a tractive effort curve maybe they can figure out how far the train would have to go to achieve 125 MPH. Do not know what the drawbar pull of 18 caras is to limit the breakaway TE ?. The acceleration of a standard Regional train of 10 cars would of course be less.
I suspect the curve would act as an extrapolation of the one for the AEM7 … very slow initially, then faster in the middle speed ranges, then lower again with HP limitation at higher speed and resistance. I would exoect higher effective low-speed acceleration rate from a modern AC drive, however.
Call the speed 185 ft/s; the average acceleration is then about 21.9 ft/s/m (for the eight minutes) or about 0.38 ft/s/s – well within the ‘comfort’ zone for acceleration. (This is about 1/4 of what I recall was the Metroliner peak acceleration rate of about 1.5 ft/s/s). S (in feet) = 0.5 a t^2, so 0.5 x .38 x 230400 (that’s the eight minutes, expressed in seconds, squared) gives you about 8.29 miles.
Somebody here can probably estimate what an ‘average’ loaded 18-car consist of modern Amtrak equipment is. That will give you a figure to calculate the train resistance, if you must. I doubt a modern AC drive lcomotive will have any problem developing the required “drawbar” TE for any speed below 125 mph, if that’s the question; the AC drive will perform its effective function of traction control essentially just as well via Cardan shaft as it would with truck-mounted motors. And lateral acceleration at the railhead, of course, will be vastly decreased – the French have known this since the early days of monomoteur bogies, and the high-speed testing in the Fifties.
I backed into those performance numbers. Here’s what it looks like:
after 1/2 mile: 65 mph, 1:05
after 1 mile: 80 mph 1:40
after 2 miles 95 mph 2:30
after 4 miles 115 mph 4:50
I assumed the loco weighs 250,000# and has max adhesion of 40%. I used the std Davis equation but adjusted for aerodynamics until I backed into 125 mph in roughly 8 miles. Assumed 93% of traction HP makes it to the rails.
Did piece-wise integration on a spread sheet in 5 mph increments. (I am too stupid or lazy to try calculus anymore!) [D)]
Max acceleration is from 0 to ~30 mph at 1.5 ft/s/s running at adhesion limit, then tapers off as loco perf hits the HP curve and aero drag starts to build.
Piecewise integration is plenty “good enough” for that very benign and smooth acceleration curve. You don’t need the answer to more than one decimal place anyway.
I will proceed to throw a monkey wrench into the above calculations: Since the ACS-64 is a straight electric, have short-term ratings been considered in calculating acceleration rates?[:-^]
So this thing has Cardan shaft drive instead of “nose suspended” traction motors for reduced unsprung mass and less pounding of the track at high speeds.
But isn’t 120+ tons of total weight on what, four axles, a bit much for the kind of speeds contemplated?
What has me scratching my head is this. Amtrak is just going to ask for a whole bunch of money to upgrade the cat (and speeds) on the south end of the NEC. Why not buy a loco that can take advantage of the speed?