ELECTRICAL INTERVIEW QUESTIONS AND ANSWERS FOR FRESHERS PDF

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Electrical Interview Questions And Answers For Freshers Pdf

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ELECTRICAL INTERVIEW QUESTIONS AND ANSWERS. Visit nuratermege.ml more resources. 1. What happens if I connect a capacitor to a generator load?. India's No.1 Job Portal for freshers - nuratermege.ml . Review a list of frequently asked Electrical interview questions for electrical graduates. Frequently asked interview questions with answers under the subjects like electrical machines. EEE_ Technical Interview Questions. 1. How can you relate power engineering with electrical engineering? The most common cause is single-phasing.

So we can understand the importance of power measurement through power quality meters. What is the different between digital phase converter and ordinary phase converter? Digital phase converter are a recent development in phase converter technology that utilizes proprietary software in a powerful microprocessor to control solid state power switching components.

This microprocessor, called a digital signal processor DSP , monitors the phase conversion process, continually adjusting the input and output modules of the converter to maintain perfectly balanced three-phase power under all load conditions.

Explain the operation of variable frequency transformer? A variable frequency transformer is used to transmit electricity between two asynchronous alternating current domains. A variable frequency transformer is a doubly-fed electric machine resembling a vertical shaft hydroelectric generator with a three-phase wound rotor, connected by slip rings to one external ac power circuit.

1. Why we use 3-phase supply? Why are not 4 or something else?

A direct-current torque motor is mounted on the same shaft. Changing the direction of torque applied to the shaft changes the direction of power flow; with no applied torque, the shaft rotates due to the difference in frequency between the networks connected to the rotor and stator. The variable frequency transformer behaves as a continuously adjustable phase-shifting transformer.

It allows control of the power flow between two networks. What is the main use of rotary phase converter? Rotary phase converter will be converting single phase power into true balanced 3 phase power,so it is often called as single phase to three phase converter. Often the advantages of 3 phase motors, and other 3 phase equipment, make it worthwhile to convert single phase to 3 phase so that small and large consumers need not want to pay for the extra cost of a 3 phase service but may still wish to use 3 phase equipment.

Use of switch mode power converter in real-time basis? Switch mode power converter can be used in the following 5 different ways step down an unregulated dc input voltage to produce a regulated dc output voltage using a circuit known as Buck Converter or Step-Down SMPS, step up an unregulated dc input voltage to produce a regulated dc output voltage using a circuit known as Boost Converter or Step-Up SMPS, step up or step down an unregulated dc input voltage to produce a regulated dc output voltage, invert the input dc voltage using usually a circuit such as the Cuk converter, and produce multiple dc outputs using a circuit such as the fly-back converter.

Which type of oil is used as a transformer oil? Transformer oil, or insulating oil, is usually a highly-refined mineral oil that is stable at high temperatures and has excellent electrical insulating properties.

It is used in oil filled transformers, some types of high voltage capacitors, fluorescent lamp ballasts, and some types of high voltage switches and circuit breakers. Its functions are to insulate, suppress corona and arcing, and to serve as a coolant. Well into the s, polychlorinated biphenyls PCB s were often used as a dielectric fluid since they are not flammable. They are toxic, and under incomplete combustion, can form highly toxic products such as furan.

Starting in the early s, concerns about the toxicity of PCBs have led to their banning in many countries. Today, non-toxic, stable silicon-based or fluoridated hydrocarbons are used, where the added expense of a fireresistant liquid offsets additional building cost for a transformer vault. Combustion-resistant vegetable oil-based dielectric coolants and synthetic pentaerythritol tetra fatty acid C7, C8 esters are also becoming increasingly common as alternatives to naphthenic mineral oil.

Esters are non-toxic to aquatic life, readily biodegradable, and have a lower volatility and higher flash points than mineral oil. If we give A, V on Primary side of 1. Mcb specification are done on maximum current flow in circuit. What is the full form of KVAR? What is excitation?

Excitation is applying an external voltage to DC shunt coil in DC motors. In three pin plug 6 Amp. Because Current flow in the conductor is inversely proportional to the conductor diameter. So if any short circuits occur in the system first high currents bypassed in the Earthling terminal. Difference between megger test equipment and contact resistance meter test instruments?

Megger test equipment used to measure cable electric resistance, conductor continuity, phase identification where as contact resistance meter test instruments used to measure low resistance like relays ,contactors. When we connect the large capacitor bank in series? So in order to bring the voltage at the load terminals within its limits i. What is electrical diversity factor in electrical installations? Electrical diversity factor is the ratio of the sum of the individual maximum demands of the various subdivisions of a system, or part of a system, to the maximum demand of the whole system, or part of the system, under consideration.

Electrical diversity factor is usually more than one. Why field rheostat is kept in minimum position while armature rheostat at maximum position? In motors at the time of starting the armature resistance is introduced to reduce the high starting current and the field resistance is kept minimum to have high starting torque.

Why computer humming sound occurred in HT transmission line? This computer humming sound is coming due to ionization breakdown of air into charged particles of air around transmission conductor. This effect is called as Corona effect, and it is considered as power loss.

Electrical Engineering Questions and Answers

Explain What is rated speed? At the time of motor taking normal current rated current the speed of the motor is called rated speed.

It is a speed at which any system take small current and give maximum efficiency. What is different between resistance grounding system and resistance earthing system? Resistance grounding system means connecting the neutral point of the load to the ground to carry the residual current in case of unbalanced conditions through the neutral to the ground whereas resistance earthing system is done in an electric equipment in order to protect he equipment in occurrence of fault in the system.

Why should be the frequency 50 Hz 60Hz only why not others like 45, 95 56 or anything , why should we maintain the frequency constant if so why it is only 50 Hz 60Hz? We can have the frequency at any frequency you like, but than you must also make your own motors,high voltage transformers or any other equipment you want to use.

How to determine alternating current frequency? Zero crossings of the sine wave to trigger a monostable pulse generator is a way to determine alternating current frequency.

A fixed width pulse is generated for each cycle. The more pulses there are per second, the more the energy. The pulses are integrated filtered or averaged to get a steady DC voltage which is proportional to frequency. This voltage can then be displayed on an analogue or digital voltmeter, indicating frequency. This method is more suitable than a direct counter, as it can get good accuracy in a second or so. Why electricity in India is in the multiples of 11 like 11kv, 22kv, 33kv?

Transformer Induced voltage equation contains 4. So always transmission voltage is multiple of 11 Why we use ac system in India why not dc?

Secondly it is much easier to change the voltage of AC electricity for transmission and distribution. When a fault on the network occurs, a large fault current occurs. In an AC system this becomes much easier to interupt, as the sine wave current will naturally tend to zero at some point making the current easier to interrupt. Which type of motor is used in trains, what is the rating of supply used explain Working principal?

Dc series is in the trains to get high starting torque while starting of the trains and operating voltage is v dc. Battery banks are in connected in series or parallel and why? Battery banks are always connected in series in order to get a multiplied voltage where the AH or current capacity remaining same.

Electrical engineering Interview Questions and Answers

Ex : 24 nos. What is inrush current? Inrush current is the current drawn by a piece of electrically operated equipment when power is first applied. It can occur with AC or DC powered equipment, and can happen even with low supply voltages. In a Tap changing transformer where is the tap connected, is it connected in the primary side or secondary side? Tapings are connected to high voltage winding side, because of low current. If we connect tapings to low voltage side, sparks will produce while tap changing operation due to high current.

Why transformer ratings are in kva? Since the power factor of transformer is dependent on load we only define VA rating and does not include power factor. In case of motors, power factor depend on construction and hence rating of motors is in KWatts and include power factor.

Define what is difference between fuse and breaker? Fuses are burned at the time of over current flows in the circuit but breakers are just open not burn at the time of over current flow. Fuses are used in only one time but breakers are used by multiple number of times. What is the difference between delta-delta, delta-star transformer? Delta-star is a distribution kind of transformer where from secondary star neutral is taken as a return path and this configuration is used for Step down voltage phenomena.

Capacitor is load free component but why ampere meter shows current when capacitor bank breaker close? As we know that Electrical is having two type of load, Active and Reactive. Traction implies with the electric power for traction system i. Now a day, magnetic traction is also utilised for bullet trains. Essentially dc motors are utilized for electric traction systems.

Pu stands for per unit in power system. Circuit Breaker is one which makes or breaks the circuit. ONAN oil natural. Power factor should be high in order to get smooth operation of the system. Arc is extinguished by the Arc Quenching media like air.

Under normal condition the moving contact comes in contact with fixed contact thereby forming the closed contact for the flow of current. Rotory exciter is an additional small generator mounted on the shaft of main generator.

Purpose of exciter is to supply the excitation dc voltage to the fixed poles of generator. OFAF oil forced. ONAF oil natural. It is important part in Synchronous Generators.

What is its uses? Stepper motor is the electrical machine which act upon input pulse applied to it. Thus it can control the output Reactive Power of the Generator. ODWF oil direct. What is an exciter and how does it work?

There are two types of exciters. OFAN oil forced. What is the function of anti-pumping in circuit breaker?

What is the difference between surge arrestor and lightning arrestor? LA is installed outside and the effect of lightning is grounded. That y always vacuum used as in HT breaker and air used as in LT. It gives the starting torque to the generator. Hence syn. Difference between a four point starter and three point starter? The shunt connection in four point starter is provided separately from the line where as in three point state it is connected with line which is the drawback in three point starter Electrical interview question: Why can't use ACB?

Actually the thing is vacuum has high arc quenching property compare to air becoz in VCB. This type of generators is used in windmills. Why syn. In simple. Give two basic speed control scheme of DC shunt motor?

By using flux control method: Generators are classified into two types 1 separately excited d. Enlist types of dc generator? What will happen when power factor is leading in distribution of power? If their is high power factor. This type of generators are used in windmills. The effect of armature flu to main flux is called armature reaction. The armature flux may support main flux or opposes main flux.

Give two basic sprrd control scheme of DC shunt motor? What is the Polarisation index value? Its ratio between insulation resistance IR i. Whenever a current carrying conductor is placed in a magnetic field it produce turning or twisting movement is called as torque.

What is the significance of vector grouping in Power Transformers? Advantages of vvvf drives over non vvvf drives for EOT cranes? What is 2 phase motor? A two phase motor is a motor with the starting winding and the running winding have a phase split. Its Single Phase induction motor which mostly squirrel cage rotor and are capacitor start capacitor run. Every power transformer has a vector group listed by its manufacturer..

Wye Secondary and the current is at 11 o clock reffered to the voltage. The armature flux may support main flux or opposes main flux Which type of A.

DYN11 means Delta primary.. Fundamentally it tells you the information about how the windings are connected delta or wye and the phase difference between the current and voltage. C motor is used in the fan ceiling fan. Its true that if birds touch the single one line phase or neutral they don't get electrical shock. Prepared By Satish Kumar.. A breaker is normally used to break a ciruit. Due to the sudden change of supply the choke will generate around volts.

At the time of seperation an air gap is formed in between the terminals. When DC supply is applied. When supply is provided the starter will interrupt the supply intermittent cycle of AC. Now there is no change of supply causes choke voltage normalized and act as minimize the current. Normally they have low resistance. Due to existing current flow the air in the gap is ionised and results in the arc. This volt will capable of to break the electrons inside the tube to make electron flow. ACSR means Aluminum conductor steel reinforced.

We can not start the Induction motor and Synchronous motors on load. Induction motor or Synchronous motor? DC Series motor has high starting torque. How tubelight circuit is connected and how it works? A choke is connected in one end of the tube light and a starter is in series with the circuit. Bulbs [devices] for AC are designed to operate such that it offers high impedance to AC supply. Once the current passes through the tube the starter circuit will be out of part.

VCB's can be used upto 11kv. What is vaccum currcuit breaker. It is used when voltage required for testing is higher than the available. The electric train is well insulated from its electrical system.

It is used with generators for charging a number of capacitor in parallel and discharging them in series.

What is encoder. We didnt feel any Shock? Unfortunately our body is a pretty good conductor of electricity. What is electric traction? What are the advantages of speed control using thyrister? An encoder is a device used to change a signal such as a bitstream or data into a code.

The code may serve any of a number of purposes such as compressing information for transmission or storage. Whenever a current carrying conductor is placed in an magnetic field it produce turning or twisting movement is called as torque. Fast Switching Characterestics than Mosfet. This is usually done by means of a programmed algorithm.

The golden rule is Current takes the lowest resistant path if you have insulation to our feet as the circuit is not complete wearing rubber footwear which doing some repairs is advisable as our footwear is a high resistance path not much current flows through our body. Low cost 3. IGBT 2. Higher Accuract. Why Human body feel Electric shock?? So if any malfunction happens the fuse connected in the particular control circuit alone will blow off.

Traction means using the electric power for traction system i. Why link is provided in neutral of an ac circuit and fuse in phase of ac circuit?

Link is provided at a Neutral common point in the circuit from which various connection are taken for the individual control circuit and so it is given in a link form to withstand high Amps.

Operation carried out in Thermal power station? The water is obtained in the boiler and the coal is burnt so that steam is obtained this steam is allowed to hit the turbine. Those values are called as pu values. To bring all the ratings into common platform we use pu concept in which. But in the case of Fuse in the Phase of AC circuit it is designed such that the fuse rating is calculated for the particular circuit i.

I t's possible by means of Electronic choke. What is "pu" in electrical engg? Pu stands for per unit and this will be used in power system single line diagram there it is like a huge electrical circuit with no of componenets generators. Otherwise it's not possible to ionise the particles in tube. The difference between the electronic and ordinary regulator is that in electronic reg. In electronic regulator triac is employed for speed cntrl.

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Electrical Engineering Interview Questions and Answers. Jump to Page.This volt will capable of to break the electrons inside the tube to make electron flow. Jeeva Raj. The armature flux may support main flux or opposes main flux. It is the voltage at which a CT gets saturated. Ex : 24 nos. If the resistance total in a series circuit doubles the current will reduce to half.

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