Circuit Breakers and Relays

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Q1: Which circuit breaker is installed along with wiring circuit against leakage current protection?

• OCB
• MCB
• ELCB
• MCCB

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Q2: Which relay hold their contacts in position after power is cutoff?

• Read relay
• Current relay
• Voltage relay
• Latching relay

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Q3: What is the name of circuit breaker?

• Oil circuit breaker
• Air blast circuit breaker
• Vacuum circuit breaker
• Air break circuit breaker

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Q4: How the rupturing capacity of circuit breaker is rated?

• KV
• KW
• MVA
• KVAR

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Q5: What is the pick-up voltage in a over voltage relay indicated?

• Working voltage of relay
• Maximum voltage rating of relay
• Minimum voltage rating of relay
• Minimum voltage to start the relay

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Q6: What is the function of Buchholz relay in power transformer?

• Over load and short circuit protection
• Over voltage and earth fault protection
• Open circuit and earth fault protection
• Open circuit and over voltage protection

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Q7: Which type of load is protected by 'G' series MCB?

• Ovens
• Geysers
• Air conditioners
• General lighting systems

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Q8: Which type of relay is used in both A.C and D.C supply?

• Reed relay
• Impulse relay
• Thermal relay
• Clapper-type armature relay

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Q9: Which circuit breaker is used as a switch and protective device in the domestic wiring circuit?

• Air circuit breaker
• Miniature circuit breaker
• Moulded case circuit breaker
• Earth Leakage circuit breaker

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Q10: What is the purpose of trip coil used in circuit breakers?

• Easy operation
• Remote operation
• Accurate operation
• Emergency operation

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Q11: What is the function of relay to the breaking operation of circuit breaker in control circuit?

• Sensing the fault quantities
• Analyzing the condition of breaker
• Controlling the Speed in case of fault
• Interpreting the fault situation to operate breaker

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Q12: What is the effect, if the test button marked as 'X' is closed permanently in ELCB?

• Circuit trips intermittently
• Circuit functions normally
• Circuit switch off completely
• Circuit will not trip on leakage

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Q13: What is the defect in an air circuit breaker, if trips intermittently on loading?

• Incorrect setting of relay
• Excessive heat
• Insufficient air pressure
• Line voltage is too high

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Q14: What is the defect in a oil circuit breaker if the oil heats up excessively?

• Line voltage is too high
• Excessive load
• Poor dielectric strength
• Defective tripping mechanism

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Q15: What is the cause for the defect if phase to ground fault on the transmission line?

• Components failure
• Insulation failure
• Human error
• Fuse failure

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