History
In 1992,
Electro-Motive demonstrated its first heavy haul freight locomotives for
revenue service in North America. These locomotives incorporated
three-phase AC traction system technology initially developed by Siemens
A.G. for the European rail market. Siemens and EMD, after forging a partnership in
technology, worked together extensively over several years to adapt this system to
fit the demands of the North American rail market. This development included the
construction of a total of seven prototype AC locomotives.
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Union Pacific demonstrators meet CP
5932, location unknown - Greg Sherwood.
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In 1987, the partners tested EMD 268, their first AC traction freight locomotive. The
fundamental traction system deign of this unit was significantly different from that
used on all other AC units built by EMD since. Though never used in revenue service,
EMD 268 provided valuable foresight to many hurdles that were to come along the path
of development. EMD 268 had rigid non-steerable HTC trucks and a SIBAS
locomotive Control Computer from Siemens, unlike the production SD70MAC, SD80MAC, and
SD90MAC units with the HTCR and HTCR-II radial trucks and EM 2000
Locomotive Control Computer. These components combined with the EM 2000 control
system make up the RADIALAC system developed by the partners. This
all encompassing system is the key to the success of the EMD production AC
locomotives.
During 1989, EMD built two F69PH-AC passenger units for Amtrak (road
numbers 450 and 451). These units used Siemens AC technology for the traction system
and also for the Head End Power generation system. These units were tested extensively
first at the United States Department of Transportation Test Center in Pueblo,
Colorado then later through 1992 in revenue service on Amtrak across the United
States. Though limited in their success early on, again the project served to educate
the partners in "real world" circumstances, and provide a hint of what lay
ahead on the road of development. Later revision and further demonstration secured the
first passenger AC traction order for EMD with the Long Island Railroad in 1995.
The market had yet to witness the potential of AC traction systems in the heavy haul
freight market. Still to come were the SD60MAC prototype locomotives with essentially
the same traction and control systems. Many observers expressed skepticism in light of
the early F69PH-AC performance, but they failed to realize the real
advantage of AC traction systems at low speeds under heavy loads, an advantage that
would soon shine through and silence all critics. The potential for adhesion levels
higher than had ever been seen before under even the most adverse conditions
propelled the partnership forward into its next development stage.
During 1991, EMD began construction of four SD60MAC prototype locomotives. The units
were to contain a 710G3B diesel rated at 4,000 tractive horsepower as the prime mover.
While other units were under construction, the first of the MAC's (as they would soon
become known) began testing at the Transportation Test Center in Pueblo, during
January of 1992. Testing at the TTC continued through the summer, eventually with a
second unit, until July when a consist of 3 units was assembled, tested, and ready
for service in a testing/revenue capacity on Burlington Northern Railroad. The
original target for continuous tractive effort ratings on these units was 117,000
pounds. However, after extensive testing and revisions to control software at the
Test Center, the real potential of the system was realized as the rating increased to
125,000 pounds and finally to 137,500 pounds.
Once testing at the TTC was complete, BN tested the units in revenue coal service out
of the Powder River Basin and confirmed all claims that had been made in terms of
rail and flange wear reduction with the new radial truck as well as tractive effort
with the RADIALAC system during testing at the TTC.
A rather dramatic example of the potential of the units took place in October of 1992.
A revenue coal train of 15,000 tons was to be pulled on a grade with several curves,
south of Pueblo. Normally, 5 SD40-2's, each developing 19.5 percent
adhesion, are used to make this run. Computer simulation had predicted that nearly
380,000 pounds of tractive effort (32.5 percent adhesion per unit) would be needed to
run such a train through the corridor. This prediction was verified during a test run
in August 1992. During the October test, though, the train was intentionally stopped
on the hill to determine if three SD60MACs alone could start the train. To start such
a train, 5 SD40-2 units would need to generate 27 percent adhesion each,
while 3 SD60MACs would need to generate an average of 45 percent adhesion each. With
the 116 car train stretched, the MACs pulled away smoothly by generating full starting
tractive effort (175,000 lbs. per unit) accelerating up to 12 miles per hour (only
2-3 MPH slower than a consist of 5 SD40-2s).
Generation of the 27 percent tractive effort per unit required for a consist of 5
six-axle units is well within the limits of newer DC locomotives, but
extreme concern over damage to the commutators would come into play, and normally
forbid such operation under normal circumstances. With the induction motors used in
the RADIALAC system, though, EMD-built locomotives
can be operated at a full throttle/full load condition at complete standstill without
such concerns.
Demonstrations such as these were repeated time and time again over several months
with coal and other types of trains in all weather conditions. As an end result, it
was determined by EMD, Siemens, and BN that the SD60MAC units would replace the
SD40-2 locomotive by a ratio of 3 to 5. That is, 3 MACs at 4,000
tractive horsepower each would replace 5 SD40-2 units at 3,000
horsepower each. This conclusion resulted in the largest single investment in
locomotives in history. Burlington Northern ordered 350 SD70MAC units to be delivered
between 1993 and 1996. But before the SD70MAC could be built, more major testing
needed to be done.
During the latter part of 1992 and early part of 1993, EMD built three prototype
SD70M demonstrator units. These DC locomotives were built to test and evaluate the
new EM 2000 microprocessor locomotive control system. The control system had already
gone through several development stages in application on an EMD lease Fleet unit.
Eventually, the demonstrator units would travel the country to exhibit the
enhancements of the new control system, the flexibility of the Integrated Cab
Electronics system from Rockwell International, the increased adhesion and ride
qualities afforded by the HTCR radial truck, and the noise reduction and comfort
provided by the modified console control stand style cab or "M Cab design",
electronic air brakes, four cylinder air compressor, a modified engine, 42 inch
diameter wheelsets, and many other features. These units, as many before them, were
tested extensively at the Transportation Test Center. With a paint scheme that parted
from the usual blue/white of General Motors, the units began their tour in March of
1993 and impressed many from all walks of the rail industry not only with performance
but also appearance. Shortly after these units began their tour, six prototype SD70s
(DC traction locomotives) with standard cabs were delivered to Norfolk Southern. Based
upon performance of these units, NS soon ordered 50 more of the locomotives on a
production basis. This provided a real proving ground for the new EM 2000 control
system as well as the 710G3B engine and radial truck, fundamental components of the
RADIALAC system.
Finally, in December of 1993, EMD delivered the first of a new breed to Burlington
Northern. The SD70MAC incorporated all of the latest in technological advances by
pulling together the systems that had been refined on the SD60MAC and the SD70
prototype units. This meant that the locomotive incorporated the same fundamental
three phase AC traction system as implemented on the SD60MAC units, but used the EM
2000 microprocessor locomotive Control Computer that had been developed on the DC
traction units in place of the SIBAS 16 "master" from Siemens.
©
2005 William C. Slim
http://www.okthepk.ca
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