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单选题
术语Circuit breaker意为（）。
A
电路板断路器
B
电路板控制器
C
电路板装置
D
电路板箱
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any pointer positionDue to failure of one of the carbon brushes the excitation voltage is lost on one alternator that operating in parallel.Then that alternator will()
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You are attempting to parallel two AC.generators, and the synchroscope pointer revolving in the fast direction.This indicates that the frequency of the incoming machine is
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An alternator is being paralleled with one on the line At the instant the circuit breaker is close, the frequency of the incoming alternator will normallyA.increaseB.not changeC.decreaseD.be exactly 60 hertz
考题
A circuit breaker and a fuse have a basic similarity(类似) in that they both ______.A.can be reset to energize the circuitB.should open the circuit when overloadedC.will burn out when an over current flow developsD.should short the circuit when overloaded
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A circuit breaker and a fuse have a basic similarity in that they both______.A.can be reset to energize the circuitB.should open the circuit when overloadedC.will burn out when an over current flow developsD.should short the circuit when overloaded
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A circuit breaker differs from a fuse in that a circuit breaker ______.A.melts and must be replacedB.is enclosed in a tube of insulating material with metal ferrules(环) at each endC.gives no visual indication of having opened the circuitD.trips to break the circuit and may be reset
考题
If an attempt is made to hoist a load that exceeds the capacity of an electric winch，an overload safety device causes a circuit breaker to cut off the current to the winch motor ______．A.when the line pull reaches the rated winch capacityB.after the line pull exceeds the rated winch capacityC.after a short build-up of torqueD.immediately
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单选题Running an electric winch at slow speed over a long period of time causes（）.A
the speed to be retarded by the friction brakeB
a load to go downward at full speedC
the circuit breaker to turn offD
the resistors to overheat and eventually burn out
考题
单选题Before any work on electrical or electronic equipment is performed, which of the following precautions should be carried out （）A
De-energize the applicable switchboard busB
Bypass the interlocksC
Secure and tag the supply circuit breaker in the open positionD
Station a man at the circuit supply switch
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单选题The purpose of a main switchboard circuit breakers reverse-power trip is to （）.A
prevent main circuit overloadB
protect the circuit breaker blowout coilC
prevent alternator motorizationD
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单选题A ground in an electrical circuit outside the engine room （）.A
cannot be detected tinder normal conditionsB
is of no consequence to engineering personnelC
is indicated at the branch circuit breaker panelD
is indicated by the ground detecting lamps on the main switchboard
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单选题A diesel generator has just been paralleled with an AC turbo-generator, but the load can not be properly divided.This could be caused by（）A
an incorrect diesel generator governor speed droop adjustmentB
a faulty reverse power relay within the main circuit breaker assemblyC
unsynchronized isochronous load distribution adjustmentsD
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单选题Which of the listed precautions should be taken when cleaning the internals of a motor with compressed air?（）A
Open the machine on both ends so as to allow the air and dust to escapeB
Be certain that the circuit breaker is opened and tagged on the feeder panelC
Be certain that the air is clean and as dry as possibleD
All of the above
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单选题Fuses placed in series with a thermal trip-type circuit breaker are used for （）.A
time-delay protectionB
short-circuit protectionC
short duration surge protectionD
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单选题A circuit breaker and a fuse have a basic similarity in that they both （）.A
can be reset to energize the circuitB
should open the circuit when overloadedC
will burn out when an over current flow developsD
All of the above
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单选题A circuit breaker differs from a fuse in that a circuit breaker （）.A
melts and must be replacedB
is enclosed in a tube of insulating material with metal ferrules at each endC
gives no visual indication of having opened the circuitD
trips to break the circuit and may be reset
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单选题You are attempting to parallel two AC generators, and the syncope pointer is revolving in the fast directionThis indicates that the frequency of the incoming machine is （）.A
higher than the bus frequencyB
lower than the bus frequencyC
the same as the bus frequency but out of phase with itD
the same as the bus frequency and the circuit breaker may be closed at any pointer position
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