Class 17E locomotives were modified and reclassified from Class 6E1, Series 7, 8 and 9 locomotives during 1993 and 1994.
Key modifications included improved regenerative braking and wheel-slip control to improve their reliability on the steep gradients and curves of the Natal mainline.
Unlike the unmodified but reclassified Class 16E locomotives, the Class 17Es retained their original unit numbers after reclassification.

A stumbling block was that the regeneration equipment at many of the sub-stations along the route was unreliable.
Since there was no guarantee that another train would be in the same section to absorb the regenerated energy, there was always the risk that line voltage could exceed 4.1 kV which would make either the sub-station or the locomotive trip out.
As a result, the subsequently rebuilt Class 18E locomotives were not equipped with regenerative braking.

Fourteen Series 7 units are known to have been modified and reclassified to Class 17E, their numbers being E1749, E1775, E1776, E1777, E1778, E1801, E1803, E1805, E1810, E1822, E1826, E1827, E1832 and E1843.
Twelve of them were subsequently rebuilt to Class 18E, the exceptions being numbers E1778 and E1803.
Class 17E locomotives were modified and reclassified from Class 6E1, Series 7, 8 and 9 locomotives during 1993 and 1994. Key modifications included improved regenerative braking and wheel-slip control to improve their reliability on the steep gradients and curves of the Natal mainline. Unlike the unmodified but reclassified Class 16E locomotives, the Class 17Es retained their original unit numbers after reclassification.
A stumbling block was that the regeneration equipment at many of the sub-stations along the route was unreliable. Since there was no guarantee that another train would be in the same section to absorb the regenerated energy, there was always the risk that line voltage could exceed 4.1 kV which would make either the sub-station or the locomotive trip out. As a result, the subsequently rebuilt Class 18E locomotives were not equipped with regenerative braking.
Fourteen Series 7 units are known to have been modified and reclassified to Class 17E, their numbers being E1749, E1775, E1776, E1777, E1778, E1801, E1803, E1805, E1810, E1822, E1826, E1827, E1832 and E1843. Twelve of them were subsequently rebuilt to Class 18E, the exceptions being numbers E1778 and E1803.
South African Class 6E1, Series 7