Sunday, December 27, 2020

Electrician interview Questions & Answers

Electrician interview – There are questions and answers related to circuit breaker. Which are mostly asked in interviews. Hope this helps you.

Electrician interview Questions & Answers

Question 1- What is a circuit breaker?

Answer 1 – Circuit breaker is a mechanical device. Which closes and opens the electrical circuit in normal and abnormal state.

 Question 2 – Which type of circuit breaker?

Answer 2-

1 – Air Circuit Breaker (ACB)

2 – Oil Circuit Breaker (OCB)

3 – Vacuum Circuit Breaker (VCB)

4 – Air Blast Circuit Breaker (ABCB)

5 – SF6 Circuit Breaker

Question 3- How does air circuit breaker work.

Answer 3 – Air circuit breaker is used for law voltage. Occur in abnormal condition or at the time of make and break. The electric arc generated is extinguished with the help of arc chute from normal air. The breaker is accompanied by a protection relay that disconnects the electric circuit from the supply at fault time. It is used for power distribution in PCC panel.

Question 4 – What is the difference between switch and circuit breaker?

Answer 4 – The switch is a device which only opens and closes the circuit in normal condition. The circuit breaker operates in both normal and abnormal state. Can sustain high current during fault time. The circuit breaker can also be operated from the control panel.

Question 5- What is the meaning of making capacity in circuit breaker?

Answer 5– When the circuit breaker is closed then the first kick of the current is called the making capacity of the breaker. The passing during a short circuit is considered to be current. Its value is in KA.

Question 6- How does a vacuum circuit breaker work?

Answer 6 – Vacuum circuit breakers are used for medium voltage from 6.6kv to 33 kv. It uses vacuum to extinguish the electric arc. Vacuum does not contain oxygen, hence spark is not generated. Vacuum pressure is 10-6 torr. Protective relay is mounted on the control panel. Which provides protection to the circuit in an abnormal state.

Electrician interview – There are questions and answers related to circuit breaker. Which are mostly asked in interviews. Hope this helps you.

Question 7- What is the meaning of breaking capacity in a circuit breaker?

Answer 7– The breaking capacity in a circuit breaker is in KA. Breaking capacity of the breaker at the time of fault is called breaking capacity. Which is also called maximum rms value.

Question 8- Which metal is used in VCB contact?

Answer 8- The VCB contact uses silver lead, silver bismuth, copper lead, copper tellurium, metal. Above the contact is the silver lead and silver Telurium.

Question 9- How does SF6 circuit breaker work.

Answer 9– EHV – Used in the supply line from 33 kv to 760 kv. The electric arc in the make and break is quenched with SF6 (sulfur hexa fluoride) gas. In the normal condition, the pressure of SF6 is 6.2 kg / cm 2. This pressure is 14 to 17 kg / cm 2 at the time of operation. They are in both indoor and out door type. Protection relay control panel is installed which provides protection to the electric circuit.

Question 10 – AC circuit breaker is suitable for D.C supply?

Answer 10– Generally AC circuit breakers are not suitable for DC supply. The electric arc is easily extinguished when there is zero in the alternating wave. Where there is no existence of wave in DC, therefore, the value of current is not zero.

Question 11- How does air blast circuit breaker work?

Answer 11– ABCB is used for medium and high voltage (22 kv to 220 kv). In this breaker, the arcs arising at the time of make and break are extinguished by the blast of air. In this, air is compressed and stored in the tank. And the nozzle is used to extinguish sparks at great speed. In any unusual situation, there is a protective relay for protection. Which protects the circuit.

Electrician interview – There are questions and answers related to circuit breaker. Which are mostly asked in interviews. Hope this helps you.

Question 12- How is the selection of circuit breaker done?

Answer 12 –

1 – How much ampere is our constant load. It should be 25% higher capacity breaker.

2 – How many poles need a breaker, this has to be done. It consists of 3P and 4P.

3 – The voltage capacity of the breaker should be constant.

4 – Interrupting capacity should decide which is in mva and ka.

5 – Supply frequency and making capacity of the breaker should go ahead with the offer.

Question 13 – How much is the breaker voltage compared to the line voltage in HT line?

Answer 13 – For a 6.6 kv in HT line, let’s select a breaker of 7.2 kv. There are 12 for 11 kv. 36 kv remains for 33 kv. A breaker of 145 kv is used for 72 kv and 132 kv for 66 kv. Certainly the capacitance of the breaker will be more than the line voltage.

Question 14- How different circuit breakers are named.

Answer 14 – The function of circuit breaker is to extinguish the electric arc occurring at the time of make and break. The media used to extinguish this electric arc has its name on its base. For example, a vacuum circuit breaker uses vacuum to extinguish the arc. And oil is used in oil circuit breakers.

Question 15- How do oil circuit breakers work?

Answer 15 – Oil circuit breaker is used for medium voltage. In this breaker, electric arc arising at the time of fault or at operation is extinguished with oil. The contact of the breaker is immersed in the oil. There are two main functions of oil in it. Acts as an insulator between a contact. Second, when the spark occurs, the heat generated cools quickly. In other words, it also works for cooling. Protection relay is mounted on the control panel. Which protects the circuit.

Question 16- What is the relay setting in air circuit breaker?


ir – Over load setting – This setting is set based on our constant running load. By the way, setting the maximum breaker capacity to 90% is considered correct.

isd – short circuit – The setting of the short circuit is based on the over load setting. The winning setting is done four times more than it loads. In other words, if the overload setting is 1000 amperes, then the short circuit setting is 4000 amperes.

ig – ground fault – usually set at 40% of the capacity of the pay breaker.

All three of the above (ir, isd, ig) have settings along with time setting.

ii – Instantaneous Current – As much as the current is set there, the breaker will be tripped immediately. There is no time setting in this.

Question 17 – What is the Anti Pumping contactor in the breaker?

Answer 17 – Anti Pumping Contactor is in every breaker. Its main function is that the breaker does not get the closing command once after the closing command. Therefore, anti-pumping contactors are used.

If there is a fault in the line The breaker will be tripped as soon as it closes. In such a situation, the operator presses the push button and the breaker will get the command of closing again after tripping. And if it repeats, it damages the breaker. Therefore, anti-pumping contactor is applied.

Question 18 – What is MCCB? How does it work?

Answer 18Full Form of MCCB – Module Case Circuit is Breaker. MCCB

He is the most commonly used circuit breaker in industries. 125 Amp. It has a rating of 800 ampere. And is used in low voltages 120 Used up to 450 volts. There are two types of MCCB available, one is thermal base protection and the other is microprocessor base protection. MCCB has protection like overload, short circuit, earth fault. Which we can set according to our requirement.

Question 19 – what is the difference between fuse and circuit breaker?

Answer 19 –

Fuse – The fuse has a wire according to its capacity. Which melts when the temperature increases due to over load and short circuit. Once the element of the fuse is blown, it is not used again. The fuse itself is replaced.

Circuit Breaker – The circuit breaker consists of a bimetal strip. Which breaks the circuit at the time of over current and short circuit. It can be reset and turned on.

Electrician interview – There are questions and answers related to circuit breaker. Which are mostly asked in interviews. Hope this helps you.

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