Join the discussion on the following article:
EMD axle control technology hits the road
Oh dear, it should mean:
This causes that the axle load of the first axle in the bogie decreases and the axle load of the last axle increases.
Have inadvertently interchanged it…
If there is only one converter per bogie all 3 tracion motors could only be controlled to an identical torque.
But there is the problem that always - also in modern truck designs with as deep as possible arranged drawbars between bogie and the locomotive frame - this force transmission always happens above the force transmission between wheel and rail.
This causes that the axle load of the first axle in the bogie increases and the axle load of the last axle decreases.
And if there is only one converter per truck all 3 axles could only transmit the drag force the axle with the lowest axle load can.
If every traction motor has ist own converter, every single one can be controlled to its individual maximal posible power.
Another advantage of an inverter (converter) for each axle is that wheel size differences matter less.
Consider that entering a curve the lead axle’s wheels take the brunt of the steering effort and then get ground down more than trailing axles, many miles later the wheels might differ by a half inch— or more. Less sophisticated Wheel Slip control circuitry compared axle speed and regulated load to reflect the likelihood that the fastest wheels needed correction but reduced the out put of power to all axles to account for the fastest wheel set…and the different wheel sizes contributed to speedometer inaccuracies; one axle informed most speedometers of the a measurement that was converted into a display of speed…Bigger wheel less speed smaller wheel faster.
This exemplary morning in Tracy, Ca. I’m called for an Oakland bound…
One unit…7,800 tons…the ICC shows up and finds the wheel size differential a violation.
Went back to the hotel—
I believe one consideration was that the failure of one inverter in the original design would kill the entire truck resulting in a 50% reduction in pulling power. The GE design looses only one axle when its related inverter fails. I think this would also be the case with the new EMD. Carstens comments could be the reason that EMD went with the B1-1B wheel arrangement on its new six axle engine with 4 traction motors.
It would have been nice to hear some details on the reason for the increase in the number of inverters. Each one produces less heat? The cost of the smaller inverters is less than the larger ones? They are controlled individually for greater tractive power? What?
UP’s test car number 210 looks like a uniquely modified passenger car. I think I even see a Goosie sticking his head out the window!!
What is the second vehicle in the consist? Is it the ex- S.P. Krauss-Maffei track geometry/video car/loco? Certainly appears to be one, the three windows on the left hand side of the vehicle make it looks very much like one, however I can not expand the photo enough so that I can confirm. Can anyone advise?
The core of a locomotive inverter is a bank of Gated Turn-On devices (GTOs). The original AC traction locos (GE AC4400CW and the SD70MAC) had different concepts. The GE had six inverters, each having a bank of GTOs sufficient for 1/6 of the load. EMD chose to use just two inverters with three times as much GTO capacity. At the time, it was felt by GM that there was no reason to individually control the axles.
Time has proven that individual axle control is superior for many reasons. If one axle suddenly accelerates, the controlling computer recognizes that it is slipping and reduces the speed of the axle until it hooks up again. The differential of wheel diameter is also dealt with as are several other technical issues. This would include trucks with unpowered axles (A-1-A or 1-B B-1 arrangements).
The one question that’s been on my mind for a while now is that with the new axle control technology and inverter per truck will this actually increase the tractive effort on these new units? If I understand correctly the new units also has a new software. Is this true?
The one question that’s been on my mind for a while now is that with the new axle control technology and inverter per truck will this actually increase the tractive effort on these new units? If I understand correctly the new units also has a new software. Is this true?
@GREGORY MCCULLOCH - Article says it’s Union Pacific test car No. 210, supposedly it’s famous enough to warrant a HO scale model being available: http://www.brasstrains.com/classic/product/detail/032500/ho-omi-1337-up-union-pacific-d
Thanks a heap for all the informative comments! There is an amazing body of knowledge available in Trains readers. Thanks again.
Goosie in a passenger car? C
'mon, Vasyl; Goosie would’nt be caught dead in a passenger car!
@LEON JOHNSON - Not directly. The same amount of power in total will still be delivered to the motors, this time split across more motors. But as others point out, this allows more control so issues like wheel slip - which is both damaging to the infrastructure and also a complete waste of energy - will become less of an issue. It could result in overall efficiency improving.
Thank you Paul Harrison for your answer. My next question is would the new axle control technology require a totally new software for this operation?
Nice to see EMD still behind the curve.Amazing.
Well! EMD locos manufactured in India under license had changed over to one inverter per axle about 5-6 years back.
They also are rated at 4,500 HP after indigenous software modification at around the same time.
EMD had tried B1-1B configuration on passenger version of SD70MAC and it was a flop. Indian Railway switched over to C0-C0 configuration with modified software and it works great.
WHAT … is/does the inverter do?.???
An inverter converts DC to AC. An AC motor is fed current that alternates polarity between its two wires. Think of flipping a battery rapidly back and forth between the +/- terminals. The frequency of the Alternating Current determines the speed of the motor (generally). If you have a ceiling fan in your house, that’s an AC motor, but since the electricity in your house is already alternating, there’s no inverter involved. An AC diesel locomotive makes its own DC from the diesel engine/alternator/rectifier and inverts it to AC for the traction motors in the locomotive’s trucks. EMD used one inverter (so one frequency and one speed) per 3 axles; now it’s trying one inverter per axle (so each axle’s speed can be individually controlled).