SJ Mg

Mg
SJ Mg 620
Type and origin Power type Electric Builder ASEA Build date 1944-1945 Total produced 17
Specifications Configuration: ​  • UIC Co′Co′ Gauge 1,435 mm (4 ft 8+1⁄2 in) Wheel diameter 1,000 mm (39.37 in) Length 16,800 mm (55 ft 1+3⁄8 in) Height 4,500 mm (14 ft 9+1⁄8 in) Loco weight 102 tonnes (100 long tons; 112 short tons) Electric system/s 15 kV  16.7 Hz AC Catenary Current pickup(s) Pantograph
Performance figures Maximum speed 80 km/h (50 mph) Power output 2,640 kW (3,540 hp) Tractive effort 300 kN (67,000 lbf)
Career Operators Statens Järnvägar

Mg is an electric locomotive used by Swedish State Railways (Swedish: Statens Järnvägar, SJ) for hauling freight trains. It was built in 17 copies by ASEA and was in service until 1980.

The Mg-series was built for the electrification of Norra Stambanan in the 1940s. It was steeper and more curved than the main lines in Southern Sweden, and single-track sections meant that long freight trains had to be used to make best use of line capacity. The D-series was not powerful enough and the Of-series was too long for the curves. But as experience of the building of bogie-locomotives increased, a Co'Co'-design was chosen for Mg, as the first bogie-locomotive in Sweden.^[1] More power also meant that the direct current motors from the D-series had to be replaced with the alternating current motors of the F-series. The machine room was not symmetric, so the loco was not the same on the right and left side. The Mg was the basis for the Ma-series built in the 1950s.

• Tore, Nordin; Wretman, Lennart; Grundstedt, Ove (1998). Svenska Ellok [Swedish Electric Locomotives] (in Swedish). Stockholm: Svenska Järnvägsklubben. ISBN 91-85098-84-1.

• Järnväg.net on Mg (in Swedish)