The 27 Class 150 3000V DC Bo-Bo electrics were introduced in 1978 as a DC only version of the dual system Class 350 for express passenger work.
Half the class were upgraded for 160km/h running, becoming Class 151. The remaining Class 150s were later upgraded to 140km/h maximum speed.
The 120km/h maximum speed became problematic as lines were improved and 13 were subsequently upgraded for 160km/h running, becoming Class 151. The remaining 14 were later upgraded for 140km/h running and renumbered into the 150.2xx series.