Electrician 3rd Semester - Module 1 : DC Generator

Questions: Level 1 5 What is the formula to calculate back emf of a D.C motor? 1 What is the name of the part marked ‘X’ in V A Eb = Volts DC generator? IaRa

B Eb = V x Ia Ra Volts

C Eb = V – Ia Ra Volts

D Eb = V + Ia Ra Volts 6 What is the name of the part marked ‘X’ in DCgenerator?

A Armature core B Armature core C Commutator raiser D Commutator segment 2 What is the name of D.C generator? A Pole tip B Pole coil C Pole core D Pole shoe 7 What is the name of the D.C generator? A Differential long shunt compound B Differential short shunt compound C Cumulative long shunt compound D Cumulative short shunt compound 3 Which rule is used to find the direction of induced emf in D.C generator? A Cork screw rule A Shunt generator B Right hand palm rule B Series generator C Fleming’s left hand rule C Compound generator D Fleming’s right hand rule D Separately excited generator 4 Which formula is used to calculate the 8 Which energy is converted into electrical generated emf in D.C generator? energy by generator? φZN A Heat A Generated emf = Volt 60 B Kinetic φZN A C Chemical B Generated emf = x Volt 60 P D Mechanical φZN P 9 What is the name of D.C generator? C Generated emf = x Volt 60 A ZN P D Generated emf = x Volt 60 X φ A

A Short shunt compound generator

B Long shunt compound generator

C Differential compound generator

D Cumulative compound generator

- NIMI Question Bank - Page1/ 7 10 What is the principle of D.C generator? 14 How many parallel paths in duplex lap A Cork screw rule winding of a 4 pole DC generator? B Fleming’s left hand rule A 4 C Fleming’s right hand rule B 6 D Faradays laws of electromagnetic induction C 8 11 What is the formula for dynamically induced D 12 emf ? 15 Name the part of DC generator? A BLV volts B BL sinθ volts C BLV sinθ volts D BLV cosθ volts 12 Which rule is used to find direction of magnetic field ?

A Cork screw rule A Side end plates B Right hand palm rule B Pole shoe lamination C Fleming’s left hand rule C Commutator segment D Fleming’s right hand rule D Armature core lamination 13 What is the name of the part of DC generator?

A Stator B Pole core C Pole shoes D Yoke (or) frame

- NIMI Question Bank - Page2/ 7 Questions: Level 2 6 Why the armature core of a DC generator is laminated? 1 How interpoles are connected in a DC A Reduce the copper loss generator? B Reduce the friction loss A In series with armature C Reduce the hysteresis loss B In parallel with armature D Reduce the eddy current loss C In series with shunt field 7 Why armature resistance of a D.C generator D In parallel with shunt field is very low? 2 What is the necessity of residual magnetism A Reduce armature current in a self excited DC generator? B Reduce armature voltage drop A Build up the voltage C Run armature with less weight B Reduce the field current D Reduce the temperature of armature C Reduce armature current 8 Why the D.C generator should run in D Maintain constant output voltage clockwise direction only? 3 Which are the two points that the brush A Protect brushes from damage contact resistance measured in D.C B Protect the residual magnetism machines? C Avoid short circuit in armature A Resistance between the opposite brushes D Avoid over loading of generator B Resistance between brush and 9 Why compensating winding is provided in commutator raiser large DC generators? C Resistance between brush and A Connect more loads commutator B Reduce commutation effect D Resistance between brush and armature C Neutralize armature reaction effect conductors D Increase the efficiency of generator 4 Which voltage drop is indicated in the portion 10 What is the reason for DC generator fails to marked as ‘X’? build up voltage? A Loose brush contract B Armature resistance is more C Field resistance is above critical resistance D Prime mover is running at above rated speed 11 What is the name of generator, if its field is connected in parallel with armature? A Shunt generator B Series generator C Compound generator A Full load voltage drop D Self excited generator B Armature voltage drop 12 What is the purpose of pole shoe in DC C Armature reaction drop generator? D Shunt field voltage drop A Reduce the air gap 5 What is the name of the compound B Increase the field strength generator, if the shunt field is connected in C Minimize the magnetic losses parallel with armature? D Spread out flux uniformly in the air gap A Long shunt compound 13 What is the function of split rings in DC B Cumulative compound generator? C Differential compound A Maintain constant voltage D Short shunt compound B Collects the current unidirectionally

C Reduces the voltage drop at brushes

D Increases the terminal voltage than rated

- NIMI Question Bank - Page3/ 7 14 Which material is used to make brush in 21 Which type of D.C generator is used for arc generator? welding? A Steel and graphite A Shunt generator B Carbon and graphite B Series generator C Cast iron and graphite C Differential compound generator D Aluminium and graphite D Cumulative compound generator 15 Why DC generators are loosing their residual 22 What is the property of wave winding in D.C magnetism? generator? A Heavy short circuit in load A Low current low voltage B Running without load continuous B High current low voltage C Continuous running without break C Low current high voltage D Change of direction of rotation very often D High Current high voltage 16 How does the magnetic circuit complete 23 What is the purpose of resistance wire used through the yoke and poles in a generator? in the commutator connection in D.C A Field coils generator? B Armature core C Laminated pole core D Winding conductors in armature 17 Why the terminal voltage decreases if load increases in DC shunt generator? A Because of armature reaction effect A Maintain constant voltage B Due to increased in armature resistance B Nullifying statically induced emf C Because of brush voltage drop decreases C Increasing statically induced emf D Due to increased in shunt field inductance D Smooth reversal of current direction 18 Which type of DC generator is used for long 24 Why solid pole shoes are used in D.C distance distribution lines? generator? A Shunt generator A To reduce the copper loss B Series generator B To increase the residual magnetism C Differential compound generator C To decrease the residual magnetism D Cumulative compound generator D To reduce the reluctance of magnetic path 19 Which method is used to improve the 25 Which metal is used to make large capacity insulation resistance in DC generator? DC generator yoke? A Replacing the brushes frequently A Cast iron B Heating the machine by running periodically B Soft iron C Cleaning the commutator segments regularly C Aluminium D Blowing hot air in to the machine during D Rolled Steel maintenance 26 What is the function of split rings in a D.C 20 Which type of D.C Generator works in generator? absence of residual magnetism? A Supplies output continuously A Shunt generator B Makes output in the uni direction B Series generator C Makes output in the opposite direction C Compound generator D Collects the output from alternate conductors D Separately excited generator 27 Which type of voltage is induced dynamically in a D.C generator? A Pulsating voltage B Oscillating voltage C Alternating voltage D Direct current voltage

- NIMI Question Bank - Page4/ 7 28 What is the purpose of slot marked as ‘X’? 31 Why the pole core stampings are laminated in DC generator? A Reduce the friction loss B Reduce the windage loss C Reduce the hysteresis loss X D Reduce the eddy current loss 32 Which type of DC generator is used for A To fix the key way electroplating process? B To make air circulation A Shunt generator C For lubrication purpose B Series generator D For easy removal from shaft C Differential compound generator 29 What is the purpose of field coils in D.C D Cumulative compound generator generator? 33 What is the purpose of compensating winding A To increase the flux in air gap in DC generator? B To decrease the magnetizing current A Minimizes rough commutation C To magnetize the poles to produce coil flux B Maintain constant output voltage D To increase the reluctance of magnetic path C Neutralizes the demagnetizing effect 30 Which metal is used to make pole core of D Decreases the excitation current of field coils large DC generator machines? A Soft iron B Cast iron C Cast steel D Stainless steel

- NIMI Question Bank - Page5/ 7 Questions: Level 3 5 What is the effect in D.C generator, if it is kept ideal for long time? 1 What is the effect if the shunt field resistance A Field coil resistance increases is above critical resistance value in a B Armature resistance increases D.C generator? C Increase the armature reaction A Output voltage is pulsating D Looses its residual magnetism B Output voltage is above normal 6 Calculate the induced emf of 4 pole dynamo C Generator fails to build up voltage having 1000 rpm lap wound and total D Generator builds up voltage normally number of conductors is 600, the flux / pole 2 What is the effect of armature reaction in DC is 0.064 wb? generator? A 160V A Output voltage increases B 320V B Output voltage decreases C 480V C Output voltage is pulsating D 640V D Output voltage will become zero 7 What is the effect on induced emf if the main 3 Calculate the emf genarated in a 4 pole DC field flux get distorted in DC generator? generator with simplex wave wound A Induced EMF increases armature has 1020 conductors and driven at B Induced EMF decreases a speed of 1500 rpm, the flux / pole is 0.007 C No change in induced EMF webers? D Induced EMF becomes zero A 178 V 8 What is the cause for heavy sparking in B 243 V brushes of DC generator? C 357 V A Shunt circuit in field winding D 428 V B Short circuit in armature winding 4 How the effect of armature reaction can be C MNA and GNA position changed neutralized in large DC generators? D Too much spring tension as brush A Using compensating winding B Providing additional inter poles C Increasing brush contact resistance D Adding resistance wires with winding

- NIMI Question Bank - Page6/ 7

Module 1: DC Generator - Key paper

Questions: Level 1 Questions: Level 2 Questions: Level 3

SL.No Key SL.No Key SL.No Key 1 C 1 A 1 C 2 A 2 A 2 B 3 D 3 C 3 C 4 C 4 C 4 A 5 C 5 D 5 D 6 D 6 D 6 D 7 D 7 B 7 B 8 D 8 B 8 C 9 D 9 C 10 D 10 C 11 C 11 A 12 D 12 D 13 A 13 A 14 C 14 B 15 D 15 D 16 B 17 A 18 D 19 D 20 D 21 C 22 C 23 D 24 D 25 D 26 B 27 C 28 A 29 C 30 C 31 D 32 A 33 C

- NIMI Question Bank - Page7/ 7 Electrician - 3rd Semester - Module 2 : DC Motor

Questions: Level 1 6 How many parallel paths in duplex lap winding in the armature of 4 pole D.C Motor? 1 Which instrument is used to measure A 2 armature winding resistance? B 4 A Megger C 6 B Multimeter D 8 C Series type Ohm meter 7 Which rule determines the direction of D Kelvin bridge rotation of armature in D.C motor? 2 Which instrument is used to test armature A Right hand grip rule winding for short and open circuit? B Right hand palm rule A Tong Tester C Fleming’s left hand rule B Internal Growler D Fleming’s right hand rule C External Growler 8 What is the name of D.C motor? D Digital multimeter 3 What is the name of the speed control method of DC motor?

A D.C shunt motor B D.C series motor C D.C differential compound motor

D D.C cumulative compound motor A Field diverter method B Field tapping method 9 Which rule determines the direction of C Voltage control method current in D.C motor? D Armature diverter method A Right hand grip rule 4 Which winding wire is used for DC field coil? B Right hand palm rule A Super enameled copper wire C Fleming’s left hand rule B Single silk covered copper wire D Fleming’s right hand rule C Double silk covered copper wire 10 What is the formula to calculate the current D PVC covered copper winding wire taken by D.C shunt motor armature? 5 Which formula is used to calculate the speed V A Ia = of DC motor? Ra

E Eb A N = b B Ia = φ Ra φ V − Eb B C Ia = N = R Eb a V + E E .φ D I = b C N = b a R 120 a E .φ 11 Which rule is applied to identify the direction D N = b 60 of flux in DC motor? A Cork’s screw rule

B Right hand grip rule

C Fleming’s left hand rule

D Fleming’s right hand rule

- Nimi Question Bank - Page1/ 8 12 Name the type of DC motor. 14 What is the name of the equipment?

A Shunt motor A Megger B Series motor B Earth resistance tester C Long shunt compound motor C Internal growler D Short shunt compound motor D External growler What is the formula to calculate back EMF in 13 15 What is the name of winding, if coil pitch is a DC motor? less than pole pitch? ZNP A Full pitch winding A Eb = φ 60 A B Half pitch winding N P C Long chorded winding B E = b Z φ 60 A D Short chorded winding φ Z N P C E = b 60 A 60 A φ D Eb = Z N P

- Nimi Question Bank - Page2/ 8 Questions: Level 2 8 What is the temperature value of class ‘F’ insulation? 1 What is the purpose of series resistor A 90°C connected with holding coil in a D.C four B 105°C point starter? C 120°C A Limit the current in holding coil D 155°C B Increase the current in holding coil 9 Which type of D.C motor is used for constant C Increase the voltage in holding coil speed drives? D Decrease the voltage in holding coil A DC series motor 2 Which speed control method of D.C B DC shunt motor series motor is used for electric train? C Differential long shunt compound motor A Field diverter method D Differential short shunt compound motor B Field tapping method 10 Which type of DC motor is used in elevators? C Armature diverter method A DC series motor D Supply voltage control method B DC shunt motor 3 Why shunt field coil is connected in series C DC differential compound motor with holding coil in D.C three point starter? D DC cumulative compound motor A Increase the holding coil current 11 Which method of speed control gives below B Decrease the holding coil current the rated speed in DC series motor? C Protect the shunt field from over current A Field diverter method D Protect the motor in case of open in shunt B Tapped field method field C Voltage control method 4 Why the direction of rotation is changed only D Armature diverter method by changing the armature current direction in 12 What is the effect, if a four point starter a D.C compound motor? resistance is cutoff during running? A Maintain rated speed A Motor stopped B Maintain motor characteristics B Runs at slow speed C Avoid armature reaction effect C Runs at very high speed D Prevent motor from over loading D Runs at reverse direction 5 Which speed control methods offers below 13 Why carbon composition brush requires in normal speed in DC shunt motor? the armature circuit to operate the D.C A Field control method motor? B Voltage control method A Increases the starting torque C Armature control method B Protects from armature reaction D Ward Leonard system of speed control C Protects armature from over loading 6 Why starters are required to start D.C motors D Reduces the spark in the commutator in industries? segment A Regulate the field voltage 14 Why series motor produce high torque and B Reduce the armature current speed initialy without load? C Control the armature reaction A Absence of back emf D Smooth operation of motors B Load current flows through field winding 7 Which insulating material belongs to class ‘B’ C Armature current and field current are same insulation? D Series field winding wound with thick wire A Cotton B Bamboo C Fibre glass D Leatheroid paper

- Nimi Question Bank - Page3/ 8 15 Why the series field is short circuted at the 21 Which growler test for armature is time of starting in differential compound illustrated? motor? A To reduce the starting current B To increase the speed of motor C To decrease the speed of motor D To maintain proper direction of rotation 16 Which is the most effective method of balancing armature? A Static balancing

B Dynamic balancing A Open coil test C Attached with counter balancing B Ground coil test D Plugged with lead weight balancing C Shorted coil test 17 Which material is used for starting resistance D Shorted commutator tests of DC starters? 22 Which speed control method is applied to A Eureka obtain both below normal and above normal B Nichrome speed in DC motor? C Manganin A Field control method D Constantine B Armature control method 18 Which DC compound motor is operated at C Tapped field speed control constant speed under varying load? D Ward Leonard speed control A Differential long shunt 23 Why commutators are sparking heavily? B Cumulative long shunt A Incorrect brush position C Differential short shunt B Incorrect field connection D Cumulative short shunt C Incorrect direction of rotation 19 How No volt coil is connected in a three point D Incorrect armature connection starter with DC shunt motor? 24 What is the action of the induced emf in a A Directly connected to supply running D.C motor? B Connected in series with armature A Assists the applied voltage C Connected in parallel with armature B Opposes the applied voltage D Connected in series with shunt field C Increases the armature current 20 Which type of armature winding is D Decreases the armature current illustrated? 25 Which motor has this characteristics curve?

A Series motor B Shunt motor

A Duplex lap winding C Cumulative compound motor B Triplex lap winding D Differential compound motor C Simplex lap winding D Quadruplex lap winding

- Nimi Question Bank - Page4/ 8 26 What is the purpose of resistor connected 33 Why the holding coil of a 3 point starter is with holding coil in 4 point starter? connected in series with shunt field? A Limit current in NVC A To limit the load current B Protect the coil from short circuit B To run motor at low voltages C Protect the motor from overload C To hold the handle plunger firmly D Protect the armature from short circuit D To protect the motor from high speed 27 Why the D.C series motor field winding is 34 What is the best method to change the DOR wound with thick wire? of a compound motor without change of its A To regulate field voltage characteristics? B To carry the load current A Change armature current direction C To keep maximum inductance B Change shunt field current direction D To reduce the armature reaction C Change series field current direction 28 Which type of speed control of D.C series D Change the current in armature and shunt motor? field together 35 What is the purpose of NVC connected in series with the field in 3 point starter? A To improve the torque B Reduce the field current C To decrease the back EMF D To prevent increase in speed A Field parallel method 36 Which type of DC motor is used for sudden B Field diverter method application of heavy loads? C Field tapping method A Shunt motor D Armature diverter method B Series motor 29 Which type of D.C motor is suitable for C Differential compound motors shearing machines? D Cumulative compound motors A Shunt motor 37 Which speed control method is used in food B Series motor mixture motors? C Cumulative compound motor A Voltage control method D Differential compound motor B Field diverter control method 30 Where D.C compound motors are preferred? C Armature diverter method A Constant load requirements D Series field tapping method B Constant speed requirements 38 Which speed control system provides a C High starting torque requirements smooth variation of speed from zero to D Constant speed under varying load above normal? requirements A Field control 31 What is the necessity of starter for D.C B Armature control motor? C Field diverter control A Limit the field current D Ward-Leonard system control B Limit the field voltage 39 What is the purpose of tapes in winding? C Control the motor speed A Insulate slots D Limit the armature current B Bind the coils 32 Which type of instrument is used to test the C Wrap the conductor armature winding? D Insulate exposed conductors A Megger B Growler C Multimeter D Ohmmeter

- Nimi Question Bank - Page5/ 8 40 Which type of DC armature winding the front 45 Which type of armature winding is

pitch (YF) is greater than back pitch (YB)? illustrated? A Lap winding B Wave winding C Progressive winding D Retrogressive winding 41 What reduces the cross sectional area of core material for VA rating? A Dynamo sheet B Low alloy sheet C High alloy sheet D Normal steel sheet A Triplex wave winding B Duplex wave winding 42 How to obtain opposite polarity in adjacent C Progressive lap winding poles into a 4 pole DC motor? D Retrogressive lap winding A Varying the number of turns in coil 46 Calculate the average pitch (Y ) for B Making series connection of coils A retrogressive wave winding, if C Making parallel connection of coils D Making current flow in different direction No. of armature conductor = 14 No. of slots = 7 43 What is the operation in the rewinding No. of poles = 2 process? A 4 B 6 C 8 D 14 47 Which type of test is illustrated for the armature after rewound?

A Cleaning of slots B Removing of winding C Removing of wedges D Cutting of winding wire 44 Which insulating material used in winding is a highly non-hygroscopic and possess good

electrical strength? A Open coil test A Empire cloth B Shorted coil test B Triplex paper C Voltage drop test C Millinex paper D Grounded coil test D Leatheroid paper 48 Why the newly rewound armature must be

preheated before varnishing?

A Drive out the moisture from it

B Help for quick drying of varnish

C Make easy to penetrate varnish inside

D Maintain uniform spreading of varnishing

- Nimi Question Bank - Page6/ 8 Questions: Level 3 5 What is the reason for reduction in speed of a D.C shunt motor from no load to full load? 1 How the direction of rotation of a DC compound motor is changed? A By changing the direction of armature current B By interchanging the supply terminals C By changing the direction of both field and armature current A Shunt field current increases D By changing the direction of series field B Shunt field current decreases current C Armature voltage drop increases 2 What is the effect, if a four point starter D Armature voltage drop decreases resistance is cutoff during running? 6 Which winding fault is determined by the A Motor stopped test? B Runs at slow speed C Runs at very high speed D Runs at reverse direction 3 What is the effect in a D.C shunt motor, if its supply terminals are interchanged? A Runs in slow speed B Runs in high speed C Runs in the same direction

D Runs in the reverse direction A Open coil fault 4 What is the speed, if field winding of a DC B Short coil fault shunt motor is in open circuit? C Grounded coil fault A Stop running D Grounded core fault B Motor runs normally C Runs at slow speed D Runs in very high speed

- Nimi Question Bank - Page7/ 8 Module 2: DC Motor - Key paper

Questions: Level 1 Questions: Level 2 Questions: Level 3

SL.No Key SL.No Key SL.No Key 1 D 1 A 1 A 2 C 2 A 2 C 3 D 3 D 3 C 4 A 4 B 4 D 5 A 5 C 5 C 6 A 6 B 6 A 7 C 7 C 8 A 8 D 9 D 9 B 10 C 10 D 11 C 11 D 12 D 12 B 13 C 13 D 14 D 14 A 15 D 15 D 16 B 17 A 18 B 19 D 20 A 21 A 22 D 23 A 24 B 25 C 26 A 27 B 28 A 29 C 30 D 31 D 32 B 33 D 34 A 35 D 36 D 37 D 38 D 39 C 40 D 41 C 42 D 43 C 44 C 45 C 46 B 47 B 48 A

- Nimi Question Bank - Page8/ 8 Electrician - 3rd Semester - Module 3 : AC Three Phase Motor

Question : Level 1 4 What is the name of the A.C motor starter?

1 What is the formula to calculate the slip

speed (Nslip) of 3 phase squirrel cage induction motor?

A Nslip = Ns −Nr

B Nslip = Nr −Ns Ns − Nr C Nslip = Nr Ns − Nr D Nslip = Ns 2 What is the type of control circuit?

A DOL starter B Auto transformer starter C Semi automatic star delta starter D Fully automatic star delta starter A Inching control 5 What is the formula to find synchronous B ON remote control speed of a A.C 3 phase induction motor? C OFF remote control 120F D Forward & reverse control A Synchronous speed = 3 Which formula is used to calculate the total P electrical degree in stator of an A.C motor? 120P B Synchronous speed = A Total electrical degree = 180° / no of slots F B Total electrical degree = 180° x no of slots 120 C Total electrical degree = 180° / no of poles C Synchronous speed = PF D Total electrical degree = 180° x no of poles PF D Synchronous speed = 120 6 What is the fuse rate to run a 10 HP three phase induction motor at full load? A 10 A B 15 A C 25 A D 30 A

- NIMI Question Bank - Page1/ 10 7 What is the name of the contact marked 11 What is the phase displacement between as ‘X’? windings in 3 phase motor? A 90° B 120° C 180°

X D 360° 12 What is the name of the part marked ‘X’?

A Star contact B Delta contact C Auxiliary contact D Over load relay contact 8 What is the type of A.C motor stator winding?

A Shaft B Brushes C Bearings D Slip rings 13 What is the name of AC coil winding? A Single layer basket winding B Double layer basket winding C Involute coil winding D Diamond coil winding 9 Which formula is used to calculate percentage slip of an AC 3 phase induction motor? A Half coil winding N −N A s r x 100 B Whole coil winding N s C Single layer winding N −N D Double layer winding B r s x 100 Ns 14 What is the name of the coil winding? N −N C s r x 100 Nr N −N D r s x 100 N r 10 Which operation the control circuit is used?

A Concentric coil winding B Distributed coil winding C Mesh shaped coil winding A Remote control D Diamond mesh shaped coil winding B Jogging/Inching C Sequential control D Forward and reverse

- NIMI Question Bank - Page2/ 10 15 Which speed is called as synchronous speed 20 What is the name of the starter symbol? in 3 phase induction motor? A No load speed B Full load speed C Rotating magnetic field speed D Relative speed between stator and rotor 16 What is the name of the starter symbol? A Star delta starter B Rheostatic starter C Direct on-line starter D Autotransformer starter 21 What is the formula to calculate pitch factor? A D.O.L starter Pole pitch B Auto transformer starter A Pitch factor = Winding pitch C Automatic star/delta starter D Semi automatic star/delta starter Winding pitch B Pitch factor = 17 Name the part marked ‘X’ of the winding Pole pitch machine? Number of slots C Pitch factor = Number of poles Number of poles D Pitch factor = Number of slots 22 How pole pitch is measured in terms of slots in AC winding? Total electrical degrees A Number of slots Number of slots B A Mandrel Total electrical degrees B Wire feed No of slots in the stator C C Wire guides No of poles D Spool carrier No of poles D 18 What is the electrical degree of 6 pole stator No of slots in the stator motor? 23 What is the formula to calculate the mean A 360° circumference of the coil? B 720° Lout −Lin C 1080° A Lm = cm 2 D 1440° Lin + Lout 19 Calculate the number of coils per phase per B Lm = cm 2 pair of poles of 3 phase motor having 2 pole, 2 24 slots,12 coils? C Lm = cm L − L A 1 out in B 2 2 D Lm = cm C 3 Lin + Lout D 4

- NIMI Question Bank - Page3/ 10 Question : Level 2 7 Why pre heating is necessary for motors before varnishing in rewinding process? A To dry the varnish quickly in winding 1 What is the synchronous speed of a A.C 3 B To easy flow of varnish in the winding phase induction motor having 6 poles at a C To increase the insulation resistance value frequency of 50 Hertz? D To drive out the moisture in between winding A 800 rpm layers B 1000 rpm C 1200 rpm 8 Which type of test is conducted using D 1440 rpm internal growler in AC motor winding? A Ground test 2 Calculate the percentage slip in a 3 phase B Polarity test induction motor having 6 poles with a C Continuity test frequency of 50 Hertz rotating with actual speed of 960 rpm? D Short circuit test A 2% 9 Which device is used to test startor winding B 3% short and open fault? C 4% A Tong Tester D 5% B Internal Growler 3 What is the rotor frequency of a 3 phase C External Growler squirrel cage induction motor at the time of D Digital multimeter starting? 10 What is the purpose of using thermal cutout A Equal to supply frequency in addition to fuse in A.C motor circuit? B 3 times less than supply frequency A Protect from heavy load C 3 times more than supply frequency B Protect against high voltage C Allow for continuous over loading D 3 times less than supply frequency D Protect against dead short circuit 4 How the voltage is received in the rotor of 11 Which type of motor is used to provide high induction motor? starting torque at variable speed? A Direct connection from stator A Universal motor B Due to back emf produced in stator B Permanent capacitor motor C Direct connection to rotor from supply C 3 Phase slip ring induction motor D By the transformer action of stator and rotor D 3 Phase single squirrel cage induction motor 5 Which method is applied to control the 12 What is the relation between torque and slip speed of 3 phase squirrel cage induction in an A.C induction motor? motor from its rotor side? A Slip increases torque decreases A Cascade operation B Slip increases torque increases B Changing applied voltage C Slip decreases torque increases C Changing applied frequency D Slip decreases torque decreases D Changing the number of poles 13 What is effect of A.C induction motor if rotor 6 Which loss of 3 phase induction motor is bar is in open circuit ? determined by blocked rotor test? A Vibration of shaft A Copper loss B Motor will not start B Friction loss C Runs in slow speed C Hysteresis loss D Over heating of motor D Eddy current loss

- NIMI Question Bank - Page4/ 10 14 Which type of wire is used for rewinding of 22 Which instrument is used to measure A.C 3 phase motors? insulation resistance of a 3 phase induction A Super enamelled copper wire motor? B PVC covered copper winding wire A Megger C Single cotton covered copper wire B Multimeter D Double cotton covered copper wire C Shunt type ohmmeter 15 Which material is used as wedges in D Series type ohmmeter winding process? 23 Which test in winding is illustrated? A Empire B Cotton C Bamboo D Terylene 16 Which test in winding is essential before giving supply? A Ground test B Polarity test A Polarity test C Open circuit test B Ground test D Short circuit test C Continuity test 17 Why the rotor bars are mounted in a slightly D Short circuit test skewed position in 3 phase motor? 24 What is the starting current of an A.C 3 A Generate maximum flux phase induction motor? B Reduce the stray losses A 1 to 2 times of full load current C Maintain the rotor speed constant B 2 to 3 times of full load current D Produce more uniform rotor field and torque C 4 to 5 times of full load current 18 Which loss is determined by no load test of 3 D 5 to 6 times of full load current phase induction motor? 25 Which method is used to control the speed of A Iron loss 3 phase induction motor from stator side? B Copper loss A By cascade operation C Friction loss B By rotor rheostat control D Windage loss C By injecting emf in rotor circuit 19 Which method of speed control two variable D By changing the applied frequency speeds only obtained in 3 phase motor? 26 What is the speed control method of 3 phase A By rotor rheostat control induction motor? B By changing applied frequency C By changing the applied voltage D By changing the number of stator poles 20 Why slip ring induction motor is fitted with wound rotor? A To reduce the slip B To control the speed C To reduce the losses

D To get high starting and running torque A Cascade operation method 21 What is the function of timer in automatic star B Rotor rheostat control method delta starter? C Changing applied voltage method A Trip at over load D Injecting emf in rotor circuit method B Switch ON at pre set time C Change from star to delta D Switch OFF at pre set time

- NIMI Question Bank - Page5/ 10 27 What are the two functional circuits 34 What is the type of rewinding process? incorporated with a three phase motor starter? A Open circuit and short circuit B Closed circuit and open circuit C Short circuit and closed circuits D Control circuit and power circuit 28 Which is the main property of leatheroid A Hand winding paper insulation? B Skein winding A Non moisturized material C Former winding B Highly non-hygroscopic D Machine winding C Very good for class F insulation D Better ageing and dielectric strength 35 What is the purpose of using thermal cutout in addition to fuse in motor circuits? 29 Which type of insulating material is selected A Over load protection for binding the coils and over hangs? B Over voltage protection A Cotton sleeves C Dead short circuit protection B Empire sleeves C Terylene thread D Continuous over loading protection D Fibre glass tape 36 Which type of starter is used to start and run 30 Which insulation is used for cuffing in AC the 3 phase slip ring induction motor? winding? A Direct on-line starter A Fibre glass tape B Rotor rheostat starter B Leatheroid paper C Auto transformer starter C Empire fiber glass tape D Manual star-delta starter D Fabric based adhesive tape 37 Which copper wire is used to wind small 31 What refers coil in AC winding? capacity transformers? A Number of turns connected in series A PVC coated copper wire B Number of turns connected in parallel B Cotton covered copper wire C Number of turns under two similar poles C Super enameled copper wire D Number of turns under two dissimilar poles D Silk cotton covered copper wire 32 Which type of AC winding the number of 38 What is the function of collar? coil/pole/phase is more than one at different pitches? A Involute coil winding B Diamond coil winding C Flat loop over lapped winding

D Flat loop non-over lapped winding 33 Calculate the number of coils /phase/ pole

for a 3 phase double layer distributed A Provides insulation around field winding for a motor having 36 slots, 36 coils B Provides insulation for coil tapping and 4 poles? C Helps tightening material for flange A 3 coils /phase/ pole D Provides insulation for heat transfer from coil B 6 coils / phase/pole 39 Which type of winding wire is used to wind C 9 coils / phase/pole submersible pump motors? D 12 coils/ phase/ pole A PVC covered type B Terylene thread type C Super enamelled type D Double cotton covered type

- NIMI Question Bank - Page6/ 10 40 What is the reason of long chord winding is 46 Which method of speed control is only avoided in AC motors? applicable for 3 phase slipring induction A Low efficiency motor? B Low starting torque A Cascade operation method C More winding wire required B Rotor rheostat speed control D Control the increased heat loss C Changing the applied frequency method 41 Which type of winding has more space for D Changing the number of stator poles method cooling? 47 What is the name of the winding? A Between overhanging coils B Between overhanging coil and rotor C Between overhanging coils and yoke

D Between overhanging coil and wedge 42 Where the panel boards are used? A Industrial motor drives B Domestic wiring circuits C 3 phase domestic wiring D Load distribution for AC & DC supply A Skew winding 43 Determine the torque in newton metres B Skein winding produced by a 7.5 HP squirrel cage motor C Involute coil winding rotating at 1440 rpm? D Diamond coil winding A 21.63 Nm 48 What is the name of 3 phase motor winding, B 24.4 Nm if the coil pitch is less than pole pitch? C 33.05 Nm A Full pitch winding D 36.6 Nm B Whole coil winding 44 Which type of handle design of rotary switch C Long chorded winding is illustrated? D Short chorded winding 49 Which is the demerit of 3 phase concentric winding? A More space is required B A stepped former is required C More difficult to shape the coils uniformly D It is not easy to make the end connection 50 What is the name of the diagram used for 3phase motor winding? A Knob B Lever C Coin slot D Key operation 45 What is the purpose of using rotor resistance starter to start 3 phase slip ring induction motor?

A Reduce rotor voltage A Ring diagram B Reduce rotor current B Development diagram C Increase the torque C Coil connection diagram D Reduce the power loss D End connection diagram

- NIMI Question Bank - Page7/ 10 51 Calculate the phase displacement in terms of 53 Which type of testing of winding is slots for a 3 phase, 36 slots, 12 coils, 4 pole illustrated? stator winding? A 3 slots B 4 slots C 6 slots D 8 slots

52 Which type of AC motor winding having the A Polarity test number of coil/pole/phase is more than one B Resistance test arranged in different slots? C Short circuit test A Basket winding D Voltage drop test B Concentric winding C Distributed winding D Concentrated winding

- NIMI Question Bank - Page8/ 10 Question : Level 3 8 What happens to the rotor of a 3 phase induction motor if its speed attains to 1 Why external resistance is included in the synchronous speed? rotor circuit at starting through 3 phase A Rotor speed reduces slipring induction motor starter? B Rotor speed increases A To get high running torque C Rotor speed remains same B To get high starting torque D Rotor bars get damaged C To reduce the load current 9 What is the effect of open circuit in rotor of D To get increased speed at starting an induction motor? 2 What is the effect of motor, if the rotor A Motor does not start windings in slipring induction motor is open B Over heating in motor circuited at starting? C Excess vibration of shaft A Will not run D Motor runs with very low speed B Runs at slow speed 10 What is the reason for frequent blowing of C Runs at very high speed fuse after motor running some time? D Runs but not able to pull load A Improper earthing 3 What happens to a 3 phase induction B Over loading of motor motor if one phase fails during running? C Heavy voltage fluctuation A Motor runs normally D Poor insulation in winding B Motor stop instantaneously 11 What happens to a 3 phase induction motor, C Motor runs slowly, finally it burns if one phase fails during starting? D Motor runs with irregular speed A Motor runs and stop immediately 4 What is the effect on 3 phase induction B Motor runs in slow speed continuously motor if one phase is cut-off during running C Motor runs and draws more current with load? D Motor continues to run with irregular speed A Motor stops at once 12 Which is the cause for the 3 phase motor B Motor will run normally starter with single phase preventer trips C Motor runs with humming noise with slow frequently? speed A Incorrect fuse ratings D Motor will run slow speed but winding will be B Unbalanced line voltages burnt out shortly C Incorrect settings of OLR 5 What is the defect if starter with single D Improper phase sequence phasing preventer does not switch ‘ON’? 13 What indication denotes the shorted coil A Improper phase sequence defect in 3 phase motor stator winding while B Fluctuations in line voltage testing with internal growler by keeping C Loose contact in supply lines hacksaw blade? D Wrong terminal connections at motor A Hacksaw blade gets over heated 6 What is the defect in AC 3 phase induction B Rapid vibration of hacksaw blade motor runs at low speed if loaded? C Hacksaw blade repels against the slots

A Wrong motor connection D Attracted by the winding turns on the slot B Wrong starter connection C Open circuit in rotor winding D Partially shorted in stator winding 7 Which fault condition thermal overload relay protects A.C induction motor? A Short circuit B Open circuit C Over current D Under voltage

- NIMI Question Bank - Page9/ 10

Module 3: AC Three phase motor - Key paper

Questions: Level 1 Questions: Level 2 Questions: Level 3

SL.No Key SL.No Key SL.No Key SL.No Key 1 A 1 B 46 B 1 B 2 A 2 C 47 A 2 A 3 D 3 A 48 D 3 C 4 B 4 D 49 B 4 D 5 A 5 A 50 A 5 A 6 C 6 A 51 C 6 D 7 C 7 D 52 C 7 C 8 A 8 D 53 B 8 D 9 A 9 B 9 D 10 B 10 C 10 D 11 B 11 C 11 A 12 D 12 B 12 C 13 B 13 D 13 B 14 D 14 A 15 C 15 C 16 B 16 B 17 A 17 D 18 C 18 A 19 D 19 D 20 A 20 D 21 B 21 C 22 C 22 A 23 B 23 A 24 D 25 D 26 A 27 D 28 D 29 C 30 D 31 A 32 D 33 A 34 A 35 D 36 B 37 C 38 A 39 A 40 C 41 C 42 C 43 D 44 C 45 C

- NIMI Question Bank - Page10/ 10 Electrician - 3rd Semester - Module 4 : AC Single Phase Motor

Questions : Level 1 3 What is the working principle of single phase induction motor? 1 What is the working principle of single phase A Lenz’s law induction motor? B Joule’s law A Lenz’s law C Faraday’s laws of electrolysis B Joule’s law D Faraday’s laws of electromagnetic induction C Faraday’s laws of electrolysis 4 Which type of single phase motor is D Faraday’s laws of electromagnetic induction illustrated? 2 What is the name of single phase motor?

A Permanent capacitor motor A Universal motor B Induction start capacitor run motor B Permanent capacitor motor C Capacitor start capacitor run motor C Capacitor start induction run motor D Capacitor start induction run motor D Capacitor start capacitor run motor

- NIMI Question Bank - Page1/ 6 Questions : Level 2 6 Which type of AC single phase motor having low starting torque? A Induction start induction run motor 1 Which type of A.C single phase motor is B Capacitor start induction run motor classified under commutator motor type? C Capacitor start capacitor run motor A Stepper motor D Resistance start induction run motor B Repulsion motor C Shaded pole motor 7 What is the function of centrifugal switch in D Permanent capacitor motor single phase motors? A Maintain constant speed 2 Which method is adopted to start the single B Break the starting winding phase induction motor? C Break the running winding A Split phase method D Protect the motor from over loading B Varying supply voltage method C Reversal of input supply terminals 8 Which is the application of universal motor? D Reversal of running coil connection A Jet pump B Food mixer 3 What is the type of A.C single phase motor? C Teleprinter D Compressor 9 Which single phase motor is fitted with wound rotor? A Repulsion motors B Shaded pole motors C Permanent capacitor motors

D Capacitor start capacitor run motors A Permanent capacitor motor B capacitor start capacitor run motor 10 What is the relation between running winding C Induction start induction run motor and starting winding of a single phase D Capacitor start induction run motor induction motor with respect to resistance? A Both resistances will be equal 4 Marks : 3 B Running winding is less, starting winding What is the purpose of the capacitor (C) in more centrifugal switch speed control method of C Running winding is more, starting winding universal motor? less D Running winding is less, starting winding infinity 11 What is the function of the part marked ‘x’ in shaded pole motor?

A Maintain constant speed B Improve the power factor C Protect from the over loading D Reduce the sparks on the contacts 5 Which type of winding wire is used for rewinding submersible pumps? A Increase the efficiency A PVC covered copper wire B Maintain constant speed B Super enamelled copper wire C Initiate the rotor movement C Single cotton covered copper wire D Strengthen the magnetic field D Double cotton covered copper wire

- NIMI Question Bank - Page2/ 6 12 How the direction of rotation of a capacitor 19 What is the function of centrifugal switch in start induction run motor is reversed? single phase motor? A By changing the supply terminals A Protects from over current B By changing the capacitor connections B Maintains constant speed C By interchanging main winding terminals C Protect the motor from over loading D By interchanging both main and auxiliary D Make and break the starting winding from winding terminals supply 13 Which single phase motor tapped field speed 20 How to produce starting torque in a shaded control method is employed? pole fan motor? A Universal motor A Using rings on poles B Shaded pole motor B Using capacitor on winding circuits C Capacitor start induction run motor C Interchanging cage rotor windings by switch D Capacitor start capacitor run motor D Interchanging the field coil windings by 14 Which type of single phase induction motor switch is used in food mixer? 21 What is the reason to use a permanent A Universal motor capacitor in fan motor circuit? B Repulsion motor A Speed regulation C Shaded pole motor B Lower power consumption D Permanent capacitor motor C Splitting of phase for torque 15 What is the angular displacement between D Controlling electrical interference starting and running winding of a single 22 Which motor is having half coil winding? phase induction motor? A Mixer A 45 electrical degree B Grinder B 60 electrical degree C Ceiling fan C 90 electrical degree D Washing machine D 120 electrical degree 23 Why running winding is placed in the bottom 16 Why the hysteresis motor is suitable for of the core? sound recording instruments? A To get low resistance A Small in size B To get low inductance B High efficiency C To get high resistance C Noiseless operation D To get high inductance D Less error operation 24 Calculate the slot distance for a ceiling fan 17 Which motor is preferred for domestic water having 28 slots, 14 poles, 14 coils in half coil pumps? connection? A Universal Motor A 90° B Repulsion motor B 120° C Shaded pole motor C 180° D Capacitor start motor D 240° 18 Which type of motor has relatively small 25 What is the application of shaded pole starting torque? motor? A Universal motor A Hair dryer B Capacitor start capacitor run motor B Ceiling fan C Capacitor start induction run motor C Wet grinder D Resistance start induction run motor D Washing machine

- NIMI Question Bank - Page3/ 6 26 Which type of single phase motor is used for 28 Which type of single phase motor is having hard disk drives? very high starting torque than any other type A Stepper motor of single phase motor? B Repulsion motor A Universal motor C Hysteresis motor B Reluctance motor

D Reluctance motor C Repulsion start induction run motor 27 What is the function of centrifugal switch D Capacitor start induction run motor used in capacitor start, capacitor run 29 Where the capacitor is connected in a single induction motor? phase permanent capacitor motor? A Disconnect the running winding after A In series with starting winding reached 75% to 80% speed B In series with running winding B Disconnect the starting winding after reached C In parallel with starting winding 75% to 80% speed D In parallel with running winding C Disconnect the starting capacitor after 30 Which motor is used in table fan? reached 75% to 80% speed A Universal motor D Disconnect the starting and running winding B Shaded pole motor

after reached 75% to 80% speed C Eddy current motor D Permanent capacitor motor

- NIMI Question Bank - Page4/ 6 Questions : Level 3 4 How the direction of rotation of repulsion motors is to be reversed? 1 What is the effect, if coil group connection is A By shifting the brush-axis wrongly connected in a single phase motor B By interchanging the supply terminals rewinding? C By changing the main winding terminals A Motor runs slowly D By changing the compensating winding B Motor will not run terminals C Motor runs in very high speed 5 Why a capacitor is connected across D Motor runs and takes more current at no load centrifugal switch in the centrifugal switch 2 What is the effect in a repulsion motor, if the speed control method? magnetic axis shifted to another side? A To maintain constant speed B To protect from over loading C To improve the power factor D To reduce the sparks in contacts 6 What is the effect, if some slots in a split phase motor left out without winding after completion of concentric winding? A Works normally B Reduction in speed C Reduction in torque D Runs with very high speed 7 How the radio interference can be

A Direction of rotation will change suppressed in centrifugal switch method of B Direction of rotation remains same speed control of universal motor? C Motor speed increases from rated speed A By connecting capacitor across centrifugal D Motor speed will reduce from rated speed switch 3 What is the effect if the centrifugal switch is B By connecting capacitor in series with not disconnected after the motor starts? centrifugal switch A Motor will run normally C By adding compensating winding with B Motor will stop immediately armature C Starting winding will burn out D By connecting an inductor in series with D Motor will run very slow speed centrifugal switch D Poor insulation in winding

- NIMI Question Bank - Page5/ 6

Module 4: AC Single Phase Motor - Key paper

Questions: Level 1 Questions: Level 2 Questions: Level 3

SL.No Key SL.No Key SL.No Key 1 A 1 B 1 B 2 A 2 A 2 A 3 A 3 D 3 C 4 D 4 D 4 D 5 A 5 D 6 D 6 A 7 B 7 A 8 B 9 A 10 B 11 C 12 C 13 A 14 A 15 C 16 C 17 D 18 D 19 D 20 A 21 C 22 C 23 D 24 A 25 A 26 A 27 C 28 A 29 A 30 D

- NIMI Question Bank - Page6/ 6 Electrician - 3rd Semester - Module 5 : Alternator

Questions : Level 1 5 How alternators are rated? A KVA 1 Which formula is used to calculate B KW EMF/phase in a ideal alternator? C MW D KV φFT A E= 2.22 6 Which formula is used to calculate the percentage voltage regulation in alternator? φFT B E= V − V 4.44 A FL NL x 100 V C E = 2.22 φ FT FL D E = 4.44 φ FT V − V B NL FL x 100 2 Which rule is used to find the direction of V FL induced emf in an alternator? V − V A Cork screw rule C NL FL x 100 V B Right hand palm rule NL C Fleming’s left hand rule V − V D FL NL x 100 D Fleming’s right hand rule V NL 3 What is the name of the part of alternator? 7 What is the formula to calculate R.M.S value of emf / phase if ‘T’ is number of turns of alternator? A E = 4.44 FT B E = 2.22 ɸ T C E = 2.22 ɸ FT D E = 4.44 ɸ FT 8 What is the supply frequency of an alternator A Stator having 6 poles runs at 1000 rpm? B Exciter A 25 Hz C Salient pole rotor B 40 Hz D Smooth cylindrical rotor C 50 Hz 4 What is the formula to calculate emf D 60 Hz equation of an alternator?

A E = 4.44 Kd Kc T φ m

B E = 2.22 Kd Kc F φ m

C E = 4.44 Kd Kc FT φ m

D E = 1.11 Kd Kc F φ m

- NIMI Question Bank - Page1/ 5 Questions : Level 2 8 What is the speed of an alternator connected with a supply frequency of 50 Hz at rated 1 Calculate the speed of an alternator having voltage having 4 poles? A 1000 rpm 2 poles at a frequency of 50 Hz? B 1500 rpm A 1500 rpm C 3000 rpm B 2500 rpm D 4500 rpm C 3000 rpm 9 What condition the two lamps become bright D 6000 rpm and one lamp dark during paralleling of two 2 What condition the lamps become dark in alternators? dark lamp method of parallel operation of two A Terminal voltages are equal alternators? B Voltages and frequencies are equal A Terminal voltages are equal C Voltages and phase sequence are equal B Voltage and frequency are equal D Both the alternators receive same frequency C Voltage and power rating are equal 10 What causes the terminal voltage of an D Frequency are same in both alternator alternator reduces, if the load increases? 3 How to compensate de-magnetizing effect A Field resistance due to armature reaction in an alternator? B Armature reaction A Reducing the speed of alternator C Inductive reactance B Reducing field excitation current D Armature resistance C Increasing field excitation current 11 What is the purpose of using damper winding D Increasing the speed of alternator in alternator? 4 What is the use of synchroscope? A Prevents heating A Adjust the output voltage B Reduces copper loss B Adjust the phase sequence C Reduces windage loss C Adjust the supply frequency D Prevents the hunting effect D Indicate the correct instant for paralleling 12 What is the type of alternator? 5 What is the name of the equipment that provides D.C to the rotor of alternator? A Exciter B Inverter C Converter D Synchroniser 6 What is the purpose of damper winding in

alternator? A Brushless alternator A Reduces the copper loss B Three phase alternator B Reduces windage losses C Single phase alternator C Reduces the hunting effect D Salient pole type alternator D Improves the voltage regulation 13 Calculate the speed in r.p.s of the 2 pole,

7 Which condition is to be satisfied before 50HZ alternator? parallel operation of alternators? A 50 rps A Rating must be same B 100 rps B Phase sequence must be same C 1500 rps C Rotor impedance must be same D 3000 rps D Stator impedance must be same

- NIMI Question Bank - Page2/ 5 14 What is the advantage of using rotating field 15 What is the effect in increasing the field type alternator? excitation current in alternator? A Easy to locate the faults in the field A Prevents demagnetizing B Easy to connect the load with alternator B Over voltage protection C Easy to dissipate the heat during running C Dead short circuit protection D Two slip rings only required irrespective of D Alternator will be over loaded No. of phases

- NIMI Question Bank - Page3/ 5 Questions : Level 3 3 How to compensate de-magnetizing effect due to armature reaction in an alternator?

1 Calculate the pitch factor (KP) for a winding A By reducing the speed of alternator having 36 stator slots 4 pole with angle (α) is B By increasing the speed of alternator 30° in alternator? C By increasing the field excitation current A 0.942 D By decreasing the field excitation current B 0.965 4 Calculate the voltage regulation in C 0.978 percentage if the load is removed from an D 0.985 alternator, the voltage rises from 480V to 2 What is the cause for hunting effect in 660V? alternators? A 27.2% A Due to over load B 32.5% B Running without load C 37.5% C Running with fluctuation of speed D 38.5%

D Due to continuous fluctuation in load

- NIMI Question Bank - Page4/ 5

Module 5: Alternator - Key paper

Questions: Level 1 Questions: Level 2 Questions: Level 3

SL.No Key SL.No Key SL.No Key 1 D 1 C 1 B 2 D 2 B 2 D 3 C 3 C 3 C 4 C 4 D 4 C 5 A 5 A 6 B 6 C 7 D 7 B 8 C 8 B 9 B 10 D 11 D 12 A 13 A 14 D 15 A

- NIMI Question Bank - Page5/ 5 Electrician - 3rd Semester - Module 6 : Synchronous Motor and MG Set

Questions : Level 1 2 What is the name of the converter?

1 What is the name of the converter?

A Metal rectifier B Rotary convertor A Metal rectifiers C Mercury arc rectifier B Rotary convertor D Silicon controlled rectifier C Mercury arc rectifiers D Motor-Generator set

- NIMI Question Bank - Page1/ 4 Questions : Level 2 9 What is the advantage of motor generator set? 1 Why D.C supply is necessary for A Noiseless synchronous motor operation ? B High efficiency A Reduce the losses C Low maintenance required D DC output voltage can be easily controlled B Start the motor initially C Run the motor with over load 10 What is the function of the part marked ‘X’ of D Run the motor at synchronous speed the rotary converter? 2 Which acts as both inverter and converter? A Metal rectifier B Mercury arc rectifier C Semi conductor diode D Synchronous converter 3 What is the function of inverter? A Convert A.C to D.C B Convert D.C to A.C C Smoothening A.C sine wave

D Convert pulsating DC into pure D.C A Converts AC to DC 4 Which converting device can be over B Reduces voltage drop loaded? C Helps to deliver without noise A Rectifier unit D Collects the delivered direct current B Rotary converter 11 Why D.C supply is necessary for C Motor generator set synchronous motor operation? D Mercury arc rectifier A Reduce the losses 5 Why exciter is essential to run a B Start the motor initially synchronous motor? C Run the motor with over load A Carry more load in motor D Run the motor at synchronous speed B Improve the power factor 12 Which acts as both inverter and converter? C Reduce the losses in motor A Metal rectifier D Run the motor at synchronous speed B Mercury arc rectifier 6 Which application requires only DC? C Semi conductor diode A Electroplating D Synchronous converter B Stepping up of voltage 13 What is the purpose of damper winding in a C Operating induction motor synchronous motor at starting? D Operating repulsion motor A Produce high voltage to initiate the rotation 7 Why the LED’s are avoided as converters in B Produce high current to start rotate the motor rectifier diodes? C Produces torque and runs near in A Heavily doped device synchronous speed B Very low power device D Produce a high magnetic-field to maintain a C Designed for light emitting constant speed D Very sensitive to temperature 8 Which is the main application of synchronous motors? A Elevators B Paper rolling mills C AC to DC converter D Power factor correction device

- NIMI Question Bank - Page2/ 4 Questions : Level 3 4 Which converter is having high efficiency? 1 Why the synchronous motor fails to run at A SCR converter synchronous speed? B Rotary converter A In sufficient excitation C Motor generator set B Defective pony motor D Mercury arc rectifier C Open in damper winding 5 How synchronous motor works as a power D Short in damper winding factor corrector? 2 How the synchronous motor is used as a A Varying the line voltage synchronous condenser? B Varying the field excitation A Varying the motor load C Increasing the speed of motor B Varying the rotor excitation D Decreasing the speed of motor C Varying stator voltage in motor D Varying stator current in motor 3 What is the function of damper windings in synchronous motor? A Maintain power factor B Excite the field winding C Maintain constant speed D Start the synchronous motor

- NIMI Question Bank - Page3/ 4 Module 6: Synchronous Motor and MG set - Key paper

Questions: Level 1 Questions: Level 2 Questions: Level 3

SL.No Key SL.No Key SL.No Key 1 D 1 D 1 A 2 B 2 D 2 B 3 B 3 D 4 A 4 A 5 D 5 B 6 A 7 B 8 D 9 D 10 D 11 D 12 D 13 D

- NIMI Question Bank - Page4/ 4