SJ Mg

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.

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

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. 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.