Date of Award


Document Type

Open Access

Degree Name

Bachelor of Science


Electrical Engineering

First Advisor

James Hedrick


Circuit Breaker, Automated System, Power Supply, TRIAC, Underwriters Laboratory, Trip Performance


Norbrun, Marlie Circuit Breaker Failure Analysis System. Electrical, Computer, and Biomedical Engineering Department, June 2021.

ADVISOR: Professor James Hedrick

Electrical malfunctions are one of the leading causes of domestic fires in the United States. Between 2012 and 2016, electrical failures were responsible for 44, 860 residential fires (Richard Campbell, “Home Electrical Fires”). All electrical circuits contain circuit breakers, which are used as safety mechanisms to interrupt current flow when a fault develops. It is not always possible to determine if an electrical fire resulted from a circuit breaker malfunction. Thus, it would be beneficial to have a cost-effective and user-friendly system that allows people to test the circuit breakers in their homes regardless of their technical background. The purpose of this capstone project is to develop a reliable and cost-effective automated system capable of testing multiple residential circuit breakers to determine their trip response in the event of a circuit fault.

The automated system adopts the UL 489 test procedure from the Underwriters Laboratories (UL) to test the circuit breakers. The system contains a computer-controlled power supply that outputs a variable current which generates enough heat to trigger the circuit breaker under test. Moreover, the system uses a solid-state bidirectional current controller known as a TRIAC to regulate the current delivered to the circuit breaker being tested. Overall, the automated system can be used to test new and currently installed circuit breakers to determine whether they are capable of preventing electrical fires.