2-28
Figure 2-24.—Push-button circuit breaker.
You will find other physical types of circuit breakers as you work with electrical circuits. They are
found in power distribution systems, lighting panels, and even on individual pieces of equipment.
Regardless of the physical size and the amount of power through the circuit breaker, the basic operating
principles of circuit breakers apply.
Q33. What is a trip-free circuit breaker?
Q34. What is a nontrip-free circuit breaker?
Q35. Where should you use a trip-free circuit breaker?
Q36. Where should you use a nontrip-free circuit breaker?
The magnetic trip element makes use of a magnetic element (electromagnet). If current reaches a
preset quantity, the magnetic element attracts the trip bar and releases the latch.
The thermal-magnetic trip element combines the actions of the bimetallic and magnetic elements in a
single trip element. If either the bimetal element or the magnetic element reacts, the circuit breaker will
trip.
Q37. What are the three time delay ratings for circuit breakers?
Q38. What is selective tripping and why is it used?
Q39. If the power distribution system shown in figure 2-22 uses selective tripping, what is the time delay
rating for each of the circuit breakers shown?
Q40. What factors are used to select a circuit breaker?
Q41. What type of circuit breaker is used on a multimeter?
CIRCUIT BREAKER MAINTENANCE
Circuit breakers require careful inspection and periodic cleaning. Before you attempt to work on
circuit breakers, check the applicable technical manual carefully. When you work on shipboard circuit
breakers, the approval of the electrical or engineering officer must be obtained before starting work. Be
certain to remove all power to the circuit breaker before you work on it. Tag the switch that removes the
power to the circuit breaker to ensure that power is not applied while you are working.
Once approval has been obtained, the incoming power has been removed, the switch tagged, and you
have checked the technical manual, you may begin to check the circuit breaker. Manually operate the
circuit breaker several times to be sure the operating mechanism works smoothly. Inspect the contacts for
