Economical Motor Protection Using Microcomputer Technology

A trend to design new motors closer to their design limits and the high cost of plant shutdown has increased the need for better protection of smaller three-phase motors. A single-chip microcomputer relay can be applied to replace thermal overloads which are of limited effectiveness on low-and medium-voltage machines with comprehensive economical motor protection. The requirement for different protection features and how they are achieved is presented. All the protection features discussed are commercially available in a compact unit that uses a single chip microcomputer.