Railroad Trains for the Soul: AC Passenger Diesels
Alternating current traction motors have successfully become more reliable and durable than direct current motors, and AC technology has made a huge impact on motive power in the North American railroad industry. During the 1980’s, various railroads initially experimented with AC traction by converting a few existing diesel locomotives that were originally built with DC motors. The following units were involved in those experiments.
Canadian Pacific 4744 - Montreal Locomotive Works M640 Amtrak 202 - Electro-Motive F40PH EMD 268 - Electro-Motive SDP40F (ex-Amtrak)
Although AC traction is more common on freight locomotives, North America’s very first new diesel-electrics equipped with pre-installed AC motors were a pair of passenger-duty F69PHAC units from General Motors Electro-Motive Division. Numbered 450 and 451, they were tested on Amtrak across the United States and even hauled the German Intercity-Express high-speed train that once visited the U.S. for demonstration tours. However, due to technical problems with the F69 diesels, AC traction became more suitable for heavy mainline freight service in the next few years. In other words, passenger trains generally don’t require high levels of tractive effort that can be performed by the AC motors. EMD debuted a quartet of freight-duty SD60MAC’s by 1992 and they traveled through not only the Burlington Northern Railroad but even other parts of the country. Shortly after testing these experimental units, the BN ordered the EMD SD70MAC, the first commercially successful AC-traction diesel locomotive in North America.
In response, General Electric introduced the AC4400CW for freight service and has even applied AC motors to a passenger locomotive called the P32AC-DM. Also named GENESIS Series II, the P32 is a dual-mode type capable of running on either the diesel engine or the electrical third rail provided in the New York area. The original P40DC (GENESIS Series I or AMD-103) can produce up to 4,000 horsepower and has a top speed of 103 miles per hour. The less powerful P32, however, can unbelievably speed up to 110 mph and can produce higher tractive effort with its 3,200-hp rating, all due to its reliable AC technology. Meanwhile, EMD introduced the DE30AC (diesel only) and DM30AC (dual-mode) locomotives solely for the Long Island Railroad. Since then, other builders have designed AC-traction diesel passenger locomotives primarily for commuter rail systems. Let’s name a few well-known models, some of which were custom-made for a particular client.
Electro-Motive: F69PHAC - Amtrak DE30AC/DM30AC - Long Island Railroad (LIRR) F125 - Metrolink
General Electric: P32AC-DM - Amtrak, Metro-North, and Connecticut Department of Transportation (CDOT)
MotivePower (Wabtec): HSP46 - Massachusetts Bay Transportation Authority (MBTA) MP54AC (or MP40PHT-T4AC) - GO Transit
Alstom: PL42AC - New Jersey Transit
Siemens Charger Series (currently in production): SC-44 SCB-40 ALC-42
For traction, some AC passenger locomotives, particularly the EMD F69PHAC and DE30AC/DM30AC, have an inverter-per-truck configuration; others have individual axle control where each inverter controls only one traction motor. When it comes to head-end power, virtually all AC passenger diesels feature at least one additional inverter to provide electricity for the passenger cars. By the time the Tier 4 emissions regulations went into effect, all of the newest diesel-powered passenger locomotives have AC traction as the standard feature.
Although the experimental F69PHAC’s did work in some of Amtrak’s long-distance services, the new Siemens ALC-42 Chargers will be the first production AC diesels to haul people across the U.S. While the GE P32’s on the other hand do have the AC technology, they are more intended for Amtrak’s corridor operations within the state of New York. Interestingly, these locomotives have carried the long-distance Lake Shore Limited but only from New York City to Albany (and vice versa), so the more ubiquitous P42DC would be assigned to carry the same train for the rest of its way to Chicago. Despite their teething troubles, the F69PHAC twins can be described as the prelude to the entire AC-traction era in the history of North American diesel-electric locomotives. Today, this technology has proven to be more effective for hauling not only freight but even passengers in both intercity and commuter rail operations.
Sources:
Locomotive 2020 | Trains Magazine
Photo credit: Mark Wurst
