The D, introduced in 1925, was the first standard electric locomotive of the SJ that was built in greater numbers. It had the wheel arrangement 1-C-1 and two traction motors which worked on a common crank axle and coupling rods. In the first batches, each traction motor had 610 kW and the locomotive body was made of wood with gangways on the fronts. The freight variant with a gear ratio for 75 km/h was designated Dg, while the passenger variant with a gear ratio for 100 km/h was designated Ds.

After 134 locomotives built, construction of the body switched to steel in 1933. From this point on, the original locomotives were called D (I) and the new ones D (II). Later, when repairs were made on the D (I), the cabs and other parts were rebuilt with steel. Starting in 1936, new traction motors with 735 kW each were installed. When production was completed in 1943, 333 had been built. These included nine built for the Bergslagernas Järnvägar (BJ) and three for the Dalslands Järnväg (DJ), which later came to the SJ.

In the fifties after the introduction of the Da, the D locomotives got the same 920 kW motors. Now they were even powerful enough for freight trains with the 100 km/h gear ratio, what made the distinction between freight and passenger variants superfluous. So they were now called Du, with the “u” standing for “universal”. Between 1967 and 1976, 162 were rebuilt to the Du2 by the removal of the gangway doors and installation of the connectors for multiple controls in the same place. Now they were used double-headed to achieve the same power as two of the new Rc. The first withdrawals had already started in 1967 and all were gone by 1988.