EWRB theory prep – MCBs Exam
Questions with Complete Solutions
describe (A. trip operating unit ) component function - ANSWER bi-metal/mag. provides
mechanism for detection of fault current and opens contacts
describe (B. control contacts unit ) component function - ANSWER contacts allows the
supply current to flow during normal running when MCB is closed
describe (C. arcing ext. unit ) component function - ANSWER all inclusive factors -
horns, chamber chutes, oils, splitter plates, used to control and extinguish fault arc
describe (D. frame unit ) component function - ANSWER molded case exterior provides
a rigid, mechanically strong, insulated housing for MCB parts
Low Voltage MCB rating - ANSWER 600V
circuit breaker contacts cannot be made of ____ - ANSWER iron. heat breakdown & low
CCA
circuit breaker purpose - ANSWER detect SC/OL and break contact on fault detection
Questions with Complete Solutions
describe (A. trip operating unit ) component function - ANSWER bi-metal/mag. provides
mechanism for detection of fault current and opens contacts
describe (B. control contacts unit ) component function - ANSWER contacts allows the
supply current to flow during normal running when MCB is closed
describe (C. arcing ext. unit ) component function - ANSWER all inclusive factors -
horns, chamber chutes, oils, splitter plates, used to control and extinguish fault arc
describe (D. frame unit ) component function - ANSWER molded case exterior provides
a rigid, mechanically strong, insulated housing for MCB parts
Low Voltage MCB rating - ANSWER 600V
circuit breaker contacts cannot be made of ____ - ANSWER iron. heat breakdown & low
CCA
circuit breaker purpose - ANSWER detect SC/OL and break contact on fault detection
