EMD AEM-7

The EMD AEM-7 is a twin-cab four-axle B-B 7,000 hp (5.2 MW) electric locomotive manufactured by Electro-Motive Division (EMD) and ASEA between 1978 and 1988. The locomotive is a derivative of the Swedish SJ Rc4 designed for passenger service in the United States. The primary customer was Amtrak, which bought 54 for use on the Northeast Corridor and Keystone Corridor. Two commuter operators, MARC and SEPTA, also purchased locomotives, for a total of 65.

Amtrak ordered the AEM-7 after the failure of the GE E60 locomotive. The first locomotives entered service in 1980 and were an immediate success, ending a decade of uncertainty on the Northeast Corridor. In the late 1990s, Amtrak rebuilt 29 of its locomotives from DC to AC traction. The locomotives continued operating through the arrival of the final Siemens ACS-64 in June 2016. MARC retired its fleet in April 2017 in favor of Siemens Chargers, and SEPTA retired all seven of its AEM-7s in November 2018 in favor of ACS-64s.

Amtrak assumed control of almost all private sector intercity passenger rail service in the United States on May 1, 1971, with a mandate to reverse decades of decline. Amtrak retained approximately 184 of the 440 trains which had run the day before. To operate these trains, Amtrak inherited a fleet of 300 locomotives (electric and diesel) and 1190 passenger cars, most of which dated from the 1940s–1950s.

Operation on the electrified portion of the Northeast Corridor was split between the Budd Metroliner electric multiple units and PRR GG1 locomotives. The latter were over 35 years old and restricted to 85 mph (137 km/h). Amtrak sought a replacement, but no US manufacturer offered an electric passenger locomotive. Importing and adapting a European locomotive would require a three-year lead time. With few other options, Amtrak turned to GE to adapt the E60C freight locomotive for passenger service. GE delivered two models, the E60CP and the E60CH. However, the locomotives proved unsuitable for speeds above 90 mph (145 km/h), leaving Amtrak once again in need of a permanent solution.

Amtrak then examined existing European high-speed designs, and two were imported for trials in 1976–77: the Swedish SJ Rc4 (Amtrak No. X995, SJ No. 1166), and the French SNCF Class CC 21000 (Amtrak No. X996, SNCF No. 21003). Amtrak favored the Swedish design, which became the basis for the AEM-7.

The AEM-7 was far smaller than its predecessors, the PRR GG1 and the GE E60. It measured 51 ft 1+25⁄32 in (15.59 m) long by 10 ft 2 in (3.10 m) wide, and stood 14 ft 9.5 in (4.51 m) tall, a decrease in length of over 20 ft (6.1 m). The AEM-7's weight was half that of the E60CP or the GG1. On its introduction it was the "smallest and lightest high horsepower locomotive in North America." The Budd Company manufactured the carbodies for the initial Amtrak order, while the Austrian firm Simmering-Graz-Pauker built the carbodies for the MARC and SEPTA orders.

Reflecting the varied electrification schemes on the Northeast Corridor the locomotives could operate at three different voltages: 11 kV 25 Hz AC, 12.5 kV 60 Hz AC and 25 kV 60 Hz. A pair of Faiveley DS-11 two-stage pantographs, one at each end of the locomotive, collected power from the overhead catenary wire. Thyristor converters stepped down the high-voltage AC to provide DC power at a much lower voltage to four traction motors, one per axle. As built the AEM-7 was rated at 7,000 hp (5.2 MW), with a starting tractive effort of 51,710 lbf (230 kN) and a continuous tractive effort of 28,100 lbf (125 kN). Its maximum speed was 125 miles per hour (201.2 km/h). A separate static converter supplied 500 kW 480 V head-end power (HEP) for passenger comfort. This was sufficient to supply heating, lighting, and other electrical needs in 8-10 Amfleet cars.

The rebuilt AEM-7ACs used AC traction instead of DC traction. The power modules used water-cooled insulated-gate bipolar transistor (IGBT) technology and provided about 5,000 kilowatts (6,700 horsepower) of traction power plus 1,000 kilowatts (1,300 horsepower) of HEP, twice the HEP capacity of the original DC units. The 6 FXA 5856 traction motors, from Alstom's ONIX family of propulsion components, had a maximum rating of 1,250–1,275 kilowatts (1,676–1,710 horsepower) each and a continuous rating of 1,080 kilowatts (1,450 horsepower). The remanufactured AEM-7ACs were the world's first passenger locomotives to incorporate IGBT technology.