Q2
(a) Describe the circuit breaker for an a.c. generator using a sketch to show how arcing is Controlled.
(4)
(b) Explain the sequence of events that might occur if the breaker opens on a short circuit and state the check you would require following such event
(4)
(c) Give a safe procedure to follow should a main circuit breaker fail to open under fault Condition
(4)
Reference Answer
### Part (a): AC Generator Circuit Breaker and Arc Control An Air Circuit Breaker (ACB) is commonly used for the protection and switching of main AC generators on board ships. Its primary function is to interrupt normal load currents as well as high fault currents, such as those from a short circuit. A critical design feature is its ability to safely extinguish the powerful electric arc that forms when its contacts separate under load. **Construction and Operation:** * **Main Components:** An ACB consists of a robust frame, a spring-charged operating mechanism, fixed and moving main contacts, arcing contacts, and an arc chute assembly positioned above the contacts.
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