Protection Devices Unit 15 54 Fuse 12. tuse consists of an element electrically

Question

Protection Devices Unit 15 54 Fuse 12. tuse consists of an element electrically connectedto nd Nades, which is enclosed In a tube and surrounded by a filler material. al conductive al foam cy ight Magnetic time-delay circuit breakers operate on the sole- noid principle where a movable core, held with a spring,is moved by the magnetic field of ain)-- a) overload b) short circui c) ground fault d) b or c t a fire, a nonconductive 15.6 Circuit Breaker Types As current flows through the element of a fuse, it gen 13. erates heat. When a sustained overload occurs, the heat nelts stopping the flow of current. al several elements breakers aperate on the principle that as the cur- rent increases, the time it takes for the device toen decreases ersely pro- he greater protection all of the elements , a portion of the element idi none of these la) Inverse time b) Adjustable trip c) Instantaneous trip di all of these n When a short circuit or ground fault occurs, melts), 14 breakers permit the thermal trip setting to be rmoing the load from the source very quickly. al several elements bi all of the elements ci a portion of the element d none of these adjusted to coordinate the circuit breaker's operation with other protection devices a) Inverse time (b) Adjustable trip c) Instantaneous trip (d) all of these that as the ce to apen 155 Circuit Breaker Trip Elements 15. breakers operate on the principle of electromagne The sensing element causes the circuit breaker open when a predetermined calibration temperature is tism only and are used for very large motors a Inverse time b) Adjustabile thp c) Instantaneous trip parts from imped- o facilitate reached w aj magnetic bi electronic id) all of these thermal ld none of these 199 Mike Holt Enterprises, Inc. www.MikeHolt.com 888.NEC.CODE (632.2633)

Explanation / Answer

8) Option d is corrct: It must be non conducting to avoid sparking and fire

9) all of the elements( option b is correct) . when fuse melts cirucit open and current is zero

10) Option C is correct ( a portion of the fuse element will melt)

11 Option c is correct ( Thermal sensing element)

12) Option d is correct(both for short and ground faults0

13) Inverse time relay (option a is correcct). In this time is inversially proportional to fau;t current

14)Option C is corrcect . adjustable trip

15)all of the above. all are electromagnetic relays (option d is correct)

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