A drive unit for housing components of a drive system for an electrical machine, such as an electric motor, comprises a cabinet having opposed first and second relatively narrow faces and a wide face between them. An interface for inputting and deriving data is mounted on a bracket to the unit and faces in the same direction as the wide face. The unit can be installed conveniently in situations in which depth is limited, while at the same time enabling the drive unit to be programmed and set in a convenient way.