Circuit Breaker Basics

This 2 hour session will review how the circuit breaker operates and how it is used in power distribution systems. The discussion will cover construction of the circuit breaker from thermal magnetic devices to those with electronic trip units. The student will understand what the labels and markings are on these circuit breakers. Applying circuit breakers involves understanding their ratings and ther time-current characteristic (TCC) curves. Some key areas of exploration will include the following: 1. Labeling / marking 2. 80% rated vs. 100% Rated 3. Ratings (Interrupting, voltage, current) 4. The TCC Curve 5. Arc Reduction Maintenenace Switch 6. Zone Selective Interlocking 7. Communications 8. GFCI / GFPE / AFCI Here are some references: Selecting Protective Devices (SPD) http://www.cooperindustries.com/content/dam/public/bussmann/Electrical/Resources/technical-literature/bus-ele-br-3002-spd-2017.pdf NEMA AB-4 https://www.nema.org/Standards/Pages/Guidelines-for-Inspection-and-Preventive-Maintenance-of-Molded-Case-Circuit-Breakers-Used-in-Commercial-and-Industrial.aspx UL Marking Guide for Circuit Breakers: https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=2ahUKEwj37PXfs9voAhXakHIEHT2zDjYQFjAAegQIARAB&url=https%3A%2F%2Fcode-authorities.ul.com%2Fwp-content%2Fuploads%2F2014%2F09%2FCircuitBreaker_MG.pdf&usg=AOvVaw0YrFdmZqaO7x2ZAWK6AsBm Eaton MCCBs https://www.eaton.com/us/en-us/products/electrical-circuit-protection/circuit-breakers/molded-case-circuit-breakers.html All Eaton Circuit Breakers https://www.eaton.com/us/en-us/products/electrical-circuit-protection/circuit-breakers.html