122 + Interview Questions in Synchronous Machines in Electrical Machines Page 2 InterviewSolution

51.	The active power delivered by an alternator will _______ when the prime mover input is increased for the alternator connected to infinite bus bar.(a) increases(b) decreases(c) remains constant(d) no relation exists between the power andprime mover droop characteristicThe question was asked in quiz.The doubt is from Power Factor Control of Synchronous Machines in portion Synchronous Machines of Electrical Machines
Answer» The CORRECT ANSWER is (a) increases To explain: The LOAD angle will increase and so the real POWER will increase in CASE the prime mover input is increased.

Discussion

52.	The operating frequency and voltage of an isolated alternator ________ if the prime mover input to motor is increased.(a) increases(b) decreases(c) remains constant(d) no relation exists between the power and frequencyI had been asked this question in an interview for job.This interesting question is from Power Factor Control of Synchronous Machines in section Synchronous Machines of Electrical Machines
Answer» Correct option is (a) increases For EXPLANATION: By varying the PRIME mover TORQUE, the LOAD angle as well as the operating frequency also get affected.

Discussion

53.	For a synchronous motor, mark the appropriate.(a) A-Inductor, B-Capacitor(b) A-Capacitor, B-Resistor(c) A-Inductor, B-Inductor(d) A-Capacitor, B-InductorThe question was asked in an interview for job.Question is taken from Power Factor Control of Synchronous Machines topic in division Synchronous Machines of Electrical Machines
Answer» Right ANSWER is (a) A-Inductor, B-Capacitor For EXPLANATION: A will act as the inductor curve CONSUMING the reactive power while the B curve is LIKE capacitor.

Discussion

54.	Synchronous compensators are __________(a) overexcited synchronous motor with no mechanical load(b) overexcited synchronous motor with mechanical load(c) underexcited synchronous motor with no mechanical load(d) normal excited synchronous motor with no mechanical loadThis question was addressed to me in an online interview.My doubt stems from Power Factor Control of Synchronous Machines in chapter Synchronous Machines of Electrical Machines
Answer» Right ANSWER is (a) overexcited synchronous motor with no mechanical LOAD The BEST I can explain: Synchronous COMPENSATORS are overexcited synchronous motor with no mechanical load.

Discussion

55.	For a power system having induction motor loads, an overexcited synchronous motor is also attached. The induction motor will now operate at __________(a) lagging(b) leading(c) reduced power factor(d) increased power factorI got this question during an online exam.My question is based upon Power Factor Control of Synchronous Machines topic in chapter Synchronous Machines of Electrical Machines
Answer» Right CHOICE is (a) lagging For EXPLANATION: Adding synchronous motor will improve the pf of the SYSTEM but then the induction motor will STILL WORK at lagging pf only.

Discussion

56.	The inverted V plots is plotted between __________(a) power factor vs field current for constant shaft load(b) field current vs power factor for variable shaft load(c) armature current vs field current(d) terminal voltage vs power factorThe question was asked in an international level competition.The above asked question is from Power Factor Control of Synchronous Machines in chapter Synchronous Machines of Electrical Machines
Answer» Correct option is (a) power FACTOR vs FIELD current for constant SHAFT load Best explanation: inverted v-curves are PLOTTED between power factor and field current for constant shaft load.

Discussion

57.	For a power system having induction motor loads, an overexcited synchronous motor is also attached. Then the over all power factor __________(a) improves(b) degrades(c) becomes upf(d) remains sameI got this question in an interview for internship.The origin of the question is Power Factor Control of Synchronous Machines topic in portion Synchronous Machines of Electrical Machines
Answer» The CORRECT choice is (a) improves To EXPLAIN I WOULD SAY: An over excited synchronous motor acts as a source of lagging REACTIVE power and so the overall power factor improves.

Discussion

58.	The armature current is _______ at UPF than motor at lagging power factor.(a) minimum(b) maximum(c) zero(d) none of the mentionedThis question was posed to me by my college director while I was bunking the class.My question is taken from Power Factor Control of Synchronous Machines in section Synchronous Machines of Electrical Machines
Answer» The correct CHOICE is (a) minimum For explanation: At LEADING pf ARMATURE current will be HIGH as the emf will be high for a synchronous MOTOR.

Discussion

59.	The armature current is ________ at UPF when compared to leading power factor for a motor.(a) minimum(b) maximum(c) equal(d) none of the mentionedI have been asked this question by my school teacher while I was bunking the class.My query is from Power Factor Control of Synchronous Machines topic in division Synchronous Machines of Electrical Machines
Answer» The correct choice is (a) minimum For explanation: At leading pf ARMATURE CURRENT will be HIGH as the EMF will be high.

Discussion

60.	When the excitation voltage is increased from 1 to 1.3 pu of a 3-phase synchronous motor. Then load angle for the constant power operation __________(a) must be decreased(b) can also be increased(c) increased(d) decreasedI got this question in a national level competition.I need to ask this question from Power Factor Control of Synchronous Machines topic in chapter Synchronous Machines of Electrical Machines
Answer» The correct OPTION is (a) must be decreased The BEST EXPLANATION: Efsinδ is to be maintained constant. so if excitation VOLTAGE increases then the load ANGLE must decrease.

Discussion

61.	When a constant power output is desired to maintain __________(a) Efsinδ and Iacosθ are to be maintained constant(b) Efsinδ is be maintained constant(c) Iacosθ is to be maintained constant(d) Efsinδ and Iasinθ are to be maintained constantThe question was posed to me by my college director while I was bunking the class.Origin of the question is Power Factor Control of Synchronous Machines topic in chapter Synchronous Machines of Electrical Machines
Answer» Correct choice is (a) Efsinδ and Iacosθ are to be MAINTAINED constant To explain: For constant REAL power output the component of the EXCITATION voltage lagging to Vt should remain constant as PER the PHASOR diagram.

Discussion

62.	The V-curves of synchronous motor is plotted between ________(a) Ia Vs If with constant shaft load(b) If Vs Ia with constant shaft load(c) power factor vs If(d) power factor vs IaThe question was asked in an interview.Question is from Power Factor Control of Synchronous Machines in chapter Synchronous Machines of Electrical Machines
Answer» Correct choice is (a) IA VS If with constant shaft load For EXPLANATION I would say: The V-curves of synchronous motor is PLOTTED between Ia Vs If with constant shaft load.

Discussion

63.	The excess flux in synchronous motor is neutralized by __________(a) armature winding by drawing demagnetizing component of the current from ac supply(b) armature winding by drawing magnetizing component of the current from ac supply(c) fieldwinding by drawing demagnetizing component of the current from dc supply(d) field winding by drawing magnetizing component of the current from dc supplyI got this question during an interview.Question is taken from Power Factor Control of Synchronous Machines topic in chapter Synchronous Machines of Electrical Machines
Answer» The CORRECT ANSWER is (a) armature WINDING by drawing demagnetizing component of the current from ac supply To explain: Excess flux is NEUTRALIZED y the demagnetizing component.

Discussion

64.	A 3 phase synchronous motor is working at normal excitation, then the flux deficient in circuit is ________(a) given by armature winding mmf(b) given by field winding mmf(c) supplied to armature winding mmf(d) supplied to field winding mmfThis question was addressed to me by my school principal while I was bunking the class.I'm obligated to ask this question of Power Factor Control of Synchronous Machines in section Synchronous Machines of Electrical Machines
Answer» The correct answer is (a) GIVEN by ARMATURE winding MMF To elaborate: it is given by armature winding mmf.

Discussion

65.	The magnetization current drawn from an AC supply a synchronous motor is used to _________(a) set up flux in magnetic circuit of device(b) compensate core losses(c) set up magnetizing armature reaction(d) all of the mentionedThis question was addressed to me during an interview.My enquiry is from Power Factor Control of Synchronous Machines topic in portion Synchronous Machines of Electrical Machines
Answer» The correct answer is (a) set up FLUX in magnetic circuit of device To explain I WOULD say: Magnetizing current SETS up the flux NEEDED in the machine.

Discussion

66.	During the starting of the 3-phase synchronous motor by damper bars, the field winding is usually short circuited so that starting torque is equal to __________(a) induction motor torque plus an additional torque produced by short circuited field winding(b) induction motor torque(c) electromagnetic torque(d) reluctance torque due to rotor saliencyI have been asked this question in homework.This question is from Physical Concepts of Synchronous Machine Operation topic in section Synchronous Machines of Electrical Machines
Answer» The correct OPTION is (a) induction motor TORQUE PLUS an additional torque produced by short circuited field winding For explanation I would say: Using dampers to start the synchronous motor, it will produce induction motor torque initially ALONG with the torque due to SHORTED field winding.

Discussion

67.	To start the synchronous motor, its field winding should be __________(a) short circuited(b) kept open(c) connected to dc excitation source(d) any of the mentionedI got this question in examination.My question is based upon Physical Concepts of Synchronous Machine Operation in portion Synchronous Machines of Electrical Machines
Answer» Correct answer is (a) short circuited Easy EXPLANATION: To start the synchronous MOTOR, it is FIRST run as field EXCITATION as zero, so we short circuit them.

Discussion

68.	A poly phase synchronous motor will be used for the load of ______ over poly phase induction motor.(a) 600 kW 500 rpm(b) 600 kW 1500 rpm(c) 600 kW 3500 rpm(d) 600 kW 1200 rpmThe question was asked during a job interview.Enquiry is from Physical Concepts of Synchronous Machine Operation in portion Synchronous Machines of Electrical Machines
Answer» The correct choice is (a) 600 kW 500 rpm For explanation: A SYNCHRONOUS motor is USED at LOW speed.

Discussion

69.	The power load angle characteristic as maximum for a load angle of __________(a) 90°(b) 45°(c) more than 90°(d) 180°The question was asked in a national level competition.I want to ask this question from Physical Concepts of Synchronous Machine Operation in section Synchronous Machines of Electrical Machines
Answer» Right answer is (a) 90° Explanation: As per the PARABOLIC GRAPH, the maxima is OBTAINED at 90°.

Discussion

70.	If the 3-phase alternator has 4 poles and has synchronous speed of 120 rad/s. Then the mechanical speed in rad/sec is?(a) 60(b) 240(c) 120(d) 30This question was addressed to me in an interview.The question is from Physical Concepts of Synchronous Machine Operation topic in portion Synchronous Machines of Electrical Machines
Answer» The CORRECT OPTION is (a) 60 The BEST explanation: MECHANICAL speed = electrical speed*2/Number of POLES.

Discussion

71.	Reactive power flow in synchronous machine can be controlled by __________(a) varying field excitation(b) varying field current(c) varying field flux(d) any of the mentionedI got this question during an online interview.My doubt stems from Physical Concepts of Synchronous Machine Operation in portion Synchronous Machines of Electrical Machines
Answer» The correct choice is (d) any of the mentioned The BEST I can EXPLAIN: All the alternatives are same, VARYING the field flux matters at the end to change the reactive power in a synchronous machine.

Discussion

72.	If the synchronous machine is loaded from floating conditions, the synchronous motor begins to operate at __________(a) leading p.f(b) lagging p.f(c) unity p.f(d) zero p.fThis question was posed to me during an interview for a job.The origin of the question is Physical Concepts of Synchronous Machine Operation topic in division Synchronous Machines of Electrical Machines
Answer» The correct choice is (b) lagging p.f Easy explanation: The RESULTANT FLUX will be lagging in nature, so after LOADING it from loading it from floating, ALTERNATOR will OPERATE at lagging p.f.

Discussion

73.	If the synchronous machine is loaded from floating conditions, the alternator begins to operate at __________(a) leading p.f(b) lagging p.f(c) unity p.f(d) zero p.fI got this question in an interview.Origin of the question is Physical Concepts of Synchronous Machine Operation topic in chapter Synchronous Machines of Electrical Machines
Answer» Correct option is (a) leading p.f The explanation: The RESULTANT FLUX will be leading in nature, so after LOADING it from loading it from floating, ALTERNATOR will operate at leading p.f.

Discussion

74.	The reactive power in synchronous machine is proportional to __________(a) torque(b) excitation(c) sinϕ(d) all of the mentionedThe question was posed to me in a job interview.This intriguing question comes from Physical Concepts of Synchronous Machine Operation in section Synchronous Machines of Electrical Machines
Answer» The CORRECT ANSWER is (B) excitation To elaborate: Reactive POWER depends on the excitation of the synchronous MACHINE.

Discussion

75.	Active power in synchronous machine is proportional to __________(a) torque(b) excitation(c) sinϕ(d) all of the mentionedThis question was addressed to me in examination.The doubt is from Physical Concepts of Synchronous Machine Operation topic in chapter Synchronous Machines of Electrical Machines
Answer» The CORRECT choice is (a) TORQUE Explanation: Active POWER is proportional to the torque of the SYNCHRONOUS machine.

Discussion

76.	At steady state operation in a 3-phase synchronous generator. (where Tem is developed electromagnetic torque developed in the machine and Tpm is the prime mover torque.)(a) Tem = Tpm(b) Tem > Tpm(c) Tem < Tpm(d) can not be coupledThis question was posed to me in examination.I want to ask this question from Physical Concepts of Synchronous Machine Operation in portion Synchronous Machines of Electrical Machines
Answer» Right choice is (a) TEM = Tpm Best explanation: At steady STATE the NET TORQUE is ZERO in the machine.

Discussion

77.	If the field poles are ahead of resultant mmf, then the 3-phase synchronous machine is operating as ___________(a) generator(b) motor(c) reluctance motor(d) any of the mentionedI got this question in an interview for job.Question is from Physical Concepts of Synchronous Machine Operation in chapter Synchronous Machines of Electrical Machines
Answer» The correct answer is (a) GENERATOR The BEST I can explain: Field mmf LEADS the RESULTANT mmf so it is generator.

Discussion

78.	Floating of synchronous machine on infinite bus means ___________(a) Fa = 0 and machine neither generator nor motor(b) Fa is not zero and machine neither generator nor motor(c) Fa = 0 and machine is not excited(d) frequency is zeroI had been asked this question in an interview for job.This interesting question is from Physical Concepts of Synchronous Machine Operation in section Synchronous Machines of Electrical Machines
Answer» Right option is (a) FA = 0 and machine neither generator nor motor To elaborate: Floating means the armature FLUX is zero and it neither motoring nor generating.

Discussion

79.	If the DC excitation is suddenly dropped to 0, the three phase alternator _________(a) runs as motor(b) stops to zero speed in few seconds(c) continues to run as motor but at lower speed(d) no change in the operating conditionsThe question was posed to me during an internship interview.This intriguing question originated from Excitation Systems for Synchronous Machines topic in chapter Synchronous Machines of Electrical Machines
Answer» RIGHT choice is (a) runs as motor To explain: When the dc excitation is disconnected from the supply, it will START acting as synchronous motor as the PRIME mover will still be mechanically coupled.

Discussion

80.	The main exciter used in DC excitation is ________(a) field on stator(b) armature on stator(c) field on rotor(d) field on polesI have been asked this question by my school principal while I was bunking the class.This interesting question is from Excitation Systems for Synchronous Machines in portion Synchronous Machines of Electrical Machines
Answer» RIGHT CHOICE is (a) FIELD on STATOR The BEST explanation: The main exciter used in DC excitation is field on stator.

Discussion

81.	The brushlessexcitation and conventional DC excitation systems are comparable but one significant change is _______(a) pilot exciter is brushless permanent magnet motor(b) three phase rectifier feeds directly to main exciter(c) a three phase rectifier is fed by main exciter(d) no direct rectification is provided to the pilot exciterThis question was addressed to me by my college director while I was bunking the class.Asked question is from Excitation Systems for Synchronous Machines topic in section Synchronous Machines of Electrical Machines
Answer» Correct CHOICE is (a) PILOT exciter is brushless permanent magnet motor For EXPLANATION: The brushless excitation involves a brushless permanent motor which ACTS as an AUXILIARY exciter.

Discussion

82.	What are the main problems faced by conventional DC exciters?(a) cooling and maintainance(b) wear and tear(c) additional parasitic losses(d) all of the mentionedThis question was addressed to me in a job interview.This interesting question is from Excitation Systems for Synchronous Machines topic in portion Synchronous Machines of Electrical Machines
Answer» Correct CHOICE is (d) all of the mentioned Easiest explanation: The conventional DC EXCITERS have all the above mentioned losses which make them out DATED and least EFFICIENT.

Discussion

83.	The pilot exciter in dc exciters is ________(a) dc shunt generator feeding field winding of mains(b) universal motor(c) stepper motor feeding the field winding of mains(d) any of the mentionedI have been asked this question during an internship interview.Asked question is from Excitation Systems for Synchronous Machines topic in portion Synchronous Machines of Electrical Machines
Answer» Right option is (a) dc shunt generator feeding FIELD WINDING of mains To ELABORATE: PILOT exciter is dc shunt generator which supplies the field of MAIN winding.

Discussion

84.	In large synchronous machine, field winding is placed on ______ and ac supply on ______(a) rotor, stator(b) stator, rotor(c) armature, slots(d) pole shoes, statorI have been asked this question in an online quiz.This intriguing question comes from Excitation Systems for Synchronous Machines topic in section Synchronous Machines of Electrical Machines
Answer» The correct choice is (a) rotor, stator Easy explanation: The field winding is placed on the stator as it will carry less current while the AC supply is FED at stator as it will have to carry LARGE amount of current.

Discussion

85.	Field winding of a dc machine _________(a) always absorbs power(b) absorbs real power at lagging load(c) delivers power while behaving as generator(d) always delivers powerI got this question by my college professor while I was bunking the class.This interesting question is from Excitation Systems for Synchronous Machines topic in division Synchronous Machines of Electrical Machines
Answer» The correct option is (a) ALWAYS absorbs POWER Explanation: FIELD is always given SUPPLY from dc SYSTEM so it always absorbs power as it is necessary to produce the flux.

Discussion

86.	A 3 phase synchronous machine is _________ excited machine.(a) doubly(b) single(c) two stage(d) feedback basedThe question was asked in examination.My enquiry is from Excitation Systems for Synchronous Machines topic in chapter Synchronous Machines of Electrical Machines
Answer» CORRECT ANSWER is (a) doubly Easiest explanation: The 3 phase synchronous MACHINE has TWO excitations. Ac excitation at ARMATURE while dc excitation at field winding.

Discussion

87.	In a DC machine, z, p, Ia and a are respectively the number of conductors, number of poles, armature current and number of parallel paths. The peak value of fundamental component of armature MMF wave is ____________(a) 8/Π[(z/2p)(Ia/a)](b) 8/Π^2[(z/p)(Ia/a)](c) 4/Π[(z/2p)(Ia/a)](d) 8/Π^2[(z/p)(Ia/a)]The question was posed to me in an internship interview.Question is from MMF Produced by Distributed Windings in section Synchronous Machines of Electrical Machines
Answer» The correct OPTION is (d) 8/Π^2[(z/p)(Ia/a)] For explanation I would say: The peak value of the FUNDAMENTAL sine component FA for a DC machine is Fa=8/Π^2[(z/p)(Ia/a)] AT/pole.

Discussion

88.	A sinusoidal current sheet in a rotating electrical machine has peak value along q-axis. The peak value of sinusoidal MMF would be ___________(a) in phase with current peak(b) 90° lagging the current peak(c) 90° leading the current peak(d) may lag or lead depending upon the type of machineThe question was asked in a national level competition.Question is taken from MMF Produced by Distributed Windings in chapter Synchronous Machines of Electrical Machines
Answer» The correct ANSWER is (c) 90° leading the current peak The BEST I can explain: Sinusoidal current SHEET PRODUCES sinusoidal MMF WAVE leading by 90°.

Discussion

89.	A winding of 20 full pitched series turns, distributed over a band of 60° under each pole, carries a current of 3A. The winding produces a uniform current sheet of density (in AT’s per electrical radiangs) of ___________(a) 180/Π(b) 120/Π(c) 90/Π(d) 60/ΠThis question was addressed to me in exam.I would like to ask this question from MMF Produced by Distributed Windings topic in division Synchronous Machines of Electrical Machines
Answer» Correct option is (a) 180/Π The explanation is: UNIFORM CURRENT DENSITY J=(20∗3)/(Π/3)=180/Π.

Discussion

90.	MMF produced by one N-turn coil carrying a current i is ____________(a) rectangular of amplitude Ni/2(b) trapezoidal of amplitude Ni/2(c) rectangular of amplitude Ni(d) trapezoidal of amplitude NiThe question was asked in an interview.My question is from MMF Produced by Distributed Windings in section Synchronous Machines of Electrical Machines
Answer» The CORRECT option is (a) RECTANGULAR of amplitude Ni/2 Best EXPLANATION: The MMF variation due to one N-turn COIL is seen to be a rectangular wave of amplitude +1/2(Ni) or -1/2(Ni).

Discussion

91.	A uniformly distributed winding on the stator has three full pitched coils, each coil having N turns and each turn carrying a current i. The MMF produced by the winding is?(a) sinusoidal in waveform with an amplitude 3Ni(b) sinusoidal in waveform with an amplitude 3Ni/2(c) trapezoidal in waveform with an amplitude of 3Ni(d) trapezoidal in waveform with an amplitude of 3Ni/2This question was addressed to me by my school teacher while I was bunking the class.My question comes from MMF Produced by Distributed Windings topic in portion Synchronous Machines of Electrical Machines
Answer» The CORRECT choice is (d) trapezoidal in waveform with an AMPLITUDE of 3Ni/2 Best explanation: When the machine has more than 3 slots per POLE per phase, the steps in the MMF wave are neglected and MMF variation is taken as smooth over these slots and as a consequence, stepped MMf wave changes to trapezoidal MMF wave. The trapezoidal MMF wave amplitude = 3Ni/2.

Discussion

92.	A current sheet with sinusoidal current produces?(a) sinusoidal MMF wave lagging it by 90°(b) sinusoidal MMF wave leading it by 90°(c) trapezoidal MMF wave leading it by 90°(d) trapezoidal MMF wave lagging it by 90°I had been asked this question during a job interview.The origin of the question is MMF Produced by Distributed Windings in portion Synchronous Machines of Electrical Machines
Answer» The correct choice is (b) SINUSOIDAL MMF wave leading it by 90° Explanation: A uniform current sheet PRODUCES TRAPEZOIDAL MMF wave and sinusoidal current sheet produces sinusoidal MMF wave leading by 90°.

Discussion

93.	Which of the following statements are correct regarding the current sheet?(a) it is a thin strip of conducting material carrying the current in the dot(b) it is wrapped around stator or rotor(c) it develops MMF identical to that produced by the winding it replaces(d) any of the mentionedI have been asked this question in final exam.Asked question is from MMF Produced by Distributed Windings in section Synchronous Machines of Electrical Machines
Answer» The CORRECT option is (d) any of the mentioned To explain: The MMF PRODUCED by uniformly distributed current sheet is identical with the MMF produced by uniformly distributed WINDING. If the distributed winding in the slots is on the rotor, then the uniformly distributed current sheet would be wrapped around the rotor accordingly.

Discussion

94.	The armature MMF wave in a DC machine is ____________(a) sinusoidal and depends on the speed(b) square and independent of speed(c) triangular and depends on speed(d) triangular and independent of speedI had been asked this question in an internship interview.This is a very interesting question from MMF Produced by Distributed Windings topic in division Synchronous Machines of Electrical Machines
Answer» Correct CHOICE is (d) triangular and independent of speed The best I can explain: The ARMATURE MMF for a DC machine remains constant in amplitude and does not depend on the armature speed, also the MMF wave PRODUCED is SEEN to be a triangluar MMF wave.

Discussion

95.	Peak value of fundamental component of MMF produced by one N-turn coil carrying a current ‘i’ is ____________(a) 4/Π(Ni)(b) 2/Π(Ni)(c) 1/Π(Ni)(d) 1/2Π(Ni)I got this question in class test.I would like to ask this question from MMF Produced by Distributed Windings topic in chapter Synchronous Machines of Electrical Machines
Answer»

Discussion

96.	If the current in a coil is AC, the amplitude of MMF ___________(a) varies with time but not with space(b) varies with space but not with time(c) varies with both space and time(d) doesn’t vary with both space and timeThe question was posed to me in unit test.The doubt is from MMF Produced by Distributed Windings in division Synchronous Machines of Electrical Machines
Answer» The CORRECT CHOICE is (a) varies with time but not with SPACE Explanation: For AC in the coil, the air-gap MMF wave is time VARIANT but space invariant.

Discussion

97.	If the current in the coil is DC, then MMF doesn’t vary with ____________(a) space(b) time(c) both space and time(d) none of the mentionedThis question was posed to me in exam.This key question is from MMF Produced by Distributed Windings topic in portion Synchronous Machines of Electrical Machines
Answer» Right answer is (c) both SPACE and time To explain: If the coil current is DC, the magnitude of MMF WAVE does not vary with time and space.

Discussion

98.	A knowledge of the air gap flux distribution in a machine helps in determining the ___________(a) generated EMF waveform and its magnitude(b) electrical torque(c) winding MMF(d) both generated EMF waveform and electrical torqueI have been asked this question in a national level competition.I would like to ask this question from MMF Produced by Distributed Windings topic in portion Synchronous Machines of Electrical Machines
Answer» Right option is (d) both GENERATED EMF WAVEFORM and electrical torque The best I can explain: The winding MMF depends only on the winding arrangement and the winding CURRENT.

Discussion

99.	The winding MMF in rotating machines depends on ___________(a) winding arrangement(b) winding current(c) air gap length,slot openings etc(d) both winding arrangement and winding currentI had been asked this question in homework.My question comes from MMF Produced by Distributed Windings in division Synchronous Machines of Electrical Machines
Answer» Correct choice is (d) both WINDING ARRANGEMENT and winding current Best EXPLANATION: The winding MMF DEPENDS only on the winding arrangement and the winding current.

Discussion

100.	In all rotating electrical machine, electrical torque is developed when relative speed between stator field and rotor field is ____________(a) zero(b) equal to rotor speed(c) equal and opposite to rotor speed(d) dependent upon the type of electrical machineThe question was asked by my college professor while I was bunking the class.This intriguing question originated from Production of Torque in Non-Salient Pole Machines topic in section Synchronous Machines of Electrical Machines
Answer» Right choice is (a) zero The explanation is: If the relative speed between stator FIELD and rotor field is not zero, then the load ANGLE δr varies with time. From equation TE = -(Π/8)P^2ΦFrsinδr Nm, we can say that average torque over a COMPLETE CYCLE is zero, implies Te=0.

Discussion

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A 3 phase synchronous machine is _________ excited machine.(a) doubly(b) single(c) two stage(d) feedback basedThe question was asked in examination.My enquiry is from Excitation Systems for Synchronous Machines topic in chapter Synchronous Machines of Electrical Machines