Therefore, a locomotive with AC traction can provide the same tractive effort as a DC locomotive weighing twice as much or can give twice as much tractive effort for the same weight.
This can enable less powerful locomotives, or a. More modern DC systems incorporate a wheel slip control which senses the beginning of a slip and automatically modulates the power in order to retain control.
The AC system, however, operates in a very different fashion. Considering the Monthly Avg. Posted by Anonymous on Wednesday, September 21, creative writing workshops buffalo ny For all you engineers, is AC easier to operate in a locomotive, or DC, or no diff??
Again, the adhesion levels are much higher so the locomotive can again be significantly lighter for the same amount of braking.
As well, no brake shoes have been replaced so far, as predicted. The other major difference is that the switched coils on the DC motor are on the rotor or the moving part while the switched coils on the AC motor are on the outside.
Therefore, at full power, as the speed drops the traction force goes up until either the motors overheat or the wheels spin. AC motors use sensors to detect the rotation of the rotor and electronic switching to accomplish the same trick of keeping the magnetic field ahead of the motor.
This is why the AC locomotives can run at slow speeds with higher traction forces for a longer period of time than the DC locomotives. Overall, the only disadvantage of the AC is the added cost of the high power electronics required for the electronic commutation.
Traction force is directly proportional to the current running thru the motor and, unfortunately, so is resistance heating. The locomotive adhesion variable represents the ability of the locomotive to convert the available friction into usable friction at the wheel rail interface.
The AC locomotive, however, can control to a specific motor torque level allowing the tractive effort to be essentially constant at the higher range of available adhesion.
All in all, the AC traction locomotive offers about twice the amount of adhesion as a DC unit. Until the mid s this was only practical with the brush-type DC motor, although such DC can be supplied from an AC. As the traction motor cooling is more effective on the AC motors, the AC locomotives can produce more low speed traction force for a longer period of time without overheating the motors.
With AC traction, however, the braking can be much higher because the drive system in braking acts just like the drive does in traction thus eliminating wheel slip. While it has been used in locomotives for over two decades especially in Europeit has only been recently that the price of the drives has allowed them to be used in most of the new diesel-electric locomotives in the United States.
Power is speed multiplied by force. As the wheel slippage increases, the coefficient of friction also drops rapidly to a level of 0. Therefore, when using standard friction braking tread brakes the braking capability of the locomotive excluding train braking is proportional to the locomotive weight.
Next, the DC locomotive typically has a number of throttle settings with a set power level for each one. Attopounds these units are typically rated at about 40, pounds tractive effort continuous somewhat higher intermittent but limited by traction motors and generators.
As the motor turns the magnetic field has to stay ahead so it always trying to pull the motor around. DC motors were used to run machinery, Essay foreshadowing act romeo juliet and scene often eliminating the need for a local steam. The AC produced is not really the same as household AC as the frequency is dependent on the speed of the diesel engine.
It varies dramatically from about. While this sytem is simple and effective, it does not produce a constant motor torque since power is the product of torque and speed.
The tractive effort of a locomotive whether AC or DC is defined by the equations: The dynamic braking in AC traction locomotives also allows full braking down to zero speed, unlike DC dynamic braking. The following table has been generated considering the diesel items in the fuel vendor invoices received in the timeframe defined.
Thus, the newer locomotives have about twice the adhesion of the older units and the Class I railroads are, in fact, typically replacing two older units with a single new AC unit.
So what went wrong? As with traction, braking is a function of weight on drivers.This report presents a comprehensive comparison of AC traction vs.
DC traction for locomotives, reviewing the advantages such as greater adhesion levels, higher reliability, and reduced maintenance requirements. Apart from an analysis of the equations used to determine tractive effort and adhesion of an AC or DC locomotive, the paper also. AC vs. DC traction.
Posted by Anonymous on Wednesday, September 21, PM Can someone explain to me what are the pros and cons of each of the traction systems, and for what kind of jobs would it be preferable to use one over the other? AC locomotive's greatest advantage is in low speed drag service, pusher service, mountain.
The only difference in the way A.C. and D.C. run is that a train powered with A.C. locomotives can have a very low horsepower-per-ton ratio and still move without exceeding the heating limits on the traction.
AC Traction vs DC Traction; Old vs New; Performance Audit; About Us; Contact Us; Republic Locomotive Performance Audit. The following is an internal audit prepared by one of our customers: Introduction. During we purchased 3 new technology locomotives from the manufacturer, Republic Locomotive.
In the report included in the note “Vendor. In addition to the list of locomotives and comments in the previous post, keep in mind that on AC traction locomotives, there is an alternator, but the power is first converted from AC to DC and then inverted back to AC.
A Comparison of AC Traction and DC Traction in Locomotives PAGES 2. WORDS View Full Essay. More essays like this: ac traction locomotives, dc traction locomotives, diesel locomotives. Not sure what I'd do without @Kibin - Alfredo Alvarez, student @ Miami University.
ac traction locomotives, dc traction locomotives, diesel locomotives.Download