Define the following terms related to circuit breaker. 1) Breaking Capacity 2) Making Capacity 3) Short time rating and 4) Normal current rating

Define the following terms related to circuit breaker. 1) Breaking Capacity 2) Making Capacity 3) Short time rating and 4) Normal current rating
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1 Answer

Answer :

1) Breaking Capacity: It is current (r.m.s) that a circuit breaker is capable of breaking at given recovery voltage under specified conditions (e.g. power factor, rate of rise of restriking voltage). 

2) Making Capacity: The peak value of current (including d.c. component) during the first cycle of current wave after the closure of circuit breaker is known as making capacity. 

3) Short Time Rating: It is the period for which the circuit breaker is able to carry fault current while remaining closed. 

4) Normal Current Rating: It is the r.m.s. value of current which the circuit breaker is capable of carrying continuously at its rated frequency under specified conditions. The only limitation in this case is the temperature rise of current-carrying parts.

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Related questions

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Last Answer : Insulation level - it is the combination of rated voltage, the corresponding impulse withstand voltage, which together characterize the insulation of the equipment as regards its ability to withstand ... wave of power frequency (50 Hz) which the insulation of equipment should withstand. 

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

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

Making capacity of the circuit breaker depends on

Description : Making capacity of the circuit breaker depends on (A) operating voltage (B) short circuit MVA (C) fault current (D) All of the above

Last Answer : Making capacity of the circuit breaker depends on (A) operating voltage (B) short circuit MVA (C) fault current (D) All of the above

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Description : A 3-phase circuit breaker is rated at 1250 A, 2000 MVA, 33 kV, 4s. Its making current capacity will be   (a) 35 kA (b) 89 kA (c) 79 kA (d) 69 kA

Last Answer : 89

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Description : Why asymmetrical breaking current is higher than the symmetrical breaking current in a circuit breaker?

Last Answer : Asymmetrical breaking current is the rms value of the combined sum of the dc and ac components of the short circuit current at the instant of separation of the breaker contacts while ... the ac component alone. Thus asymmetrical breaking current is higher than the symmetrical breaking current.

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Description : A three-phase, 33 kV oil circuit breaker is rated 1200 A, 2000 MVA, 3 s. The symmetrical breaking current is  (A) 1200 A (B) 3600 A (C) 35 kA (D) 104.8 kA

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Description : Which of the following precautions should be taken when a blown fuse, rated at 10 amperes, is replaced? A. Short out the fuse before removing it from the circuit. B. Use needle-nose pliers to ... D. Fuses of 10 ampere rating and less are virtually harmless when energized and may be handled freely.

Last Answer : Answer: C

The fuse rating is expressed in terms of?

Last Answer : The fuse rating is expressed in terms of current.

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Description : Explain construction and working of SF6 circuit breaker.

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Last Answer : Earth Leakage circuit breaker (ELCB) works on the basis of Residual current

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

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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

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

A circuit breaker is designed to protect an electrical circuit from damage caused by :

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

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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

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

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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) 

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

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

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Last Answer : Arc in a circuit breaker is interrupted at zero current.

The arc voltage produced in A.C. circuit breaker is always?

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

In a circuit breaker the basic problem is to?

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

Ionization in circuit breaker is facilitated by?

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

The voltage appearing across the contacts after opening of the circuit breaker is called______voltage.

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

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

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Last Answer : Magnetic circuit breaker has instantaneous trip action.

Thermal circuit breaker has?

Last Answer : Thermal circuit breaker has delayed trip action.

The arcing contacts in a circuit breaker are made of?

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

what is SF6 circuit breaker?

Description : what is SF6 circuit breaker?

Last Answer : SF6 is Sulpher hexa Fluoride gas. If this gas is used as arc quenching medium in a Circuit breaker means SF6 CB.

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Description : Write down the circuit breaker with their rating used in traction substation. Explain any one.

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Description : Why circuit breaker connect b)w two transformer  (same rating

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Description : The capacity of a battery is expressed in terms of A. Current rating B. Voltage rating C. Ampere hour rating D. None of the above

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Description : For a traction transformer circuit breaker state: 1) Rated current and rupturing capacity 2) Any two tests it should be capable of withstanding 3) Overall tripping time and relay time.

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Last Answer : Making capacity = 2.55 times symmetrical breaking capacity.  

Define the following terms with respect to protective relays i) Relay time ii) Reset current iii) Plug setting multiplier and iv) Time setting multiplier

Description : Define the following terms with respect to protective relays i) Relay time ii) Reset current iii) Plug setting multiplier and iv) Time setting multiplier

Last Answer : 1) Relay Time: The time interval between occurrence of fault and closure of relay contacts.  2) Reset Current: The value of current below which the relay resets and comes back to ... The adjustment arrangement provided for setting the operation time of relay is known as Time setting multiplier. 

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Description : In order to reduce the voltage surges due to current chopping and capacitive current breaking, we connect (A) A resistor across the CB contacts. (B) A capacitor across the CB contacts. (C) An inductor across the CB contacts. (D) A switch across the CB contacts

Last Answer : In order to reduce the voltage surges due to current chopping and capacitive current breaking, we connect A resistor across the CB contacts.

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

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

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

In the induction type directional over current relay, when a short-circuit occurs in the circuit

Description : In the induction type directional over current relay, when a short-circuit occurs in the circuit (A) power flows in reverse direction (B) power flows in normal direction (C) directional power element does not operate (D) over current element is not energized

Last Answer : In the induction type directional over current relay, when a short-circuit occurs in the circuit power flows in reverse direction

In which fault the maximum short circuit current occurs?

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

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

Making current of a circuit breaker refers to:

Description : Making current of a circuit breaker refers to: (1) Steady state rated current (2) Average value of transient short circuit current (3) R.M.S. value of the short circuit current at the the time of major peak (4) Equal to the fault current

Last Answer : Making current of a circuit breaker refers to: R.M.S. value of the short circuit current at the the time of major peak

Fuses placed in series with a thermal trip-type circuit breaker are used for _____________. A. time-delay protection B. short-circuit protection C. short duration surge protection D. sustained overload protection

Description : Fuses placed in series with a thermal trip-type circuit breaker are used for _____________. A. time-delay protection B. short-circuit protection C. short duration surge protection D. sustained overload protection

Last Answer : Answer: B

A relay has a rating of 5 A, 2.2 sec IDMT and a relay setting of 125% TMS = 0.6. It is connected to a supply

Description : A relay has a rating of 5 A, 2.2 sec IDMT and a relay setting of 125% TMS = 0.6. It is connected to a supply circuit through a C.T. 400/5 ratio. The fault current is 4000 A. The operating current of the relay is

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The short circuit in any winding of the transformer is the result of?

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

When a fluorescent lamp has reached the end of its useful life, it should be replaced immediately, or the resultant flashing may _____________. A. blow the lamp's circuit breaker B. explode, causing glass to fly in all directions C. short circuit the ballast transformer D. damage the starter and the ballast

Description : When a fluorescent lamp has reached the end of its useful life, it should be replaced immediately, or the resultant flashing may _____________. A. blow the lamp's circuit breaker B. explode, ... fly in all directions C. short circuit the ballast transformer D. damage the starter and the ballast

Last Answer : Answer: D

Electric circuits are protected against overloads and short circuits by means of a/an ______________. A. circuit breaker B. amplifier C. diode D. capacitor

Description : Electric circuits are protected against overloads and short circuits by means of a/an ______________. A. circuit breaker B. amplifier C. diode D. capacitor

Last Answer : Answer: A

The arc resulting from the tripping of a circuit breaker is prevented from damaging the contacts by _____________. A. designing the contacts to open slowly B. directing the arc into an arc chute C. an inverse timed thermal trip for short circuit currents D. instantaneous magnetic trip for overload currents

Description : The arc resulting from the tripping of a circuit breaker is prevented from damaging the contacts by _____________. A. designing the contacts to open slowly B. directing the arc into an ... an inverse timed thermal trip for short circuit currents D. instantaneous magnetic trip for overload currents

Last Answer : Answer: B

A molded-case circuit breaker provides protection against short circuits by using a/an ________________. A. electromagnet B. shading coil C. arc quencher D. burn away strip

Description : A molded-case circuit breaker provides protection against short circuits by using a/an ________________. A. electromagnet B. shading coil C. arc quencher D. burn away strip

Last Answer : Answer: A

Air blast circuit breaker is used for (a) over currents (b) short duty (c) intermittant duty (d) repeated duty

Description : Air blast circuit breaker is used for (a) over currents (b) short duty (c) intermittant duty (d) repeated duty

Last Answer : (d) repeated duty