97 + Interview Questions in Three Phase Induction Motor in Design Of Electrical Machines Page 1 InterviewSolution

1.	For the lower values of current, round conductors would be convenient to use.(a) true(b) falseThe question was asked by my college professor while I was bunking the class.Query is from Stator Winding in section Three Phase Induction Motor of Design of Electrical Machines
Answer» Correct choice is (a) true Easiest explanation: For lower values of current, round conductors WOULD be the most convenient to use while for higher current BARS. It should be LESS than 2 or 3 mm in diameter or ELSE it is difficult to wind.

Discussion

2.	What should be the range of current density in the stator windings?(a) 2-5 A per mm^2(b) 4-5 A per mm^2(c) 3-5 A per mm^2(d) 2-3 A per mm^2I had been asked this question in a job interview.My question is taken from Stator Winding topic in section Three Phase Induction Motor of Design of Electrical Machines
Answer» Right choice is (c) 3-5 A per mm^2 For explanation: The MINIMUM value for the CURRENT density in stator winding is 3 A per mm^2. The maximum value of the current density in the stator WINDINGS should not exceed 5 A per mm^2.

Discussion

3.	What is the formula for stator turns per phase?(a) stator turns per phase = Stator voltage per phase / 4.44 * f * maximum flux / stator winding factor(b) stator turns per phase = Stator voltage per phase * 4.44 * f * maximum flux * stator winding factor(c) stator turns per phase = Stator voltage per phase / 4.44 * f * maximum flux * stator winding factor(d) stator turns per phase = Stator voltage per phase * 4.44 * f * maximum flux / stator winding factorThe question was posed to me by my school principal while I was bunking the class.The query is from Stator Winding in portion Three Phase Induction Motor of Design of Electrical Machines
Answer» Correct option is (c) stator turns per phase = Stator voltage per phase / 4.44 * f * MAXIMUM FLUX * stator winding factor Best EXPLANATION: For the finding out of stator turns per phase, first the stator voltage per phase is OBTAINED. Next, the maximum flux is CALCULATED, then the stator winding factor is calculated.

Discussion

4.	What is the initial assumption for the value of winding factor?(a) 0.9(b) 0.95(c) 0.93(d) 0.92This question was posed to me in semester exam.Origin of the question is Stator Winding topic in division Three Phase Induction Motor of Design of Electrical Machines
Answer» Correct ANSWER is (b) 0.95 Best explanation: The winding factor may be INITIALLY assumed as 0.955. It is the value of winding factor for INFINITELY DISTRIBUTED winding with full pitch COILS.

Discussion

5.	What class does the plastic foil baked with polyamide fibres belong to?(a) Y(b) B(c) F(d) HI had been asked this question at a job interview.I'm obligated to ask this question of Stator Winding in section Three Phase Induction Motor of Design of Electrical Machines
Answer» The correct answer is (C) F Explanation: The MODERN insulating materials for diamond coils belong to classes E, B, and F. The plastic foil baked with polyamide fibres belong to CLASS F.

Discussion

6.	What is the formula for flux per pole?(a) flux per pole = average magnetic flux * pole pitch * length(b) flux per pole = average magnetic flux / pole pitch * length(c) flux per pole = average magnetic flux * pole pitch / length(d) flux per pole = average magnetic flux * pole pitch + lengthThis question was posed to me in final exam.I want to ask this question from Stator Winding topic in section Three Phase Induction Motor of Design of Electrical Machines
Answer» The correct option is (a) FLUX per pole = AVERAGE magnetic flux * pole PITCH * length The BEST I can explain: First the average magnetic flux is calculated. Then the pole pitch is calculated and then the length of the pole is calculated.

Discussion

7.	What type of winding is made use of small motors?(a) single layer mush winding(b) single layer lap winding(c) single layer wave winding(d) double layer wave windingThis question was addressed to me during an interview.This intriguing question originated from Stator Winding topic in section Three Phase Induction Motor of Design of Electrical Machines
Answer» CORRECT answer is (a) single LAYER mush winding For explanation: Small motors CONSISTING of small NUMBER of slots have a large number of turns per phase. These small motors USE single layer mush windings.

Discussion

8.	What class does the slot and phase insulation belong to?(a) B(b) Y(c) H(d) EI had been asked this question in an internship interview.This interesting question is from Stator Winding topic in section Three Phase Induction Motor of Design of Electrical Machines
Answer» Correct ANSWER is (d) E Best explanation: The modern insulating materials for diamond coils BELONG to class E, B and F. The slot and phase insulation is POLYESTER foil coated with compressed FIBRE for Class E.

Discussion

9.	How much does the addition iron losses relate with the supplied power?(a) additional iron losses = 0.5% of supplied power(b) additional iron losses = 0.6% of supplied power(c) additional iron losses = 0.8% of supplied power(d) additional iron losses = 0.9% of supplied powerThe question was posed to me during an online exam.This intriguing question comes from Losses and Efficiency topic in portion Three Phase Induction Motor of Design of Electrical Machines
Answer» The CORRECT option is (a) additional iron losses = 0.5% of SUPPLIED power The explanation is: The additional iron losses are a SMALL AMOUNT when compared with the supplied power. They are 0.5% of the supplied power.

Discussion

10.	What type of winding is generally used for the stators?(a) double layer wave winding(b) double layer lap winding(c) single layer wave winding(d) single layer lap windingI have been asked this question by my college professor while I was bunking the class.My enquiry is from Stator Winding topic in chapter Three Phase Induction Motor of Design of Electrical Machines
Answer» Right OPTION is (B) double layer lap WINDING To ELABORATE: The double layer wave winding is generally used for stators. The wave winding is with diamond coils is used for stators.

Discussion

11.	How many types are the additional losses in iron classified into?(a) 2(b) 3(c) 4(d) 5This question was addressed to me in an interview.I need to ask this question from Losses and Efficiency topic in chapter Three Phase Induction Motor of Design of Electrical Machines
Answer» CORRECT ANSWER is (a) 2 For explanation I would say: The additional iron losses are classified into 2 TYPES. They are i) pulsation losses and ii) surface losses.

Discussion

12.	What should be the maximum permissible level for frequency in normal operating conditions?(a) < 2 Hz(b) > 3 Hz(c) < 4 Hz(d) > 3 HzThe question was asked in quiz.Question is taken from Losses and Efficiency in division Three Phase Induction Motor of Design of Electrical Machines
Answer» Right ANSWER is (b) > 3 HZ The explanation: The normal condition operation depends UPON the FREQUENCY levels in the machine. It should not exceed 3 Hz.

Discussion

13.	The pulsation losses are caused by the direct axis pulsation of magnetic flux.(a) true(b) falseThis question was posed to me in exam.The question is from Losses and Efficiency topic in portion Three Phase Induction Motor of Design of Electrical Machines
Answer» Right option is (a) true To ELABORATE: The pulsation losses are one type of ADDITIONAL iron losses PRODUCED. They are produced by the direct axis pulsation of magnetic flux due to the variation of permeance caused by the continuous change in mutual POSITIONS of rotor and stator teeth during rotation of rotor.

Discussion

14.	What is the use of skin effects in the induction motor?(a) it helps in improving the efficiency(b) it helps in improving the stopping characteristics(c) it helps in improving the starting characteristics(d) it helps in improving the running characteristicsThe question was asked during an interview.Origin of the question is Losses and Efficiency in portion Three Phase Induction Motor of Design of Electrical Machines
Answer» RIGHT answer is (c) it helps in improving the starting characteristics The explanation: The SKIN EFFECT phenomenon is observed in STATOR and rotor windings in the INDUCTION motor. The effect may be used for improving starting characteristics.

Discussion

15.	What factor does the additional copper losses depend upon?(a) skin effect(b) mmf harmonics(c) machine design(d) mmf harmonics and skin effectThis question was addressed to me by my college director while I was bunking the class.Origin of the question is Losses and Efficiency topic in division Three Phase Induction Motor of Design of Electrical Machines
Answer» Correct OPTION is (d) MMF harmonics and skin effect To explain: With a sinusoidal voltage impressed over the terminal of the MOTOR, the additional copper losses are caused. They are caused DUE to the higher order mmf harmonics and skin effect.

Discussion

16.	How can the additional losses be decreased in the induction motor?(a) chording the stator winding(b) skewing the rotor(c) having a proper slot combination(d) chording the stator winding, skewing the rotor, having a proper slot combinationThis question was addressed to me in an international level competition.This intriguing question comes from Losses and Efficiency in section Three Phase Induction Motor of Design of Electrical Machines
Answer» Correct choice is (d) chording the stator winding, skewing the rotor, having a proper SLOT combination Best EXPLANATION: There are 3 methods to DECREASE the ADDITIONAL losses in induction MOTOR. They are chording the stator winding, skewing the rotor, having a proper slot combination.

Discussion

17.	The additional losses owing to the higher order mmf harmonics occur mainly in windings of squirrel cage rotor.(a) true(b) falseThe question was posed to me in my homework.Query is from Losses and Efficiency topic in chapter Three Phase Induction Motor of Design of Electrical Machines
Answer» The correct answer is (a) true The best I can explain: The ADDITIONAL losses are depending on the HIGHER order MMF harmonics and skin effect. The losses occur MAINLY in the squirrel cage rotor.

Discussion

18.	What is the formula for efficiency at full load?(a) efficiency at full load = output / output + losses(b) efficiency at full load = output / output – losses(c) efficiency at full load = output / output * losses(d) efficiency at full load = output * output + lossesThe question was posed to me during a job interview.The above asked question is from Losses and Efficiency in division Three Phase Induction Motor of Design of Electrical Machines
Answer» Right option is (a) EFFICIENCY at full LOAD = output / output + losses To elaborate: First the various losses are calculated for the machine. Then the output OBTAINED is observed and the substitution of the values in the formula GIVES the efficiency at full load.

Discussion

19.	How many losses are present in induction motors?(a) 4(b) 3(c) 5(d) 2The question was posed to me in examination.My question is from Losses and Efficiency topic in chapter Three Phase Induction Motor of Design of Electrical Machines
Answer» Right answer is (c) 5 To EXPLAIN I would say: There are 5 losses present in the induction motor. They are i) STATOR copper losses, ii) Rotor copper losses, iii) Stator iron losses, iv) FRICTION and winding losses, v) ADDITIONAL losses.

Discussion

20.	How many types of additional losses are present?(a) 1(b) 4(c) 2(d) 3I got this question in an interview.My doubt stems from Losses and Efficiency in section Three Phase Induction Motor of Design of Electrical Machines
Answer» Correct choice is (c) 2 To elaborate: The ADDITIONAL LOSSES are DIVIDED into 2 types. They are i) Additional COPPER loss ii) Additional IRON losses.

Discussion

21.	The magnetizing current decreases as the number of poles is decreased.(a) true(b) falseI have been asked this question during a job interview.Question is from Dispersion Coefficient in division Three Phase Induction Motor of Design of Electrical Machines
Answer» Correct OPTION is (a) true To explain I WOULD say: As the NUMBER of poles is reduced the magnetizing current is reduced. As the magnetizing current is reduced, the dispersion COEFFICIENT decreases and the power factor increases.

Discussion

22.	What is the relation between maximum power and the number of poles?(a) maximum power factor is directly proportional to the number of poles(b) maximum power factor is directly proportional to the square of the number of poles(c) maximum power factor is indirectly proportional to the number of poles(d) maximum power factor is indirectly proportional to the square of the number of polesThe question was asked during a job interview.Asked question is from Dispersion Coefficient topic in portion Three Phase Induction Motor of Design of Electrical Machines
Answer» The correct CHOICE is (c) MAXIMUM power factor is indirectly proportional to the number of poles Explanation: SHORT circuit CURRENT is indirectly proportional to the number of poles. The short circuit current increases the dispersion COEFFICIENT. As the dispersion coefficient increases, the maximum power factor decreases.

Discussion

23.	What is the relation between the ideal short circuit current and the number of poles?(a) short circuit current is directly proportional to the number of poles(b) short circuit current is directly proportional to the square of the number of poles(c) short circuit current is indirectly proportional to the number of poles(d) short circuit current is indirectly proportional to the square of the number of polesI had been asked this question in an interview for internship.My doubt is from Dispersion Coefficient topic in portion Three Phase Induction Motor of Design of Electrical Machines
Answer» Right choice is (C) short circuit CURRENT is indirectly proportional to the number of POLES Easy explanation: The ideal short circuit current is indirectly proportional to the number of poles. As the number of poles increases, the ideal short circuit current decreases.

Discussion

24.	What is the relation between the overload capacity and magnetizing current?(a) overload capacity is directly proportional to the magnetizing current(b) overload capacity is indirectly proportional to the magnetizing current(c) overload capacity is directly proportional to the square of the magnetizing current(d) overload capacity is indirectly proportional to the square of the magnetizing currentI have been asked this question in unit test.The query is from Dispersion Coefficient in chapter Three Phase Induction Motor of Design of Electrical Machines
Answer» CORRECT option is (a) overload CAPACITY is directly proportional to the magnetizing current To EXPLAIN: Overload capacity is directly proportional to the magnetizing current. Overload capacity INCREASES the magnetizing current and this increases the dispersion coefficient and this gives a poor power factor.

Discussion

25.	What is the relation between the overload capacity and dispersion coefficient?(a) overload capacity is directly proportional to the dispersion coefficient(b) overload capacity is indirectly proportional to the dispersion coefficient(c) overload capacity is directly proportional to the square of the dispersion coefficient(d) overload capacity is indirectly proportional to the square of the dispersion coefficientThe question was asked in final exam.The doubt is from Dispersion Coefficient in chapter Three Phase Induction Motor of Design of Electrical Machines
Answer» The CORRECT ANSWER is (b) OVERLOAD capacity is indirectly PROPORTIONAL to the dispersion coefficient The explanation is: Overload capacity is indirectly proportional to the dispersion coefficient. The overload capacity of induction motors decreases with an increase in the dispersion coefficient.

Discussion

26.	What is the relation between the dispersion coefficient and maximum power factor?(a) dispersion coefficient is directly proportional to the power factor(b) dispersion coefficient is indirectly proportional to the power factor(c) dispersion coefficient is directly proportional to the square of the power factor(d) dispersion coefficient is indirectly proportional to the square of the power factorThis question was posed to me during an interview.This intriguing question originated from Dispersion Coefficient in portion Three Phase Induction Motor of Design of Electrical Machines
Answer» Correct option is (B) dispersion coefficient is indirectly proportional to the power factor Best EXPLANATION: The dispersion coefficient is indirectly proportional to the maximum power factor. As the dispersion coefficient INCREASES, the power factor reduces DRASTICALLY.

Discussion

27.	What is the value of the no. of poles for obtaining a dispersion coefficient = 0.5?(a) 5(b) 7(c) 10(d) 6The question was posed to me at a job interview.My doubt stems from Dispersion Coefficient topic in chapter Three Phase Induction Motor of Design of Electrical Machines
Answer» Right answer is (d) 6 The EXPLANATION is: The machines with 6 poles can RESULT in a dispersion COEFFICIENT of 0.5. The dispersion coefficient of 0.5 can be obtained for 2 pole and 4 pole machines also.

Discussion

28.	What is the relation between the power factor and the air gap length?(a) small air gap length, dispersion coefficient increases, good power factor(b) small air gap length, dispersion coefficient decreases, bad power factor(c) small air gap length, dispersion coefficient increases, bad power factor(d) small air gap length, dispersion coefficient decreases, good power factorI got this question by my college director while I was bunking the class.The question is from Dispersion Coefficient topic in division Three Phase Induction Motor of Design of Electrical Machines
Answer» Right choice is (d) SMALL air gap length, dispersion coefficient decreases, good POWER FACTOR Explanation: If the air gap length is small, the dispersion coefficient decreases. As the dispersion coefficient decreases, the power factor INCREASES.

Discussion

29.	What is the relation between the number of poles and pole pitch with power factor?(a) number of poles increases, pole pitch increases, bad power factor(b) number of poles increases, pole pitch decreases, good power factor(c) number of poles increases, pole pitch decreases, good power factor(d) number of poles increases, pole pitch increases, bad power factorI had been asked this question during an interview.Question is taken from Dispersion Coefficient in chapter Three Phase Induction Motor of Design of Electrical Machines
Answer» Correct option is (c) NUMBER of poles increases, POLE pitch decreases, good POWER FACTOR Explanation: As the number of poles increases, the pole pitch decreases and the number of slots per pole per phase also decreases. This increases the DISPERSION coefficient and it leads to poor power factor.

Discussion

30.	The increase in number of poles, the dispersion coefficient increases and this gives a low power factor.(a) true(b) falseI had been asked this question in an interview for job.Question is taken from Dispersion Coefficient topic in chapter Three Phase Induction Motor of Design of Electrical Machines
Answer» The CORRECT answer is (a) true For explanation I WOULD say: The increase in number of poles INCREASES the dispersion coefficient. The increases in dispersion coefficient gives a low POWER factor.

Discussion

31.	What is the formula for dispersion coefficient?(a) dispersion coefficient = 0.838 * 10^6 * 3.14 / air gap length * effective specific permeance / pole pitch * (window space factor)^2 * number of slots per pole per phase(b) dispersion coefficient = 0.838 * 10^6 * 3.14 * air gap length / effective specific permeance / pole pitch * (window space factor)^2 * number of slots per pole per phase(c) dispersion coefficient = 0.838 * 10^6 * 3.14 * air gap length * effective specific permeance * pole pitch * (window space factor)^2 * number of slots per pole per phase(d) dispersion coefficient = 0.838 * 10^6 * 3.14 * air gap length * effective specific permeance / pole pitch * (window space factor)^2 * number of slots per pole per phaseI have been asked this question in a job interview.I need to ask this question from Dispersion Coefficient in portion Three Phase Induction Motor of Design of Electrical Machines
Answer» Correct choice is (d) dispersion coefficient = 0.838 * 10^6 * 3.14 * air GAP length * EFFECTIVE SPECIFIC permeance / pole pitch * (window space factor)^2 * number of slots per pole per PHASE Best explanation: For the CALCULATION of dispersion coefficient, first the air gap length, effective specific permeance is calculated. Next the pole pitch, window space factor and the number of slots per pole per phase.

Discussion

32.	What is the relation between the leakage current and power factor?(a) leakage current is directly proportional to the power factor(b) leakage current is indirectly proportional to the power factor(c) leakage current is directly proportional to the square of the power factor(d) leakage current is indirectly proportional to the square of the power factorI had been asked this question by my college director while I was bunking the class.This question is from Dispersion Coefficient in chapter Three Phase Induction Motor of Design of Electrical Machines
Answer» The correct option is (b) leakage current is INDIRECTLY PROPORTIONAL to the power FACTOR The best explanation: Leakage current is indirectly proportional to the power factor. A SMALL leakage current means a very GOOD power factor.

Discussion

33.	How many factors influence the power factor of an induction motor?(a) 3(b) 2(c) 1(d) 4I had been asked this question in an interview for job.I'm obligated to ask this question of Dispersion Coefficient in chapter Three Phase Induction Motor of Design of Electrical Machines
Answer» CORRECT CHOICE is (B) 2 Explanation: There are 2 factors which influence the power factor of an induction MOTOR. They are magnetizing current and ideal SHORT circuit current.

Discussion

34.	The no load power factor is the ratio of full load current to no load current.(a) true(b) falseI have been asked this question in class test.Question is taken from No Load Current in division Three Phase Induction Motor of Design of Electrical Machines
Answer» CORRECT option is (a) true To explain I would say: For obtaining the no load power FACTOR FIRST the no load current value is obtained. Then the full load current value is obtained and the RATIO gives the no load power factor.

Discussion

35.	What is the relation between the magnetizing current and power factor?(a) magnetizing current is directly proportional to the power factor(b) magnetizing current is indirectly proportional to the power factor(c) magnetizing current is directly proportional to the square of the power factor(d) magnetizing current is indirectly proportional to the square of the power factorI had been asked this question by my school principal while I was bunking the class.This interesting question is from Dispersion Coefficient topic in section Three Phase Induction Motor of Design of Electrical Machines
Answer» Correct answer is (a) magnetizing current is DIRECTLY proportional to the power FACTOR Easiest explanation: Magnetizing current is indirectly proportional to the power factor. As the magnetizing current is LARGE, the power factor is poor.

Discussion

36.	What is the no load current percent of the full load current for the output of 37 KW?(a) 50%(b) 30%(c) 27%(d) 67%This question was posed to me in unit test.Enquiry is from No Load Current in division Three Phase Induction Motor of Design of Electrical Machines
Answer» Right ANSWER is (b) 30% To explain: For output of 0.75 kW, the no LOAD current is 50% of full load current. For output of 75 kW and above, the no load current is 27% of the full load current.

Discussion

37.	What is the no load current percent of the full load current for the output of 0.75 KW?(a) 50%(b) 40%(c) 33%(d) 90%This question was addressed to me in an internship interview.I want to ask this question from No Load Current topic in division Three Phase Induction Motor of Design of Electrical Machines
Answer» Right CHOICE is (a) 50% The best I can explain: For OUTPUT of 3 KW, the no load current is 40% of FULL load current. For output of 15 kW, the no load current is 33% of the full load current.

Discussion

38.	What is the formula for the magnetizing current per phase?(a) magnetizing current per phase = (0.427 * no. of poles * total magnetizing mmf per pole) / stator winding factor * no of turns of stator slots(b) magnetizing current per phase = (0.427 / no. of poles * total magnetizing mmf per pole) / stator winding factor * no of turns of stator slots(c) magnetizing current per phase = (0.427 * no. of poles / total magnetizing mmf per pole) / stator winding factor * no of turns of stator slots(d) magnetizing current per phase = (0.427 * no. of poles * total magnetizing mmf per pole) * stator winding factor * no of turns of stator slotsI got this question in examination.Question is from No Load Current topic in portion Three Phase Induction Motor of Design of Electrical Machines
Answer» Correct CHOICE is (a) magnetizing CURRENT per phase = (0.427 * no. of poles * TOTAL magnetizing MMF per pole) / stator winding factor * no of turns of stator slots The best I can explain: FIRSTLY the total magnetizing mmf per pole is calculated. Then the no of poles and the stator winding factor is calculated. Next the no. of turns of stator slots is calculated and the magnetizing current per phase can be obtained.

Discussion

39.	What is the formula for the mmf required for stator teeth?(a) mmf required for stator teeth = mmf per metre + depth of stator slots(b) mmf required for stator teeth = mmf per metre * depth of stator slots(c) mmf required for stator teeth = mmf per metre / depth of stator slots(d) mmf required for stator teeth = mmf per metre – depth of stator slotsI have been asked this question during an online exam.My doubt stems from No Load Current in section Three Phase Induction Motor of Design of Electrical Machines
Answer» Correct option is (b) MMF required for stator teeth = mmf PER metre * depth of stator slots To ELABORATE: First the mmf per meter is obtained SEPARATELY from its design equation. Then the depth of the stator slots is obtained and the product of both GIVES mmf required for stator teeth.

Discussion

40.	At what angle with respect to the interpolar axis does the flux tube gives a good approximation?(a) 30°(b) 45°(c) 60°(d) 90°The question was posed to me in quiz.I'd like to ask this question from No Load Current topic in portion Three Phase Induction Motor of Design of Electrical Machines
Answer» Right answer is (c) 60° To EXPLAIN: The flux tube crossing the air gap at 60° from the interpolar AXIS will always GIVE a good approximation. The calculation of the magnetizing MMF should be based upon the value of the flux DENSITY at 60° from the interpolar axis.

Discussion

41.	What is the formula for mmf for air gap?(a) mmf for air gap = 800000 * air gap flux density * air gap factor * length of air gap(b) mmf for air gap = 800000 / air gap flux density * air gap factor * length of air gap(c) mmf for air gap = 800000 * air gap flux density / air gap factor * length of air gap(d) mmf for air gap = 800000 * air gap flux density * air gap factor / length of air gapThis question was addressed to me during an internship interview.This interesting question is from No Load Current in section Three Phase Induction Motor of Design of Electrical Machines
Answer» Correct choice is (a) MMF for air gap = 800000 * air gap flux density * air gap factor * length of air gap The best explanation: For CALCULATING the mmf for air gap, the air gap flux density is FIRST calculated. NEXT the air gap factor is calculated along with the length of air gap.

Discussion

42.	The flux is distributed sinusoidally and the mmf varies sinusoidally in a DC Machine.(a) true(b) falseThe question was posed to me during an online interview.My question comes from No Load Current in division Three Phase Induction Motor of Design of Electrical Machines
Answer» The CORRECT option is (b) false Best explanation: In a DC MACHINE, the flux is assumed to be uniform over any cross section and the same mmf for all the PATHS. But in an induction machine, the flux is DISTRIBUTED sinusoidally, and the mmf varies sinusoidally.

Discussion

43.	When maximum values of the design factors are considered, what is the relation between flux and the magnetizing current?(a) flux is directly proportional to the magnetizing current(b) flux is indirectly proportional to the magnetizing current(c) flux is directly proportional to square of the magnetizing current(d) flux is indirectly proportional to square of the magnetizing currentThis question was addressed to me during an interview for a job.The origin of the question is No Load Current topic in chapter Three Phase Induction Motor of Design of Electrical Machines
Answer» Right answer is (B) flux is indirectly proportional to the magnetizing CURRENT Best EXPLANATION: The flux value is indirectly proportional to the magnetizing current. The flux is too small or rather the magnetizing current BECOMES HIGH.

Discussion

44.	What factors does the value of magnetizing current depend on?(a) flux tube(b) output power(c) mean mmf(d) mean mmf and flux tubeThis question was addressed to me in examination.Question is from No Load Current topic in division Three Phase Induction Motor of Design of Electrical Machines
Answer» Correct OPTION is (d) mean mmf and flux tube Easiest explanation: If the PERMEABILITY of IRON were constant this would CAUSE no difficulty. The value of MAGNETIZING current would be accurately obtained by considering the mean mmf and the flux tube where this mean occurs.

Discussion

45.	How many parts does the flux produced by stator mmf passes through?(a) 3(b) 4(c) 5(d) 6The question was posed to me at a job interview.My question is taken from No Load Current in portion Three Phase Induction Motor of Design of Electrical Machines
Answer» The correct choice is (c) 5 The explanation: The FLUX produced by stator mmf passes through 5 parts. They are AIR GAP, ROTOR teeth, rotor core, stator teeth, stator core.

Discussion

46.	How is the Magnetizing component with respect to the voltage?(a) the magnetizing component is in phase with the voltage(b) the magnetizing component is 90° leading the voltage(c) the magnetizing component is 90° lagging the voltage(d) the magnetizing component is 90° out of phase with the voltageThis question was posed to me during a job interview.The query is from No Load Current topic in division Three Phase Induction Motor of Design of Electrical Machines
Answer» CORRECT option is (d) the magnetizing component is 90° out of phase with the voltage The BEST I can explain: The magnetizing CURRENT component is 90° out of phase with the voltage. The loss component is in phase with the voltage.

Discussion

47.	How many components does the no load current characteristics comprise of?(a) 2(b) 3(c) 4(d) 1This question was addressed to me in examination.My question is based upon No Load Current topic in section Three Phase Induction Motor of Design of Electrical Machines
Answer» Correct answer is (a) 2 To explain: There are 2 MAIN components under the no LOAD CURRENT. They are MAGNETIZING current and Loss COMPONENT of current.

Discussion

48.	How many methods are present to obtain all the machine performance characteristics?(a) 3(b) 2(c) 1(d) 4I had been asked this question in examination.The above asked question is from No Load Current in chapter Three Phase Induction Motor of Design of Electrical Machines
Answer» Correct option is (B) 2 Easy explanation: There are 2 methods in obtaining all the open circuit characteristics. They are no LOAD characteristics and SHORT circuit characteristics.

Discussion

49.	What type of winding is made use of for the large motors?(a) mush windings(b) bar type windings(c) cross windings(d) rounded windingsThis question was posed to me in examination.I'm obligated to ask this question of Design of Wound Rotor in portion Three Phase Induction Motor of Design of Electrical Machines
Answer» The correct answer is (b) BAR TYPE windings Easy explanation: For the small motors mush windings are made USE of. For the large motors, a double LAYER bar type winding is made use of.

Discussion

50.	What type of winding is made use of for the small motors?(a) mush windings(b) cross windings(c) interconnected windings(d) rounded windingsThe question was posed to me during an interview for a job.I'd like to ask this question from Design of Wound Rotor topic in chapter Three Phase Induction Motor of Design of Electrical Machines
Answer» Correct OPTION is (a) mush WINDINGS Easiest explanation: For the small MOTORS, it is a normal practice to USE mush windings. The mush windings should be housed in the semi-closed slots.

Discussion

Explore topic-wise InterviewSolutions in .

For the lower values of current, round conductors would be convenient to use.(a) true(b) falseThe question was asked by my college professor while I was bunking the class.Query is from Stator Winding in section Three Phase Induction Motor of Design of Electrical Machines

What is the initial assumption for the value of winding factor?(a) 0.9(b) 0.95(c) 0.93(d) 0.92This question was posed to me in semester exam.Origin of the question is Stator Winding topic in division Three Phase Induction Motor of Design of Electrical Machines

What class does the plastic foil baked with polyamide fibres belong to?(a) Y(b) B(c) F(d) HI had been asked this question at a job interview.I'm obligated to ask this question of Stator Winding in section Three Phase Induction Motor of Design of Electrical Machines

What class does the slot and phase insulation belong to?(a) B(b) Y(c) H(d) EI had been asked this question in an internship interview.This interesting question is from Stator Winding topic in section Three Phase Induction Motor of Design of Electrical Machines

How many types are the additional losses in iron classified into?(a) 2(b) 3(c) 4(d) 5This question was addressed to me in an interview.I need to ask this question from Losses and Efficiency topic in chapter Three Phase Induction Motor of Design of Electrical Machines

What should be the maximum permissible level for frequency in normal operating conditions?(a) < 2 Hz(b) > 3 Hz(c) < 4 Hz(d) > 3 HzThe question was asked in quiz.Question is taken from Losses and Efficiency in division Three Phase Induction Motor of Design of Electrical Machines

The pulsation losses are caused by the direct axis pulsation of magnetic flux.(a) true(b) falseThis question was posed to me in exam.The question is from Losses and Efficiency topic in portion Three Phase Induction Motor of Design of Electrical Machines

The additional losses owing to the higher order mmf harmonics occur mainly in windings of squirrel cage rotor.(a) true(b) falseThe question was posed to me in my homework.Query is from Losses and Efficiency topic in chapter Three Phase Induction Motor of Design of Electrical Machines

How many losses are present in induction motors?(a) 4(b) 3(c) 5(d) 2The question was posed to me in examination.My question is from Losses and Efficiency topic in chapter Three Phase Induction Motor of Design of Electrical Machines

How many types of additional losses are present?(a) 1(b) 4(c) 2(d) 3I got this question in an interview.My doubt stems from Losses and Efficiency in section Three Phase Induction Motor of Design of Electrical Machines

The magnetizing current decreases as the number of poles is decreased.(a) true(b) falseI have been asked this question during a job interview.Question is from Dispersion Coefficient in division Three Phase Induction Motor of Design of Electrical Machines

What is the value of the no. of poles for obtaining a dispersion coefficient = 0.5?(a) 5(b) 7(c) 10(d) 6The question was posed to me at a job interview.My doubt stems from Dispersion Coefficient topic in chapter Three Phase Induction Motor of Design of Electrical Machines

The increase in number of poles, the dispersion coefficient increases and this gives a low power factor.(a) true(b) falseI had been asked this question in an interview for job.Question is taken from Dispersion Coefficient topic in chapter Three Phase Induction Motor of Design of Electrical Machines

How many factors influence the power factor of an induction motor?(a) 3(b) 2(c) 1(d) 4I had been asked this question in an interview for job.I'm obligated to ask this question of Dispersion Coefficient in chapter Three Phase Induction Motor of Design of Electrical Machines

The no load power factor is the ratio of full load current to no load current.(a) true(b) falseI have been asked this question in class test.Question is taken from No Load Current in division Three Phase Induction Motor of Design of Electrical Machines

What is the no load current percent of the full load current for the output of 37 KW?(a) 50%(b) 30%(c) 27%(d) 67%This question was posed to me in unit test.Enquiry is from No Load Current in division Three Phase Induction Motor of Design of Electrical Machines

At what angle with respect to the interpolar axis does the flux tube gives a good approximation?(a) 30°(b) 45°(c) 60°(d) 90°The question was posed to me in quiz.I'd like to ask this question from No Load Current topic in portion Three Phase Induction Motor of Design of Electrical Machines

The flux is distributed sinusoidally and the mmf varies sinusoidally in a DC Machine.(a) true(b) falseThe question was posed to me during an online interview.My question comes from No Load Current in division Three Phase Induction Motor of Design of Electrical Machines

What factors does the value of magnetizing current depend on?(a) flux tube(b) output power(c) mean mmf(d) mean mmf and flux tubeThis question was addressed to me in examination.Question is from No Load Current topic in division Three Phase Induction Motor of Design of Electrical Machines

How many parts does the flux produced by stator mmf passes through?(a) 3(b) 4(c) 5(d) 6The question was posed to me at a job interview.My question is taken from No Load Current in portion Three Phase Induction Motor of Design of Electrical Machines

How many components does the no load current characteristics comprise of?(a) 2(b) 3(c) 4(d) 1This question was addressed to me in examination.My question is based upon No Load Current topic in section Three Phase Induction Motor of Design of Electrical Machines

How many methods are present to obtain all the machine performance characteristics?(a) 3(b) 2(c) 1(d) 4I had been asked this question in examination.The above asked question is from No Load Current in chapter Three Phase Induction Motor of Design of Electrical Machines