Q. Digital controller for a steam-turbine driven generator?

Figure illustrates the basic elements of a minicomputer system in terms of a block diagram for speed and voltage control (as well as data acquisition) of a turbine-generator unit. Typical output variables of the generator are speed, rotor angle, terminal voltage, field (excitation) current, armature current, and real and reactive power. Some output variables are measured by digital transducers, whose outputs are then digitally multiplexed and sent back to the minicomputer.

Some other output variablesmay bemeasured by analog transducers,whose outputs are processed through an analogmultiplexer which performs a time-divisionmultiplexing operation. The output of the analog multiplexer is connected to a sample-and-hold device, which samples the output of the multiplexer at a fixed time interval and then holds the signal level at its output until the A/D converter performs the analog-to-digital conversion. Thus, following the multiplexer, time sharing is done amid a number of signal channels.