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Arc in a circuit breaker is interrupted at zero current.

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Description : The arc temperature in Oil Circuit Breaker may reach up to_______.  (A) 5,000° K (B) 8,000° K (C) 10,000° K (D) None of the above

Answer : The arc temperature in Oil Circuit Breaker may reach up to 5,000° K 

Answer : The arc voltage produced in A.C. circuit breaker is always in phase with the arc current.

Description : The arc voltage in a circuit breaker is :

Answer : The arc voltage in a circuit breaker is : in phase with the arc current

Description : Which of the following is used in a circuit breaker as the medium in which the arc forms? A) Insulating gas B) Insulating oil C) Vacuum D) All the above

Answer : Which of the following is used in a circuit breaker as the medium in which the arc forms? A) Insulating gas B) Insulating oil C) Vacuum D) All the above

Description : Arc in a circuit behaves as?

Answer : Arc in a circuit behaves as a resistance decreasing with voltage rise across the arc.

Description : The number of cycles in which a high speed circuit breaker can complete its operation is  (A) 3 to 8 (B) 10 to 18 (C) 20 to 30 (D) 40 to 50

Answer : The number of cycles in which a high speed circuit breaker can complete its operation is 3 to 8

Answer : In a circuit breaker the basic problem is to transmit large power.

Answer : Ionization in circuit breaker is facilitated by high temperature, increase of mean free path, increasing field strength.

Answer : The arcing contacts in a circuit breaker are made of copper tungsten alloy.

Description : A circuit breaker is designed to protect an electrical circuit from damage caused by :  (A) Over load (B) Short circuit (C) Over current (D) All of the above

Answer : A circuit breaker is designed to protect an electrical circuit from damage caused by :  (A) Over load (B) Short circuit (C) Over current (D) All of the above

Description : The Minimum Oil Circuit Breaker (MOCB) is named because of :  (A) Reduced requirement of oil (B) Reduced requirement of air (C) All of the above (D) None of the above

Answer : The Minimum Oil Circuit Breaker (MOCB) is named because of : Reduced requirement of oil 

Description : For selecting a circuit breaker, ______ should be determined.  (A) initial current that flows on occurrence of a short circuit only (B) transient current that flows at the time of circuit interruption only (C) resonant frequency only (D) (A) and (B) 

Answer : For selecting a circuit breaker, ______ should be determined. (A) initial current that flows on occurrence of a short circuit only (B) transient current that flows at the time of circuit interruption only (C) resonant frequency only (D) (A) and (B) 

Description : ln a minimum oil circuit breaker the oil is used

Answer : ln a minimum oil circuit breaker the oil is used to act as circuit breaking medium only

Answer : The voltage appearing across the contacts after opening of the circuit breaker is called recovery voltage.

Answer : Air blast circuit breaker is used for repeated duty.

Answer : Magnetic circuit breaker has instantaneous trip action.

Answer : Thermal circuit breaker has delayed trip action.

Description : what is SF6 circuit breaker?

Answer : A circuit breaker in which SF6 under pressure gas is used toextinguish the arc is calledSF6 circuit breaker. SF6 (sulphur hexafluoride) gas has excellent dielectric , arc quenching, chemical and other physical properties and has proved its ...

Description : Breaking capacity of a circuit breaker is usually expressed in terms of  (1) Ampere (2) Volts (3) MW (4) MVA

Answer : Breaking capacity of a circuit breaker is usually expressed in terms of MVA

Description : Explain working of static AC circuit breaker. 

Answer : Static AC Circuit breaker: The circuit configuration of static AC circuit breaker using SCR is shown in the figure. When switch S' is closed, the SCRs T1 and T2 are fired in positive ... non-availability of gate current. Thus the maximum time delay for breaking the circuit is one half-cycle.

Description : Explain working of AC circuit breaker using SCR with circuit diagram.

Answer : AC Circuit Breaker:  The circuit configuration of static AC circuit breaker using SCR is shown in the figure. When switch S' is closed, the SCRs T1 and T2 are fired in positive ... to non-availability of gate current. Thus the maximum time delay for breaking the circuit is one half-cycle.

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Description : Write the purpose of coal and ash handling unit. Also write different activities that arc carried out in this unit.

Answer : Purpose of coal and ash handling unit :-  To transport coal from coal storage to power plant. A large quantity of ash about 10 to 30 % produced in furnace, the removal of ash from boiler furnace ... disposed off.  Various methods of disposal of ash:  Mechanical system.  Pneumatic system.

Description : Compare the AC and DC Arc lamps.

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Description : Arc resistance  (1) increases with increase in arc current (2) decrease with increase in arc current (3) is independent of arc current (4) is independent of arc length

Answer : Arc resistance decrease with increase in arc current 

Description : For arc welding current range is usually  (1) 10 to 15 A (2) 30 to 40 A (3) 50 to 100 A (4) 100 to 350 A

Answer : For arc welding current range is usually 100 to 350 A

Description : Identify the correct combination of respective Electric arc welding and Electric resistance welding methods :  (A) Butt welding and Seam welding  (B) Hydrogen shielding and Projection welding  (C) Seam welding and Coated electrode welding  (D) Coated electrode welding and Hydrogen shielding

Answer : Identify the correct combination of respective Electric arc welding and Electric resistance welding methods :  (A) Butt welding and Seam welding  (B) Hydrogen shielding and Projection welding  ... Seam welding and Coated electrode welding  (D) Coated electrode welding and Hydrogen shielding

Description : The supply for arc welding is : 

Answer : The supply for arc welding is : Low voltage, high current ac or dc voltage

Description : Which of the following medium is employed for extinction of arc in air circuit breaker ?(a) Water (b) Oil(c) Air (d) SF6

Answer : Which of the following medium is employed for extinction of arc in air circuit breaker ?(a) Water (b) Oil(c) Air (d) SF6

Answer : A fuse in a motor circuit provides protection against short-circuit and overload.

Answer : Air blast circuit breakers for 400 kV power system are designed to operate in 50 millisecond.

Answer : The short circuit in any winding of the transformer is the result of impulse voltage.

Answer : The time of closing the cycle, in modern circuit breakers is 0.003 sec.

Description : The current zero interruption, in oil and air blast circuit breakers, is achieved by?

Answer : The current zero interruption, in oil and air blast circuit breakers, is achieved by lengthening of the gap, cooling and blast effect.

Description : In which fault the maximum short circuit current occurs?

Answer : In three phase bolted fault the maximum short circuit occurs.

Description : If the % reactance upto the fault point is 20%, then the short circuit current will be

Answer : If the % reactance upto the fault point is 20%, then the short circuit current will be 5 times the full load current

Description : Which of the following circuit breakers has high reliability & minimum maintenance?  (A) Bulk oil type CB (B) Air blast CB (C) Vacuum CB (D) Sulphur hexafluoride CB 

Answer : Which of the following circuit breakers has high reliability & minimum maintenance?  (A) Bulk oil type CB (B) Air blast CB (C) Vacuum CB (D) Sulphur hexafluoride CB 

Description : The following is/are the characteristics of SF6 circuit breakers:  (A) It does not need an auxiliary breaking chamber (B) Short break time of 2 to 2.5 cycles (C) All of the above (D) None of the above

Answer : The following is/are the characteristics of SF6 circuit breakers:  (A) It does not need an auxiliary breaking chamber (B) Short break time of 2 to 2.5 cycles (C) All of the above (D) None of the above

Answer : Circuit breakers are essentially current carrying contacts called electrodes.

Answer : Circuit breakers usually operate under transient state of short-circuit current.

Description : In parallel RLC resonance circuit at resonance the current will be  (1) Minimum (2) Maximum (3) Zero (4) Infinite

Answer : In parallel RLC resonance circuit at resonance the current will be Minimum 

Description : In a series RLC high Q circuit, the current peaks at a frequency  (1) equal to the resonant frequency (2) greater than the resonant frequency (3) less than the resonant frequency (4) equal to half the resonant frequency

Answer : In a series RLC high Q circuit, the current peaks at a frequency equal to the resonant frequency

Description : In a series L-C circuit at the resonant frequency the?

Answer : In a series L-C circuit at the resonant frequency the current is maximum.

Description : Magnitude of current at resonance in R-L-C circuit?

Answer : The current will be maximum if it is a series rlc circuit.

Description : The power factor at resonance in R-L- C parallel circuit is?

Answer : since a rlc circuit at resonance behaves like a pure resistive circuit, i.e there is no phase difference between current and voltage, hence the power factor is unity.

Description : At ______ frequencies the parallel R-L circuit behaves as purely resistive.

Answer : At very high frequencies the parallel R-L circuit behaves as purely resistive.

Description : At very low frequencies a series R-C circuit behaves as almost purely?

Answer : At very low frequencies a series R-C circuit behaves as almost purely capacitive.

Answer : If a D.C. shunt motor is working at full load and if shunt field circuit suddenly opens this will make armature to take heavy current, possibly burning it.

Answer : When the total impendance equals  supply frequency.

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