Proposed New Breaker Ratings and Their Efect on Application for Industrial Systems

Simplified breaker application to industrial systems is proposed. Multiplier curves and tables provide the answer. These curves were developed (1) by superimposing calculated induction motor fault currents on synchronous-machine-source fault currents, and (2) by adding "k" factor curves which are an indication of the momentary limits of the breaker. Built-in asymmetrical capability allows breakers to be applied to industrial systems independently of breaker rated interrupting time. One symmetrical-current (E/X) calculation is adequate for breaker application.