"The MAC's are arriving"; and, they might be powering the next train you are called for. Now appearing in larger numbers on the Union Pacific are the latest version of alternating current locomotives from General Motors, and they are seeing action on a variety of train types.
As these units are outfitted with equipment new to operating and mechanical personnel (one of these items may well be a first for locomotives), a fellow employee and a fine gentleman thought it would be a terrific idea to do a feature on this new locomotive. Well, for those of you who have come to know this writer are aware, if it's newsworthy, I'll give it my best and go for it.
So for this month's edition, the star of the show will be the SD90/43AC locomotive.
Before We Begin
For the purpose of this article (along with helping facilitate a transition), many of us have referred to this unit as the SD90MAC. However, do keep in mind the following for the transition to how the UP will "officially" designate these units.
The 4300 horsepower versions will be called SD90/43AC's, while the upcoming 6000 horsepower models will be called the SD90AC. These designations are being used because, when it gets down to it, the two are, of course, different versions of locomotives. So in order to avoid confusion (which we at this publication strive to accomplish), please make note of these changes. Now we return to the program already in progress.
The SD90/43AC Locomotive
The current version now operating on the UP is called the SD90/43AC: it is a "convertible" locomotive which is outfitted with traction motors, electrical control systems, and mechanical systems designed for operation with the forthcoming 6000 horsepower diesel engine (more about this will be in a later outline).
In the meantime, the model of diesel engine installed is rated at 4300 tractive horsepower, hence the reason for the 43 in the designation.
The large overhang at the rear is for the radiator system; this locomotive utilizes a feature called the split cooling system, an item required for the upcoming 6000 horsepower engine (this is also an added plus for any type of engine application).
They can produce up to 185,000 pounds of tractive effort, and up to 96,000 pounds of dynamic braking effort. The EPIC brake system is in use, along with the integrated display screens and desktop controllers.
Cab air conditioning along with regular fans are also in place. All of this is contained into a feature called the isolated cab; it made its first appearance on Conrail SD60MI model locomotives, and now this feature has made its way onto locomotive orders of the UP ( as well as other major carriers).
The units sport the radial trucks, which provide both a smoother overall ride along with reduced wheel wear.
The dynamic brake grids have been repositioned to the very rear of the locomotive; this aids in reducing the levels of noise around the cab.
There are some other major differences in which operating crews will note as well; the most noticeable to operating crews will be the electronic fuel injection system, the parking brake appliance, and the feature which has generated the most comments from personnel, the Rollback-Opposite Direction Braking capability (which I came to know under the term of enhanced rollback). Let's take a closer look at these three items.
The EMDEC System
The electronic fuel injection system is called EMDEC; this stands for Electro Motive Diesel Engine Control. This system does not use the traditional layshaft or governor appliances; instead, it uses electronic controllers and sensors for conducting proper operation of the electronic fuel injectors.
EMDEC also makes use of larger piping for the fuel system. It has its own annunciator panel which will describe what caused an engine shutdown.
A key item to note about this locomotive is that the engine starting switch has been moved from the engine room to the control panel inside the locomotive cab.
The starting procedure itself is different from what we have been accustomed to over the course of operating locomotives; once the engine start button has been pressed for two to three seconds; the engine priming along with the engine starting sequence will be handled automatically.
Before the unit actually starts, you will hear an engine start alarm to inform you of the impending event. Be sure to monitor the display screens on the locomotive control stand, as they will give you status messages on what event is taking place.
Should the engine start not be successful, a message will be displayed indication what condition was discovered which led to aborting the attempt.
A better understanding of this may be obtained from the operators manual now being distributed to locomotive engineers; should you not have a copy, consult your MOP.
The Parking Brake System
We all know about the parking brake which is used on automobiles, but did you ever think such an item would make an appearance on a locomotive? Well, in the world of modern advancements, not a whole lot of ideas are considered far-fetched anymore, so why not give it a try?
These locomotives feature as one of its appliances the electric parking brake; it is a remotely operated device which has its operating controls located in the locomotive cab.
It uses an all sealed DC motor (the only DC operated motor any place on the locomotive) to operate the other equipment involved. Next to the controls is the parking brake meter, which will identify when the system is in full application or full release.
The current format requires approximately 45 seconds for either process to happen; once it does, the needle will then shift into the affected zone, depending upon if you are applying or releasing the brake.
If in a turnover to you, they have indicated the system is in the applied position, be very certain to obtain the fully released reading on the meter before moving the locomotive (there have been some cases of these units sustaining flat spots because of this).
The parking brake system may also be operated manually; a hand crank on the left side of the No. 1 truck is provided for this.
A highly important message about the manual operation: NEVER perform this method whenever there is power being supplied to the system. When the equipment is functioning properly, the manual operating method is NOT to be performed.
Another important item a fellow employee asked me to pass along to you: prior to using the electric parking brake, if anyone is near the No. 1 truck, ascertain if they are in the clear before you begin the procedure.
Along with reviewing the chapter on the parking brake system in the operating manual, there is available a videotape as reference material.
Enhanced Rollback:
What it is and What it Does
As a longtime follower of the latest in locomotive technology, I have come into knowing a lot about some of the more intricate workings in how locomotive control systems "co-operate" with one another to produce the effects they do when certain operating conditions present themselves.
During some of the cab design committee's trips to the GM facility in La Grange, Illinois back in 1994 was when I first heard about a feature which now I have received the largest comments about; the term I came to know this under was enhanced rollback, but to break it down into their more specific relations, they are called the phases of Rollback and Opposite Direction Braking (ODB).
These are in place to assist you in getting under control the locomotive operation should track speed, while moving in a direction opposite of the reverser, happens to take place.
It is there as a safety feature; under no circumstances should this be done with operating locomotives, particularly since the air brake rules and other guidelines for correctly starting trains are to be adhered to. Enhanced rollback came into being as a result of improved understanding of how alternating current flow is conducted whenever the locomotive is operating in dynamic braking (No, I won't explain that here, but feel free to ask me if you are interested).
Once this knowledge was obtained, it was then determined how to transform those qualities into what is called enhanced rollback. The feature requires special versions of computer software for both the EM2000 locomotive control computer and the Siemens SIBAS16 inverter control computers (if one is installed without the other, the result will be a no load output from the locomotive due to the "mixed bag of signals" due to the non compatible software parts).
The control system detects traction motor rotation with the aid of two speed sensors in the traction motors; the magnetic portion of the motor is picked up by one of these sensors, and then that sensor will detect the direction of the motor.
Once the speed which is need for activation of the dynamic brake system for the ODB part of this feature, the activation process will begin with the inverter computers, which will then send a signal to the EM2000. EM2000 has the program which will bring on line the dynamic braking system.
As outlined earlier, there are two phases in enhanced rollback; they are Rollback and ODB. In the Rollback phase, the locomotive can go up to its maximum tractive output of 186.000 pounds, and will attempt to load up in power throttle as long as track speed does not exceed 4.5 MPH.
But if the 4.5 MPH threshold is exceed, the unit will then switch over to Opposite Direction Braking. In ODB the locomotive will produce it maximum dynamic braking output of 96,000 pounds.
When in ODB, the feature is not speed dependent on the top end, nor is it throttle handle dependent; it will stay there until track speed reaches 2.5. MPH, at which time, the locomotive will then go back into the Rollback mode, with a gradual return of output back to the throttle handle position.
If the throttle is in idle, and the locomotive begins to roll opposite the direction of the reverser with track speed between 0.1 MPH and 12 MPH, the unit will go into ODB. However, if the speed is above 12 MPH and the reverser position is changed to the direction opposite of locomotive travel, then no ODB will be engaged.
A final note about the enhanced rollback feature: it does require that at least one inverter be cut-in for it to be available to operate.
Cutout Inverter Notes
Although it may not be that likely, you may encounter one of these type locomotives with an inverter in a cutout state (it may have been done automatically or by the manual cutout program in the EM2000 computer).
So with the inverter per truck arrangement in use on these locomotives, how does this affect their performance? Whenever you have this condition in effect, if you are operating in No. 8 throttle, you will have available 60% of the locomotive's maximum rated tractive effort.
In the other throttle positions, starting at No. 1 throttle, you will begin at 78% of full power, and then progressively work down from that amount as you work your way up to No. 8 throttle, where at that point, it will not be less than the 60% figure.
As a means of aiding the set of trucks with the cutout inverter, the inverter to the remaining truck set will increase its output.
Now , let's take a look at this same condition, only now you are going to use the dynamic brake. Unlike DC model locomotives, if a traction motor (in this case, the inverter) is cutout on this locomotive, it will retain dynamic braking operation; the figure will also be 60% of its full capability.
It is able to do this because on an AC unit, the traction motors are not directly connected to the dynamic brake grids (they are connected to the DC Link switchgear). The inverters, when dynamic braking is in use, convert the traction motors AC output into DC, then apply that current to the DC Link.
So the DC Link is merely receiving a lesser amount of DC contribution, but nevertheless, what is being applied to it is then routed to the grids.
SD90/43AC Units 8025-8074:
A Special Notes
On this order of locomotives, you will note their having a larger number of switches and circuit breakers on the engine control panels.
A number of them will have across their ID labels a symbol which became famous by the movie Ghostbusters; these particular switches are not operational on the UP locomotives and should be disregarded (a modification is being worked on by which these controls will be locked down to prevent such occurrences).
Since our locomotives, along with the Conrail SD80MAC units are constructed on identical platforms, it was decided by the manufacturer to come out with what is called a universal cabinet, which would facilitate manufacture of either version of locomotive (the SD80MAC has a 20 cylinder engine rated for 5000 tractive horsepower).
So again, if one of these controls has a Ghostbusters ID on its label, it is to be disregarded, since it is non operational.
A Look Ahead
The latest developments in the saga of the upcoming 6000 horsepower SD90AC will be the focus of next month' s column. I will also report on developments with the testing of the Integrated Distributed Power control system, along with some interesting action to have happened in Texas with some of the SD90/43AC's, which included a couple of conventional coal trains which were powered by a trio of these new units.
And Now, A Message From Our Sponsor...
I was asked to pass along the note to train and engine crews that we need to be conscious of and comply with observance of locomotive short time ratings.
This is an area of operations which is important to preventing damage to the traction motors and other associated components. In next month's issue, I will have a special feature which will in more detail address what this is and how to be governed accordingly. It will also go into how this protection is accomplished on all types of locomotives.
Meantime, take a moment to review the guidelines for handling trains whenever you may possibly face having to perform portions of your trip under this situation.
Thank you for your attention.
Marcel is a locomotive engineer working the Fort Worth to McAlester Freight Pool.
10-18-96