ABSTRACT
Automated process plants are controlled by electrical hardware specified on elementary diagrams and designed by electrical engineers. Standard contactors, timing devices, relays, and other provide control functions. This chapter establishes an approach for analyzing and designing elementary diagrams. Electrical hardware used for control includes: relays, timers and time delay relays, push buttons and programmers. Plug-in type relays and prepackaged solid-state components are widely used. The chapter illustrates symbols that are commonly used in electrical control schematics. These symbols are based on the Joint Industrial Council Standards. The chapter also illustrates a typical motor elementary diagram, including the power portion. Logic diagrams use symbols to describe the operation, whereas the elementary diagram uses more words. The logic diagram is an effective tool to convey process requirements, since it is understood by all engineers. Logic diagrams can save design time when used with programmable devices.
