Mechanical Electrical Interview Questions, Mechanical And Electrical Interview Questions, Basic Electrical Interview Questions In English

A friend today we'll talk Mechanical Electrical Interview Questions, Mechanical And Electrical Interview Questions, Basic Electrical Interview Questions In English

Electrical Engineering Interview Questions


1. what's a System?

When a variety of components or parts square measure connected in an exceedingly sequence to perform a selected perform, the cluster of components that everyone represents a System


2. what's the management system?

In a System the output and inputs square measure interconnected in such a fashion that the output amount or variable is controlled by input amount, then such a system is named system.
The output amount is named a controlled variable or response and therefore the input amount is named a command signal or excitation.


3. What square measures the various sorts of management Systems?

Two major sorts of systems square measure 1) Open-loop Management System 2) control system management Systems

Open-loop systems: The Open-loop management System is one during which the Output amount has no impact on the Input amount. No feedback is a gift from the output amount to the input amount for correction.

Closed-Loop System: The Closed-loop management System is one during which the feedback is provided from the Output amount to the input amount for the correction therefore on maintain the specified output of the system.


4. what's feedback on top of things System?

The Feedback on top of things System is one during which the output is sampled and therefore the proportional signal is fed back to the input for automatic correction of the error ( any modification in desired output) for any process to induce back the specified output.


5. Why feedback is most popular within the Management System?

The role of Feedback among the system is to need the sampled output back to the input and compare the signal with the sign for error ( deviation from the desired result)
Negative Feedback leads to the higher stability of the system and rejects any disturbance signals and is a smaller amount sensitive to the parameter variations. thence on top of things systems, feedback is taken into account.


6. what's the impact of feedback on the steadiness of the system?

Positive feedback isn't used usually within the system as a result of it will increase the error signal and drives the system to instability. however positive feedbacks square measure employed in minor loop management systems to amplify sure internal signals and parameters


7. what's Latching current?

the signal Gate is to be once the thyristor starts conducting the forward current higher than the minimum price, known as Latching current, the gate signal that is applied to trigger the device is not any longer needed to stay the SCR in ON position.


8. Why thyristor is taken under consideration as Charge controlled device?

During the triggering method of the thyristor from forward blocking state to forward conductivity state through the gate signal, applying the gate signal (voltage between gate and cathode) will increase the minority carrier density within the player and thereby facilitate the reverse break over of the junction J2 and thyristor starts conducting. The higher the magnitude of the gate current pulse, the lesser is that the time needed to inject the charge and turning on the SCR. By dominant the number of charges we will manage the turning on time of the SCR.


9. What square measures the various losses that occur in thyristor whereas operating?

Different losses that occur square measure
(a) Forward conductivity losses throughout conductivity of the thyristor
(b) Loss thanks to escaping current throughout forward and reverse block.
(c) Power loss at gate OR gate triggering loss.
(d) Switching losses at stimulant and turn-off.


10. what's meant by knee purpose voltage?

Knee purpose voltage is calculated for electrical Current transformers and is an incredibly vital issue to decide on a CT. it's the voltage at that a CT gets saturated.(CT-current transformer).


11. what's a reverse power relay?

Reverse Power flow relay square measure employed in generating stations’ protection. A generating station is meant to fed power to the grid and just in case generating units square measure off, there is no generation within the plant then the plant might take power from the grid. to prevent the flow of power from the grid to the generator we have a tendency to use a reverse power relay.


12. what's going to happen if DC provide is given on the first of a transformer?

Mainly electrical device has high inductance and low resistance. In the case of DC provide there's no inductance, only resistance can act within the electric circuit. therefore high electrical current can flow through the primary facet of the electrical device. So for this reason coil and insulation can die.


13. what's the distinction between isolators and electric circuit breakers? what's the bus bar?

Isolators square measure in the main for shift purpose beneath traditional conditions however they can't operate in fault conditions. Actually, they used to analyze the CBs for maintenance. Whereas CB gets activated beneath fault conditions per the fault detected. The bus bar is nothing however a junction wherever the ability is obtaining distributed for freelance hundreds.


14. What square measure the advantage of free wheeling diode in an exceedingly Full Wave rectifier?

It reduces the harmonics and it additionally reduces sparking and curving across the mechanical switch so it reduces the voltage spike seen in an exceedingly inductive load.


15. Mention the ways for beginning an induction motor?

The different ways of beginning an induction motor:
(a) DOL: direct online starter
(b) Star delta starter
(c) Auto electrical device starter
(d) Resistance starter
(e) Series reactor starter


16. what's the ability issue of a generator at no load?

At no load Synchronous resistivity of the generator is accountable for making angle distinction. thus it ought to be zero insulation like an electrical device.


17. what's the operation of anti-pumping in circuit breaker?

When the breaker is shut at just once by a shut electric switch, the opposing pumping contactor stop shut the breaker by the shut the electric switch when if it already shut.


18. what's a stepper motor. what are its uses?

Stepper motor is that the electrical machine that bears on input pulse applied to that. it's one form of electric motor that runs in steps in either direction rather than running an incomplete cycle. so, in automation components, it's used.


19. There square measure an electrical device and an induction machine. Those 2 have an equivalent offer. that device the load current is going to be maximum? And why?

The motor has a soap load current compare to it an electrical device as a result of the motor consumes real power.. and therefore the electrical device is simply manufacturing the operating flux and its not intense. therefore the load current within the electrical device is owing to core loss thus it's minimum.


20. what's the frantic effect?

The output voltage is larger than the input voltage or receiving finish voltage is larger than the causation finish voltage.


20. what's meant by insulation voltage in cables? justify it?

It is the property of a cable by virtue of it will face up to the applied voltage while not rupturing it's referred to as the insulation level of the cable.


21. what's the distinction between MCB & MCCB, wherever it will be used?

MCB is the miniature fuse that is thermal operated and uses for brief circuit protection in a little current rating circuit. MCCB molded case fuse and is thermal operated for overload current and magnetic operation for a fast trip in brief circuit condition. undervoltage and beneath frequency could also be integral. ordinarily, it's used wherever the traditional current is over 100A.


22. wherever ought the lighting arrestor be placed in distribution lines?

Near distribution transformers and outgoing feeders of 11kv and incoming feeder of 33kv and close to power transformers in sub-stations.


23. outline IDMT relay?

It is AN inverse definite minimum time relay. In the IDMT relay, its operation is reciprocally proportional and additionally a characteristic of a minimum time when that this relay operates. It is inverse within the sense, the tripping time can decrease because the magnitude of fault current increases.


24. What square measures the electrical device losses?

TRANSFORMER LOSSES – electrical device losses have 2 sources-copper loss and magnetic loss. Copper losses square measure caused by the resistance of the wire (I2R). Magnetic losses square measure caused by eddy currents and physical phenomenon within the core. The copper loss could be a constant when the coil has been wound and so a measurable loss. physical phenomenon loss is constant for a selected voltage and current. Eddy-current loss, however, is completely different for every frequency tried and true the electrical device.


25. what's the complete kind of KVAR?

We know there square measure 3 sorts of power in Electricals as Active, apparent & reactive. thus KVAR is symbolized the “Kilo potential unit Amps with Reactive part.


26. Why temperature rise is conducted in busbars and isolators?

Bus bars and isolators square measure rated for continuous power flow, meaning they carry serious currents that raises their temperature. thus it's necessary to check this device for temperature rise.

27. what's the ability issue of a generator at no load?

At no load Synchronous resistivity of the generator is accountable for making angle distinction. thus it ought to be zero insulation like an electrical device.


28. what's the operation of anti-pumping in circuit breaker?

When the breaker is shut at just once by a shut electric switch, the opposing pumping contractor stops shutting the breaker by the shut the electric switch when if it already shut.


29. what's a stepper motor. what are its uses?

Stepper motor is that the electrical machine that bears on input pulse applied to that. it's one form of electric motor that runs in steps in either direction rather than running an incomplete cycle. so, in automation components, it's used.


30. There square measure an electrical device and an induction machine. Those 2 have an equivalent offer. that device the load current is going to be maximum? And why?

The motor has a soap load current compare to it an electrical device as a result of the motor consumes real power.. and therefore the electrical device is simply manufacturing the operating flux and its not intense.. therefore the load current within the electrical device is owing to core loss thus it's minimum.


31. what's SF6 Circuit Breaker?

SF6 is Sulpher hexa Flouride gas. if this gas is employed as arc extinction medium in an exceedingly Circuit breaker suggests that SF6 CB.


32. what's the frantic effect?

The output voltage is larger than the input voltage or receiving finish voltage is larger than the causation finish voltage.


33. what's meant by insulation voltage in cables? justify it?

It is the property of a cable by virtue of it will face up to the applied voltage while not rupturing it's referred to as the insulation level of the cable.


34. what's the distinction between MCB & MCCB, wherever it will be used?

MCB is a miniature fuse that is thermal operated and uses for brief circuit protection in a little current rating circuit. MCCB molded case fuse and is thermal operated for overload current and magnetic operation for a fast trip in brief circuit condition. undervoltage and beneath frequency could also be integral. ordinarily, it's used wherever the traditional current is over 100A.


35. wherever ought the lighting arrestor be placed in distribution lines?

Near distribution transformers and outgoing feeders of 11kv and incoming feeder of 33kv and close to power transformers in sub-stations.


36. outline IDMT relay?

It is AN inverse definite minimum time relay. In the IDMT relay, its operation is reciprocally proportional and additionally a characteristic of a minimum time when that this relay operates. It is inverse within the sense, the tripping time can decrease because the magnitude of fault current increases.


37. What square measures the electrical device losses?

TRANSFORMER LOSSES – electrical device losses have 2 sources-copper loss and magnetic loss. Copper losses square measure caused by the resistance of the wire (I2R). Magnetic losses square measure caused by eddy currents and physical phenomenon within the core. A copper loss could be a constant when the coil has been wound and so a measurable loss. physical phenomenon loss is constant for a selected voltage and current. Eddy-current loss, however, is completely different for every frequency tried and true the electrical device.


38. what's the complete kind of KVAR?

We know there square measure 3 sorts of power in Electricals as Active, apparent & reactive. thus KVAR is symbolized the “Kilo potential unit Amps with Reactive part.


39. 2 bulbs of 100w and 40w severally connected serial across a 230v offer that bulb can glow bright and why?

Since 2 bulbs square measure serial they'll get an equal quantity of electrical current however because the offer voltage is constant across the bulb (P=V^2/R). So the resistance of the 40W bulb is larger and the voltage across 40W is additional (V=IR) thus 40W bulb can glow brighter.


40. Why temperature increase in operated by bus bars and isolators?

Bus bars and isolators square measure rated for continuous power flow, meaning they carry serious currents that raises their temperature. thus it's necessary to check these devices for temperature rise.


41. what's the distinction between synchronous generator & asynchronous generator?

In simple, an asynchronous generator supplies each active and reactive power however asynchronous generator(induction generator) supply’s solely active power and observes reactive power for magnetizing. This type of generator square measure employed in windmills.


42. what's an Automatic Voltage regulator(AVR)?

AVR is an Associate in Nursing abbreviation for Automatic transformer. It is necessary half in Synchronous Generators, it controls the output voltage of the generator by dominant its excitation current. so it will manage the output Reactive Power of the Generator.


43. the distinction between a four-purpose starter and a 3 purpose starter?

The shunt association in four purpose stater is provided on an individual basis kind the road wherever as in 3 purpose stater it's connected with a line that is that the disadvantage in 3 purpose stater


44. Why the capacitors work on ac only?

Generally, the condenser offers infinite resistance to dc components(i.e., block the dc components). it permits the ac elements to undergo.


45. what percentage styles of colling system it transformers?

1. ONAN (oil natural, air natural)
2. ONAF (oil natural, air forced)
3. OFAF (oil forced, air forced)
4. ODWF (oil direct, water forced)
5. OFAN (oil forced, air forced)


46. Operation disbursed in Thermal power stations?

The water is obtained within the boiler and therefore the coal is burnt in order that steam is obtained this steam is allowed to hit the rotary engine, the rotary engine that is not to mention the generator generates the electricity.


47. what's a two-part motor?

A 2 part motor may be a motor with the beginning winding and therefore the running winding has a part split. e.g;ac servo motor. where the auxiliary winding and therefore the management winding have a part split of ninety degrees.


48. what's the principle of motor?

Whenever a current-carrying conductor is placed in Associate in Nursing magnetic flux it turns out turning or twisting movement is named as a force.


49. what's meant by coil reaction?

The result of coil contagious disease to main flux is named coil reaction. The coil flux could support the main flux or opposes the main flux.


50. what's the distinction between synchronous generator & asynchronous generator?

In simple, an asynchronous generator supplies each active and reactive power however asynchronous generator(induction generator) supply’s solely active power and observes reactive power for magnetizing. This type of generator square measure employed in windmills.


51. What is MARX Circuit?

It is used with generators for charging a variety of condensers in parallel and discharging them serially. It is used once the voltage needed for testing is more than the on the market.


52. What square measure the benefits of speed management exploitation thyristor?

Advantages :

1. quick switch Characteristics than Mosfet, BJT, IGBT
2. Low cost
3. Higher correct.


53. what's ACSR cable and wherever we tend to use it?

ACSR means that aluminum conductor steel bolstered, this conductor is employed in transmission & distribution.


54. What's the one main distinction between UPS & electrical converter? And engineering science & natural philosophy engineering?

Uninterrupted power offer is especially used for a brief time. means that consistent with ups VA offers backup. 

ups are additionally 2 varieties: online and offline. 

on-line ups having high V and amp for a very long time backup with high dc voltage. but ups begin with 12v dc with seven amp. however electrical converter is start with 12v,24, dc to 36v dc and 120amp to 180amp battery with a very long time backup.


55. what's going to happen once the power issue is leading to the distribution of power?

If there is a high power issue, i.e if the facility issue is about to one:

(a) Losses in kind of heat are going to be reduced,
(b) Cable becomes less large and straightforward to hold, and extremely low-cost to afford, &
(c) It conjointly reduces overheating of transformers.


56. What square measure the benefits of a star-delta starter with an induction motor?

(1). the most advantage of exploiting the star delta starter is a reduction of current throughout the beginning of the motor. Starting current is reduced to 3-4 times Of current of Direct online beginning. 

(2). therefore the beginning current is reduced, the voltage drops throughout the beginning of the motor in systems square measure reduced.


57. Why Delta-Star Transformers class measurements used for Lighting Loads?

For lighting masses, a neutral conductor is should and therefore the secondary should be star winding. and this lighting load is often unbalanced all told 3 phases. to reduce the present unbalance within the primary we tend to use delta winding within the primary. therefore delta/star electrical device is employed for lighting masses.


58. Why pc buzzing sound occurred in the HT transmission line?

This computer noisy sound is returning because of ionization (breakdown of air into charged particles) of air around the transmission conductor. This result is named Corona result, and it's thought-about as power loss.


59. what's rated speed?

At the time of motor taking traditional current (rated current), the speed of the motor is named rated speed. it's a speed at that any system takes little current and provides most potency.


60. one tube light is connected between the Two-lines it'll the tube light are glow or not?

If the voltage between the 2 parts is capable of the lamp voltage then the lamp can glow. once the voltage distinction is massive it can it'll injury the lamp and once the distinction is smaller the lamp will glow looking on the sort of lamp.


61. What square measures the various operation regions of the SCR?

SCR or thyristor can have 3 regions of operations supported by the mode during which the device is connected within the circuit.

Reverse obstruction region: once the cathode of the thyristor is formed positive with relation to the anode and no gate signal is applied. during this region, SCR exhibits the reverse obstruction characteristics like a diode.

Forward obstruction region: during this region the anode of the thyristor is formed positive with relation to the cathode and no gate signal is applied to the thyristor. a little discharge current flow during this mode of operation of the thyristor

Forward conductivity region: once the forward voltage applied between the anode and cathode will increase at a specific break over voltage avalanche breakdown takes place and thyristor starts conducting current in forwarding direction. By this sort of triggering the device damages the SCR.


62. What is Holding current?

When SCR is conducting current in forwarding conductivity state, SCR can come back to forward obstruction state once the anode current or forward current falls below a coffee level known as Holding current

Note: Latching current and Holding current don't seem to be the same. Latching current is related to the activate method of the SCR whereas holding current is related to the put-off method. normally holding current are slightly lesser than the latching current.


 63. Why thyristor is taken into consideration as Charge controlled device?

During the triggering method of the thyristor from forwarding obstruction state to forward conductivity state through the gate signal, applying the gate signal (voltage between gate and cathode) will increase the minority carrier density within the player and thereby facilitate the reverse break over

of the junction, J2 and thyristor start conducting. The higher the magnitude of the gate current pulse, the lesser is that the less time needed to inject the charge and turning on the SCR. By dominant the quantity of charge, we are able to management the turning on time of the SCR.

64. What square measures the various losses that occur in thyristor whereas operating?

Different losses that occur square measure
Forward conductivity losses throughout conductivity of the thyristor
Lose thanks to discharging current throughout forward and reverse obstruction.
Power loss at gate triggering loss.
Switching losses at stimulation and turn-off.



65. What square measures the benefits of speed management mistreatment thyristor?
Advantages :

1. quick shift Characteristics than MOSFET, BJT, IGBT
2. Low cost 3. Higher correct.


66. What happens if I connect an electrical device to a generator load?

Connecting an electrical device across a generator continually improves power-factor, however, it'll facilitate depends informed the engine capacity of the generator, different wise the generator is overloaded thanks to the additional watts consumed thanks to the development on pf. Secondly, don’t connect an electrical device across an Associate in Nursing generator whereas it's finding out or with no different load.


67. Why the capacitors work on ac only?

Generally, an electrical device offers infinite resistance to dc elements (i.e., block the dc components). it permits the ac elements to submit to.


68. Explain the operating principle of the circuit breaker?

A circuit Breaker is one that makes a circuit. breaks its 2 contacts specifically fastened contact & moving contact below traditional conditions the moving contact comes in-tuned with fastened contact thereby forming the closed contact for the flow of current. 

throughout abnormal & faulty conditions when current exceeds the rated value Associate in Nursing arc is created between the fastened & moving contacts & thereby it forms the circuit Arc is destroyed by the Arc extinguishing media like air, oil, vacuum, etc.


69. What is the distinction between earth resistance and earth conductor resistance?

Only one of the terminals is clear within the earth's resistance. so as to seek out the second terminal we must always recourse to its definition: Earth Resistance is that the resistance existing between the electrically accessible part of a buried conductor and another purpose of the world, that is much away.

The resistance of the conductor has the subsequent components:

(A) the resistance of the metal which of the affiliation thereto.
(B) the contact resistance of the encompassing earth to the conductor.


70. What is the use of opposition relay in ht voltage?

A lock-out relay is powered by an equivalent electrical supply because of the management power and is operated by a key lock switch. The relay itself might have up to twenty-four contact points at intervals in the unit itself. this permits the management power for multiple machines to be barred out by the flip of one key switch.


71. What is the ability issue of an associate degree generator at no load?

At no load Synchronous electric resistance of the generator is answerable for making angle distinction. thus it ought to be zero insulants like inductance.


72. How to confirm electrical condenser tolerance codes?

In electronic circuits, the electrical condenser tolerance is determined by a code that seems on the casing. The code may be a letter that usually follows a three-digit range (such as 130Z). The first 2 are the first and ordinal important digits and also the third may be a multiplier factor code. Most of the time the last digit tells you ways several zeros to put in writing once the primary 2 digits and these are scans as Pico-Farads.


73. Why are most analog o/p devices having o/p vary four to twenty mA and not zero to twenty mA?

4-20 mA may be a normal vary wont to indicate measured values for any method. the explanation that 4ma is chosen rather than zero mA is for fail-safe operation. For example- a pressure instrument provides output 4mA to point zero psi, up to twenty mA to point a hundred psi or full scale. because of any drawback in the instrument 

(i.e) a broken wire, its output reduces to zero mA. thus if the vary is zero-20 mA then we will differentiate whether or not it's because of a broken wire or because of 0 psi.


74. What is meant by knee purpose voltage?

Knee purpose voltage is calculated for electrical Current transformers and is an incredibly necessary issue to decide on a CT. it's the voltage at that a CT gets saturated.(CT-current transformer).

75. what is the complete variety of KVAR?

We know there are 3 varieties of power in Electrical as Active, apparent & reactive. thus KVAR represents the “Kilo V Amps with Reactive part.


76. what is the principle of motor?

Whenever a current-carrying conductor is placed in an associate degree force field it turns out turning or twisting movement is termed as a force.


77. Types of dc generators?

DC Generators are classified into 2 sorts 1)separately excited DC generator
(2) self-excited DC generator, which is more classified into

(1) series 

(2) shunt and 

(3) compound(which is more classified into additive and differential).


78. Which motor has the high beginning force and Staring current DC motor, Induction motor, or Synchronous motor?

DC Series motor has high beginning force. we will not begin the Induction motor and Synchronous motors on load, however can't begin the DC series motor while not load.


79. Define stepper motor. what's the employment of stepper motor?

The motor that works or acts on the applied input pulse in it, is termed a stepper motor. This stepper motor is below the class of electric motor, which regularly doesn't totally rely on a complete cycle. It likes to works in either direction associated with steps. for this purpose, it principally employed in automation components.



80. What is a pair of the part motor?

A 2 part motor may be a motor with the beginning winding and also the running winding has a part split. e.g;ac servo motor. where the auxiliary winding and also the management winding have a part split of ninety degrees.



81. Which type of A.C motor is employed within the fan (ceiling fan, fan, pedestal fan, bracket fan, etc) that are noticed within the homes?

Its Single part induction motor that principally coop rotor and ar electrical condenser begin electrical condenser run.



82. Give 2 basic speed management themes of DC shunt motor?

1. By mistreatment flux management technique: in this method, a resistor is connected across the sector winding to manage the sector currently. so by the dynamic presence, the flux created by the sector winding is modified, and since speed is reciprocally proportional to flux speed is controlled

2.armature management technique in this method a resistor is connected across coil winding by varied the resistance the worth of resistive drop(Iara) is varied, and since speed is directly proportional to Eb-IaRathe speed is controlled.



83. Difference between a four-purpose starter and 3 purpose starter?

The shunt association in four purpose starters is provided one by one kind the road wherever as in 3 purpose starters it's connected with a line that is that the downside in 3 purpose starters.



84. What is the distinction between synchronous generator & asynchronous generator?

In simple, an asynchronous generator supplies each active and reactive power however asynchronous generator(induction generator) supply’s solely active power and observes reactive power for magnetizing. this sort of generator ar employed in windmills.


85. Why syn. generators are used for the assembly of electricity?

Synchronous machines have the capability to figure on completely different|completely different} power issue (or say different imagined power varied the sector voltage. Hence syn. generators r used for the assembly of electricity.


86. Why is that the beginning current high during a DC motor?

In DC motors, Voltage equation is V=Eb-Iara (V = Terminal voltage, Eb = Back voltage in Motor, IA = coil current,Ra = Armature resistance). In the beginning, Eb is zero. Therefore, V=IaRa, Ia = V/Ra, where Ra is incredibly less like zero.01ohm.i.e, IA can become staggeringly magnified.


87. What are the benefits of a star-delta starter with an induction motor?

The main advantage of mistreatment of the star delta starter is a reduction of current throughout the beginning of the motor. beginning current is reduced to 3-4 times Of current of Direct online beginning. 

(2). therefore the beginning current is reduced, the voltage drops throughout the beginning of the motor in systems are reduced.


88. Why DC series motor cannot be commenced on no-load?

Series motor can not be started while not load owing to high beginning force. Series motor is employed in Trains, Crane, etc.


89. Mention the ways for beginning associate degree induction motor?

The different ways of beginning associate degree induction motor
DOL: direct online starter
Star delta starter
Auto electrical device starter
Resistance starter
Series reactor starter


90. What are Motor Generator Sets and make a case for the various ways in which the motor-generator set is used?

Motor Generator Sets are a mix of associate degree electrical generator associate degreed an engine mounted along to create one piece of kit. The motor-generator set is additionally named as a Genset, or additional unremarkably, a generator The motor-generator set will employ in the subsequent totally different ways:

1.Alternating current (AC) to electricity (DC)
2.DC to AC
3.DC voltage to DC at another voltage
4.AC frequency to AC at another harmonically-related frequency



91. Which type of motor is employed in trains, what's the rating of offer used to make a case for operating principal?

The Dc series is within the trains to induce high beginning force whereas at the beginning of the trains and in operation, the voltage is 1500v dc.

92. What is a reverse power relay?

Reverse Power flow relays are employed in generating station protection. A generating station is meant to fed power to the grid and just in case generating units are off, there is no generation within the plant then the plant might take power from the grid. to prevent the flow of power from the grid to the generator we tend to use a reverse power relay.

93. What is the appliance of DC Motors in the Thermal Power Plant?

In thermal power stations, dc motors are used surely management and significant emergency operations that are equipped with dedicated batteries. DC motors operate as backup drives for traditional ac drive systems once ac power offer to the plant is lost.
In a thermal power plant, the dc motors find applications for activity management functions like


Turbine governor motor
Governor limit setting
Motor operated rheostats
Emergency lubrication for the turbines main, boiler, feed pumps,
Generator H2 oil seal
DC motor operated valves

DC motors used in thermal plants are classified into two 2 sorts supported by the kind of application.

DC motors finishing up control operation
Dc motors finishing up Emergency perform

Control functions: This class consists of the rotary engine governor motor, governor limiting setting, motor-operated rheostats, etc. These motors are tiny, concerning 1/8 power unit or less. they're operated quite occasionally for a brief length.

Emergency functions: This class consists of turbine-generator emergency (lubrication) bearing oil pumps and emergency animal oil pumps. Such pumps may be provided for turbine drives of feedwater pumps, fans, and alternative giant hundreds. the dearth of lubrication throughout a closure while not ac power can ruin the linings of the bearings and injury the shaft.

Hydrogen animal oil pump is provided to forestall the escaping of element (for giant turbine-generators element cooling is provided for economical cooling) from the casing by providing a decent seal with air mass oil


94. What are the Advantages & Disadvantages of Synchronous motors?

Advantage or Merits:

One of the key advantages of victimization electric motor is that the ability to regulate the facility issue. AN frenzied electric motor will have a leading power issue and may be operated in parallel to induction motors and different insulation power issue hundreds thereby rising the system power issue.

In an electric motor, the speed remains constant no matter the masses. This characteristic helps in industrial drives wherever constant speed is needed no matter the load it's driving. It additionally helpful once the motor is needed to drive another generator to provide at a unique frequency as in frequency changes.

Synchronous motors are often made with wider air gaps than induction motors that make these motors automatically a lot of stables.

In synchronous motors, electro-magnetic power varies linearly with the voltage.
Synchronous motors sometimes operate with higher efficiencies ( quite 90%) particularly in low speed and unity power issue applications compared to induction motors

Disadvantages or Demerits:

Synchronous motors need dc excitation that should be equipped from external sources.
Synchronous motors area unit inherently not self beginning motors and desires some arrangement for its beginning and synchronizing.

The cost per kilowatt output is mostly over that of induction motors.
These motors can not be used for variable speed applications as there's no chance of speed adjustment unless the incoming provide frequency is adjusted (Variable Frequency Drives).
Synchronous motors can not be started on load. Its beginning torsion is zero.
These motors have a tendency to hunt.

When loading on the electric motor will increase on the far side its capability, the synchroneity between the rotor and mechanical device rotating force field is lost and motor involves a halt.

Collector rings and brushes area unit needed leading to increase in maintenance.
Synchronous motors can not be helpful for applications requiring frequent beginning or high beginning torques needed.

Mechanical Engineering Interview Questions

1. justify the second law of physics.

The entropy of the universe will increase over time and moves towards the most price.


2. What varieties of pipes area unit used for steam lines?

Normally galvanized pipes aren't used for steam. a low-carbon steel with screwed or welded fittings area unit the norm. Pressure and temperature area unit vital factors to be thought-about in what sort of materials to be used. Steam even at low pressures is often very dangerous.


3. what is the difference between the shear center & flexural center of the twist and elastic center?

The shear center is that the center of mass of a cross-sectional. The flexural center is that the center of twist, that is that the purpose of a beam that you simply will add a load while not torsion. The elastic center is found in the middle of gravity. If the item is homogenized and symmetrical in each direction of the cross-sectional then they're all equivalent.


4. what's ferrite?

Magnetic iron rock


5. what's the distinction between projectile motion and rocket motion?

A projectile has no motor/rocket on that, therefore all of its momenta is given to that because it is launched. AN example of a projectile would be the pen that you simply throw across space.

A rocket or missile will have a motor/rocket on that therefore it will accelerate itself whereas moving then resist different forces like gravity.


6. what's a cotter joint?

These sorts of joints area unit wont to connect 2 rods, that area unit underneath compressive or tensile stress. The ends of the area of the rod unit within the manner of a socket and shaft that work along and therefore the cotter is driven into a slot that's common to each item drawing them tightly along. The lastingness of the steel is proportionate to the strength required to offset the strain on the fabric divided by the number of joints utilized.


7. what's the alloy of tin and lead?

A tin and lead alloy is usually referred to as solder. sometimes solder could be a wire with a rosin core used for bonding.


8. What will F.O.F. signify in piping design?

FOF stands for Face of the rim. A rim has either of the 2 sorts of faces:

(a) Raised face
(b) Flat face

The F.O.F is employed to grasp the correct dimension of the rim so as to avoid the minute errors in measuring just in case of vertical or horizontal pipelines.


9. justify Otto cycle.

The Otto cycle is often explained by a pressure-volume relationship diagram. It shows the functioning cycle of a 4 stroke engine. The cycle starts with an intake stroke, closing the intake and moving to the compression stroke, beginning of combustion, power stroke, heat exchange stroke wherever heat is rejected, and therefore the exhaust stroke. it absolutely was designed by Nicolas Otto, a German engineer.


10. what's the gear ratio?

It is the magnitude relation of the number of revolutions of the pinion gear to at least one revolution of the do-nothing gear.


11. what's annealing?

It is a method of heating a fabric higher than the recrystallization temperature and cooling once a selected amount. This will increase the hardness and strength of the fabric.


12. what's ductile-brittle transition temperature?

It is at the temperature below that the tendency of a fabric to fracture will increase instead of forming. Below this temperature, the fabric loses its malleability. it's additionally referred to as zilch malleability Temperature.


13. what's a uniformly distributed load?

A UDL or uniformly distributed load could be a load, that adjoins a beam in much the way that every unit length is loaded to an equivalent extent.


14. What area unit the variations between mechanics and hydraulics?

(a) operating fluid: mechanics use air, fluid mechanics use Oil
(b) Power: gas power but hydraulic power
(c) Size: P elements area unit smaller than H elements
(d) Leakage: Leaks in fluid mechanics cause fluid to be projected around the elements. In mechanics, the air is leaked into the atmosphere.
(e) mechanics acquire power from AN compressor whereas fluid mechanics need a pump
(f) Air is compressible, hydraulic oil isn't


15. what's enthalpy?

Enthalpy is that the physical property of a chemical system.


16. what's a positive displacement pump?

A positive displacement pump causes a liquid or gas to maneuver by tack a set quantity of fluid or gas so forcing (displacing) that cornered volume into the piping. Positive displacement pumps are often additionally classified as either rotary-type (for example the rotary vane) or lobe pumps kind of like oil pumps utilized in automobile engines. These pumps provide a non-pulsating output or displacement in contrast to the mutual pumps. Hence, they're referred to as positive displacement pumps.


17. Why would you employ fluid mechanics instead of pneumatics?

Hydraulics is appropriate for higher forces and precise motion than mechanics. this can be as a result of hydraulic systems usually run at considerably higher pressures than mechanics systems. The movements area unit a lot of precise (repeatable) as a result of fluid mechanics uses an incompressible liquid to transfer power while mechanics use gases.
Pneumatic systems have some blessings too. they're sometimes considerably cheaper than hydraulic systems, will move quicker (gas a lot less viscous than oil), and don't leak oil if they develop a leak.


18. what's isometric drawing?

It is a three-D drawing utilized by draftsmen, architects, etc


19. What area unit the benefits of drugs drive?

In general, a gear drive is helpful for power transmission between 2 shafts, that area unit almost about one another (at most at 1m distance). additionally, it's most potency whereas sending power. it's sturdy compare to different like belts chain drives etc. you'll be able to modification the facility to hurry magnitude relation.

Advantages: –
It is wont to get numerous speeds in numerous load conditions.
It will increase fuel potency.
Increases engine potency.
Need less power input once operated manually.


20. that conducts heat faster steel copper and brass?

Copper conducts heat quicker than steel or brass. Any material that's sensible for conducting heat is additionally sensible for electricity in most cases. Wood terrible for transferring heat therefore is additionally a nonconductor for electrical.


21. however, pipe flanges area unit electrically insulated?

Pipe flanges area unit shielded from corrosion by suggests that of electrolysis, with stuff flanges. The piping system is electrically insulated by what's referred to as a killing anode. A bag of promptly corrodible metal is buried within the ground with a wire running from the pipe to the bag so the killing anode can corrode initially. If any electrical current charges the pipe, it additionally is a ground.


22. what's a method Flow Diagram?

A method flowchart (or System Flow Diagram) shows the relationships between the key elements within the system. It additionally has basic data regarding the fabric balance for the method.


23. wherever the gas system is used?

Any system that wants redundancy in work wants mechanics, as a result of the mechanical device of the gas system has periodical operations (intermittent work, not as the hydraulic pump). The compressed gas may well be accumulated in tanks with high pressures and used even though the mechanical device unsuccessful.


24. Why gas containers area unit largely cylindrical in shape?

The most economical form for withstanding high could be a sphere however that might be expensive to manufacture. A cylinder with a rounded prime and a rounded bottom (look beneath, the flat base is really welded around the outside, the lowest of the gas instrumentation is really domed) could be a less expensive form to manufacture while still having sensible strength to resist the inner pressure level.


25. however, is the primary solid solution structure shaped in steel?

Martensite transformation begins once-solid solution is cooled below a particular important temperature, referred to as the martensite begins temperature. As we have a tendency to go below the primary solid solution begin temperature, a lot of and a lot of primary solid solution forms and complete transformation happens solely at a temperature referred to as martensite end temperature. Formation of primary solid solution needs that the solid solution part should be cooled chop-chop.


26. what's an orthographic drawing?

Orthographic projections area unit views of a 3D object, showing three faces of it. the three drawings area unit aligned so if the page were rolled, it'd produce a part of the form. it's additionally referred to as multiview projections.
The 3 faces of AN object comprise its arrange read, front read, and vista. There area unit a pair of sorts of writing projection, that area unit first angle projection and third angle projection.


27. what's representative elementary volume?

The smallest volume over that measurement is often created which will yield a representative of the total.


28. Why area unit LNG pipes curved?

LNG pipes area unit incurved as a result of LNG is condensed gas (-164 deg cel) therefore it will expand the pipes that's what engineers designed the LNG pipes area unit curve kind.


29. What will momentum mean?

Angular momentum is AN expression of AN object's mass and move speed.
Momentum is that the speed of AN object that times its mass, or how briskly one thing is moving what quantity it weighs. Therefore, momentum is that the object's mass times the angular speed wherever angular speed is how briskly one thing is rotating expressed in terms like revolutions per minute or radians per second or degrees per second.


30. are you able to use petrol in a very hydraulic system?

Hydraulic fluid needs to pass a unique set of standards than petrol. petrol has tackifiers, lower sulfur content, and different ingredients that might prove harmful to the seals and different elements in a very mechanism. If it's AN emergency solely do you have to hump?


31. What causes white smoke in locomotive engines?

That is the engine running too lean lack of fuel, This condition can cause warming and failure of the engine.


32. what's the role of chemical elements in welding?

Nitrogen is employed to stop consistency within the attachment member by preventing gas and air from getting into the liquified metal throughout the attachment method. different gases are used for this purpose like atomic number 18, Helium, greenhouse gas, and therefore the gases are given off once the flux burns away throughout SMAW (stick) attachment.


33. What will an inexperienced field project mean?

Greenfield comes ar those come, that doesn't produce any environmental nuisance (pollution), follows environmental management system and EIA (environment impact assessment). These come ar sometimes of huge magnitude.


34. What Is the strain & produces strain and produces stress?

A Force applied to an associate degree object can cause a displacement. Strain is effectively a life of this displacement change long divided by original length,
Stress is that the Force applied divided by the realm it's applied. Example. pounds per sq. inch
Therefore, to answer the question, the applied force produces each, and Strain Stress and Strain are connected along by varied material properties like Poisson’s quantitative relation and Young’s Modulus.


35. however, will ore grow to be steel?

To make Steel, the ore is refined into iron and every one of the carbon is burned away victimization terribly high heat (Bessemer). A proportion of Carbon (and different trace elements) ar additional back to form steel. 

36. what's knurling?

Knurling may be a machining method commonly carried out on a center shaper. The act of Knurling creates a raised criss-cross pattern on a swish spherical bar that might be used as a handle or one thing that needs further grip.


37. what's the ratio of a double pulley?

It solely takes 0.5 the trouble to maneuver associate degree object however doubly spaced.


38. what's extruded aluminum?

Extrusion is that the method wherever a metal or an ingot is forced through an arbor to elongate it and/or provides it a final form.
Extruded atomic number 13 may be a common kind of creating tiny atomic number 13 wire, bars or beams and lots of styles of tiny non-structural, ornamental items.


39. What are the points within the stress-strain curve for steel?

Proportional limit, elastic limit or yield purpose, final stress, and stress at failure.