48 + Interview Questions in Design Of Small Electrical Machines in Design Of Electrical Machines Page 1 InterviewSolution

1.	What is the plot of the magnetization curve?(a) field current in the y axis vs voltage in x axis(b) field current in the x axis vs voltage in y axis(c) armature current in the y axis vs voltage in x axis(d) armature current in the x axis vs voltage in y axisThe question was asked in an online interview.This question is from Motor Starters, Calculation of Resistance Steps & Design of Field Regulators in chapter Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» The correct choice is (b) FIELD current in the X axis vs VOLTAGE in y axis The best explanation: The magnetization curve is the curve which is USED to obtain the various values required in the design of field regulators. The curve is the plot of field current in x axis and voltage in y axis.

Discussion

2.	What is the first step in the design of the field regulators for dc motor?(a) number of sections(b) shunt field circuit resistance(c) shunt field resistance(d) resistance of stepI had been asked this question by my school principal while I was bunking the class.I want to ask this question from Motor Starters, Calculation of Resistance Steps & Design of Field Regulators in chapter Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» RIGHT OPTION is (a) number of sections Explanation: 2 machines are considered in the DESIGN of field regulators for DC machines. They are the shunt generators and shunt motor. The first STEP is the calculation of number of sections.

Discussion

3.	What is the last step involved in the design of field regulators for shunt generators?(a) calculation of the resistance of section(b) calculation of the total field circuit resistance(c) calculation of resistance of section(d) resistance to be insertedThis question was addressed to me during an online exam.My question is taken from Motor Starters, Calculation of Resistance Steps & Design of Field Regulators in chapter Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» The correct answer is (C) calculation of resistance of section For explanation: 2 machines are considered in the design of FIELD regulators for dc machines. They are the SHUNT generators and shunt motor. The LAST step is the calculation of resistance of section.

Discussion

4.	What is the second step in the design of the field regulators for dc machines?(a) calculation of the resistance of section(b) calculation of the total field circuit resistance(c) calculation of the field circuit resistance(d) resistance to be insertedThe question was posed to me at a job interview.The origin of the question is Motor Starters, Calculation of Resistance Steps & Design of Field Regulators topic in section Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» The CORRECT option is (d) resistance to be INSERTED To ELABORATE: 2 machines are considered in the design of field regulators for DC machines. They are the shunt generators and shunt motor. The second step is the calculation of the resistance to be inserted.

Discussion

5.	What is the first step in the design of the field regulators for dc machines?(a) calculation of the resistance of section(b) calculation of the total field circuit resistance(c) calculation of the field circuit resistance(d) resistance to be insertedThis question was posed to me in examination.My question comes from Motor Starters, Calculation of Resistance Steps & Design of Field Regulators topic in chapter Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» Right CHOICE is (b) calculation of the total FIELD circuit resistance The EXPLANATION: 2 machines are considered in the design of field regulators for dc machines. They are the shunt GENERATORS and shunt motor. The first step is the calculation of the field circuit resistance.

Discussion

6.	How many machines are considered for the design of field regulators for dc machines?(a) 2(b) 3(c) 4(d) 5This question was posed to me by my college professor while I was bunking the class.This key question is from Motor Starters, Calculation of Resistance Steps & Design of Field Regulators topic in chapter Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» The correct CHOICE is (a) 2 The explanation is: Two machines are considered for the DESIGN of field REGULATORS for DC machines. They are the shunt GENERATORS and shunt motor.

Discussion

7.	What is the formula of the ratio of the lower limit to upper limit of current with respect to the resistance?(a) lower limit of current / upper limit of current = motor resistance / resistance to limit the starting current(b) lower limit of current / upper limit of current = (motor resistance / resistance to limit the starting current)^1/number of resistance(c) lower limit of current / upper limit of current = (motor resistance * resistance to limit the starting current)^1/number of resistance(d) lower limit of current / upper limit of current = motor resistance * resistance to limit the starting currentThis question was addressed to me in an interview for internship.I want to ask this question from Motor Starters, Calculation of Resistance Steps & Design of Field Regulators topic in section Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» Right option is (B) lower limit of current / upper limit of current = (motor resistance / resistance to limit the STARTING current)^1/number of resistance Explanation: The motor resistance, resistance to limit the starting current and number of resistance is CALCULATED. On SUBSTITUTION the ratio of lower limit to upper limit of current is obtained.

Discussion

8.	What is the relation of the ratio of rotor current limits and the ratio of lower limit to upper limit current?(a) ratio of rotor current limits = ratio of lower limit to upper limit current(b) ratio of rotor current limits > ratio of lower limit to upper limit current(c) ratio of rotor current limits < ratio of lower limit to upper limit current(d) no relation between ratio of rotor current limits andratio of lower limit to upper limit currentI got this question in an international level competition.I want to ask this question from Motor Starters, Calculation of Resistance Steps & Design of Field Regulators topic in division Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» Right choice is (a) ratio of ROTOR current LIMITS = ratio of lower LIMIT to upper limit current Best EXPLANATION: The ratio of rotor current limits and the ratio of lower limit to upper limit current are first CALCULATED. The ratio of rotor current limits is approximately equal to the ratio of lower limit to upper limit current.

Discussion

9.	What is the concept of notching operation?(a) process of decreasing the voltage(b) process of increasing the efficiency(c) process of cutting out the resistance(d) process of adding on the resistanceI got this question in homework.My query is from Motor Starters, Calculation of Resistance Steps & Design of Field Regulators in chapter Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» CORRECT answer is (c) PROCESS of cutting out the resistance Easy explanation: The process of notching OPERATION OCCURS In the DC shunt motors. The concept of notching operation means the cutting out the resistance.

Discussion

10.	How many machines are considered in the calculation of the resistance steps?(a) 2(b) 3(c) 4(d) 5The question was posed to me during a job interview.My question is from Motor Starters, Calculation of Resistance Steps & Design of Field Regulators in chapter Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» RIGHT ANSWER is (b) 3 Explanation: There are 3 machines considered in the calculation of the resistance steps. They are starters for dc SHUNT motors, starters for dc series motors, starters for three PHASE slip RING induction motor.

Discussion

11.	What happens in the dc shunt motor when the notching process occurs?(a) flux remains constant(b) speed remains constant(c) voltage remains constant(d) current remains constantI had been asked this question in an online interview.The query is from Motor Starters, Calculation of Resistance Steps & Design of Field Regulators in portion Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» Correct option is (b) speed REMAINS constant The best explanation: Notching OPERATION means cutting out the RESISTANCE. During the process of notching speed remains constant.

Discussion

12.	What is the product of the ratio of the current and the useful flux per pole?(a) product of ratio of current anduseful per pole = (useful flux per pole due to upper limit current * upper limit current) / (useful flux per pole due to lower limit current * lower limit current)(b) product of ratio of current anduseful per pole = (useful flux per pole due to upper limit current + upper limit current) / (useful flux per pole due to lower limit current + lower limit current)(c) product of ratio of current anduseful per pole = (useful flux per pole due to upper limit current – upper limit current) / (useful flux per pole due to lower limit current – lower limit current)(d) product of ratio of current anduseful per pole = (useful flux per pole due to upper limit current * lower limit current) / (useful flux per pole due to lower limit current * upper limit current)The question was posed to me in an online quiz.My question is taken from Motor Starters, Calculation of Resistance Steps & Design of Field Regulators topic in section Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer»

Discussion

13.	What happens when the starter takes up metallic resistance?(a) voltage fluctuates from high to low(b) voltage fluctuates between fixed upper and lower limits(c) current fluctuates from high to low(d) current fluctuates between fixed upper and lower limitsI had been asked this question at a job interview.Origin of the question is Motor Starters, Calculation of Resistance Steps & Design of Field Regulators in division Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» The correct CHOICE is (d) current fluctuates between fixed upper and lower limits To elaborate: The starter actually picks up either LIQUID rheostat or metallic resistance during its operation. The starter TAKES up metallic resistance when the resistance is to be varied in steps. When taken with resistance steps, the current fluctuated between upper and lower limits.

Discussion

14.	The starter take up metallic resistance when the resistance should not be varied in steps.(a) true(b) falseThis question was addressed to me by my school teacher while I was bunking the class.My question is based upon Motor Starters, Calculation of Resistance Steps & Design of Field Regulators in chapter Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» Right CHOICE is (b) false Easy explanation: The STARTER actually picks up either liquid RHEOSTAT or metallic resistance during its operation. The starter TAKES up metallic resistance when the resistance is to be VARIED in steps.

Discussion

15.	When does the starter take up liquid rheostat?(a) when the resistance can be varied heavily(b) when the resistance can be varied gradually(c) when the resistance cannot be varied(d) when the resistance should not be variedThe question was asked during an interview for a job.I want to ask this question from Motor Starters, Calculation of Resistance Steps & Design of Field Regulators topic in section Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» Right CHOICE is (b) when the resistance can be varied gradually Easy explanation: The starter ACTUALLY PICKS up either liquid RHEOSTAT or metallic resistance during its operation. The starter takes up liquid rheostat during the situation where the resistance is gradually varied.

Discussion

16.	What is the relation of the current with the starting torque in the starter concept?(a) the starter should restrict current to prevent low starting torque(b) the starter should restrict current to produce high starting torque(c) the starter should send current to prevent low starting torque(d) the starter should send current to produce high starting torqueThe question was asked in examination.My question comes from Motor Starters, Calculation of Resistance Steps & Design of Field Regulators topic in section Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» Right answer is (d) the starter should send CURRENT to produce high starting torque The best explanation: The main FUNCTION of the starter is to prevent excessive current flow. At the same TIME it should allow current to produce good or high starting torque.

Discussion

17.	What is the function of the motor starter with respect to current?(a) to slow the low current flow(b) to prevent the low current flow(c) to allow the large current flow(d) to prevent the large current flowI got this question in an interview.This key question is from Motor Starters, Calculation of Resistance Steps & Design of Field Regulators in portion Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» CORRECT ANSWER is (d) to prevent the large CURRENT flow The best I can EXPLAIN: There are varied TYPE of starters which vary among themselves according to the function. The main function is to prevent the excessive current at the starting.

Discussion

18.	What is the work of the starter with respect to the mechanical stress?(a) to allow large mechanical stress(b) to restrict large mechanical stress(c) to allow small mechanical stress(d) to restrict small mechanical stressThis question was posed to me in class test.Asked question is from Motor Starters, Calculation of Resistance Steps & Design of Field Regulators topic in portion Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» Correct option is (b) to restrict large MECHANICAL stress Easiest explanation: The main function of the starter is to PREVENT the EXCESSIVE current at the STARTING. The other work of the starter is to restrict the large mechanical stress from acting on the MACHINES.

Discussion

19.	What is the formula of the pole arc of the universal commutator motor?(a) pole arc = ratio of armature axial length to armature diameter * pole pitch(b) pole arc = ratio of armature axial length to armature diameter + pole pitch(c) pole arc = ratio of armature axial length to armature diameter – pole pitch(d) pole arc = ratio of armature axial length to armature diameter / pole pitchThis question was posed to me in examination.I want to ask this question from Design of Small Universal Commutator Motors topic in chapter Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» Right choice is (b) pole ARC = RATIO of armature axial LENGTH to armature diameter + pole pitch Explanation: Firstly the ratio of armature axial length to armature diameter is calculated. NEXT, the pole pitch is calculated and on addition of both the TERMS the pole arc is obtained.

Discussion

20.	What is the formula for the pole pitch in the universal commutator motor?(a) pole pitch = 3.14 * diameter * 2 * no. of poles(b) pole pitch = 3.14 / diameter * 2 * no. of poles(c) pole pitch = 3.14 * diameter / 2 * no. of poles(d) pole pitch = 3.14 * diameter * 2 / no. of polesThe question was asked by my school teacher while I was bunking the class.This question is from Design of Small Universal Commutator Motors topic in chapter Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» The correct OPTION is (c) pole pitch = 3.14 * diameter / 2 * no. of poles For explanation I would SAY: The diameter and the NUMBER of poles are calculated. On SUBSTITUTION, the pole pitch of the universal commutator motor is obtained.

Discussion

21.	What is the specific magnetic loading for the motors having output less than 100 W?(a) 0.25-0.30 T(b) 0.3-0.4 T(c) 1.3-1.5 T(d) 0.25-0.35 TThe question was asked in an interview for job.The above asked question is from Design of Small Universal Commutator Motors topic in division Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» The correct answer is (d) 0.25-0.35 T The best I can explain: The SPECIFIC magnetic LOADING for the OUTPUT below 100 W is 0.25-0.35 T and the specific magnetic loading for the CONTINUOUS duty motors is 0.3-0.4 T and the specific magnetic loading for the short time duty motors is 1.3-1.5 T.

Discussion

22.	For what outputs are the 2 pole machines made use of?(a) output > 200 W(b) output < 200 W(c) output > 300 W(d) output < 300 WI have been asked this question in an interview.My doubt stems from Design of Small Universal Commutator Motors in section Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» Right ANSWER is (b) OUTPUT < 200 W Best EXPLANATION: The 2 POLE MACHINES are made use of when the output is below 200 W. The 4 pole machines are made use of when the output is above 200 W.

Discussion

23.	What is the range of the power factor for the 4 pole motors?(a) 0.6-0.85(b) 0.75-0.95(c) 0.6-0.8(d) 0.7-0.9I got this question by my school principal while I was bunking the class.Question is taken from Design of Small Universal Commutator Motors topic in section Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» The CORRECT choice is (a) 0.6-0.85 For explanation: The power factor for the 4 POLE MOTORS is 0.6-0.85. The power factor for the 2 pole motors is 0.75-0.95.

Discussion

24.	What is the value of the specific electric loading for the continuous duty motor type?(a) 8000-11000 A per m(b) 6000-9000 A per m(c) 12000-20000 A per m(d) 15000-25000 A per mThe question was asked in final exam.My doubt is from Design of Small Universal Commutator Motors in section Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» The correct option is (B) 6000-9000 A per m To elaborate: The SPECIFIC electric loading for CONTINUOUS duty motor type is 6000-9000 A per m. The specific electric loading for power RATING above 100 W but below 200 W is 8000-11000 A per m and the specific electric loading for power rating above 200 W but below 750 W is 12000-20000 A per m.

Discussion

25.	What is the range of the transformation ratio in the pole machines?(a) 0.05-0.1(b) 0.1-0.2(c) 0.1-0.25(d) 0.3-0.4I got this question in unit test.This intriguing question comes from Design of Small Universal Commutator Motors in chapter Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» Correct ANSWER is (c) 0.1-0.25 The best I can explain: The TRANSFORMATION ratio in 2 POLE motors is 0.1-0.25. The transformation ratio in the 4 pole motors is 0.05-0.1.

Discussion

26.	What is the relation of the copper loss and brush contacts with the total loss in universal commutator motors?(a) copper loss and brush contacts = total loss(b) copper loss and brush contacts = total loss/2(c) copper loss and brush contacts = total loss * 2(d) copper loss and brush contacts = total loss * 3The question was asked in an internship interview.Enquiry is from Design of Small Universal Commutator Motors topic in division Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» Right ANSWER is (b) copper LOSS and BRUSH contacts = total loss/2 Easiest explanation: The copper loss and brush contact loss is being compared with the total loss in ORDER to deduce equations. The copper loss and brush contact loss is half the total loss.

Discussion

27.	How many type of excitations does the universal commutator motors have?(a) 1(b) 2(c) 3(d) 4This question was posed to me by my college director while I was bunking the class.This key question is from Design of Small Universal Commutator Motors topic in portion Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» Right option is (B) 2 To EXPLAIN I would say: There are two kinds of excitation PRESENT for the universal commutator motors. One winding is intended to run the motor to ac SUPPLY voltage. The other winding is connected in series with the first winding when the motor is operated from DC supply voltage.

Discussion

28.	What is the relation of the copper loss and brush contacts with the total loss in small dc motors?(a) copper loss and brush contacts = 2 * total loss(b) copper loss and brush contacts = 2/3 * total loss(c) copper loss and brush contacts = 1/3 * total loss(d) copper loss and brush contacts =total lossThe question was asked by my college director while I was bunking the class.I want to ask this question from Design of Small Universal Commutator Motors in portion Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» The correct CHOICE is (B) COPPER loss and brush contacts = 2/3 * total loss Explanation: The copper loss and brush contact loss is being COMPARED with the total loss in order to deduce an equation. The copper loss and brush contact loss is 2/3 TIMES the total loss.

Discussion

29.	The number of turns of field winding in the motor must be considerably less than the number of turns in the armature winding.(a) true(b) falseI got this question at a job interview.This interesting question is from Design of Small Universal Commutator Motors in chapter Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» RIGHT answer is (a) true To explain I would SAY: The number of turns of FIELD winding in the motor must be considerably less than the number of turns in the armature winding. The SPEED of the MACHINE is irrespective of the supply.

Discussion

30.	What is the thickness of the laminations of magnetic poles?(a) 0.3-0.5 mm(b) 0.2-0.4 mm(c) 0.35-0.5 mm(d) 0.4-0.5 mmI have been asked this question in an international level competition.Question is taken from Design of Small Universal Commutator Motors topic in chapter Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» Correct ANSWER is (c) 0.35-0.5 MM To explain: The minimum VALUE of the thickness of the laminations of MAGNETIC poles is 0.35 mm. The MAXIMUM value of the thickness of the laminations of magnetic poles is 0.5 mm.

Discussion

31.	What is the material used in the lamination of the magnetic poles of small universal commutator motor?(a) copper(b) aluminium(c) gold(d) sheet steelI got this question by my school teacher while I was bunking the class.My enquiry is from Design of Small Universal Commutator Motors topic in division Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» The correct option is (d) sheet steel For EXPLANATION: UNLIKE dc motors UNIVERSAL commutator motors are having laminated POLES. The laminated poles are laminated USING the sheet steel.

Discussion

32.	What type of excitation is used in the small universal commutator motors and what type of supply is provided?(a) parallel excitation, dc supply(b) series excitation, dc or ac supply(c) series excitation, ac supply(d) parallel excitation, dc supplyThe question was posed to me in semester exam.My enquiry is from Design of Small Universal Commutator Motors topic in chapter Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» Right answer is (b) series excitation, dc or ac SUPPLY To EXPLAIN I would say: The excitation which is provided is the series excitation in the small UNIVERSAL commutator motors. The type of supply provided is dc or ac supply.

Discussion

33.	What are the applications of the small universal commutator motors?(a) industry(b) medicine(c) domestic sector(d) industry, medicine and domestic sectorI have been asked this question during an interview.I'd like to ask this question from Design of Small Universal Commutator Motors in division Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» Right CHOICE is (d) industry, MEDICINE and domestic sector Easiest explanation: Small universal commutator MOTORS have power OUTPUTS varying from few watts to hundreds of watts. They have LOTS of application in industry, medicine, domestic sector.

Discussion

34.	The active resistance of the stator winding is calculated at the temperature of 45° C.(a) true(b) falseThis question was posed to me in an interview for internship.I'd like to ask this question from Design of a Small Reluctance Motor topic in portion Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» Correct option is (b) false The EXPLANATION is: The active resistance of the STATOR WINDING determination is one of the steps in the DESIGN of stator windings. The value is calculated at the temperature of 45° C.

Discussion

35.	How many design steps are involved in the determination of the losses and efficiency?(a) 2(b) 3(c) 4(d) 5The question was asked in an online quiz.My question is taken from Design of a Small Reluctance Motor topic in portion Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» Right option is (B) 3 The explanation is: There are 3 steps INVOLVED in the DETERMINATION of the losses and efficiency. They are copper loss in stator winding, iron loss in stator steel, MECHANICAL loss in the MOTOR.

Discussion

36.	What is the formula for the slot pitch factor in design of rotors?(a) slot pitch factor = 3.14rotor diameternumber of rotor slots(b) slot pitch factor = 3.14/rotor diameternumber of rotor slots(c) slot pitch factor = 3.14rotor diameter/number of rotor slots(d) slot pitch factor = 1/3.14rotor diameternumber of rotor slotsI have been asked this question in an internship interview.This question is from Design of a Small Reluctance Motor in portion Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» CORRECT answer is (c) slot PITCH factor = 3.14*rotor DIAMETER/NUMBER of rotor slots Easy explanation: First the rotor diameter and the number of rotor slots are first calculated. On substitution the slot pitch factor can be obtained.

Discussion

37.	How many steps are involved in the design of performance parameters?(a) 6(b) 5(c) 7(d) 8I have been asked this question in an interview for internship.I need to ask this question from Design of a Small Reluctance Motor topic in section Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» Correct option is (c) 7 For explanation I would say: There are 7 steps involved in the design of the performance parameters. They are no load current, height of STEEL STATOR TEETH, weight of steel in the stator core, copper loss in the stator winding under no load, active resistance and leakage reactance, active component of no load current, starting torque of 3 phase reluctance MOTOR.

Discussion

38.	How many steps are present in the calculation of the design of stator windings?(a) 10(b) 11(c) 9(d) 12I have been asked this question in a job interview.Enquiry is from Design of a Small Reluctance Motor in section Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» The correct answer is (b) 11 Easiest EXPLANATION: There are 11 steps involved in the calculation of the design of stator windings. They are input current to motor, number of stator SLOTS, stator winding pitch, winding factor, useful FLUX, number of turns per stator winding, CROSS sectional area of the stator winding, slot area, mean length for conductor, active resistance of stator winding, specific PERMEANCE of leakage flux.

Discussion

39.	How many steps are present in the calculation of the design of rotor of reluctance motors?(a) 4(b) 5(c) 3(d) 2I had been asked this question by my college professor while I was bunking the class.This question is from Design of a Small Reluctance Motor in portion Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» Correct answer is (a) 4 To explain I would say: There are 4 STEPS involved in the design of rotor of RELUCTANCE motor. They are rotor diameter calculation, height of rotor CORE, mmf for magnetic circuit, saturation coefficient of motor.

Discussion

40.	How many steps are present in the calculation of the determination of main dimensions?(a) 5(b) 4(c) 3(d) 2This question was posed to me in examination.This is a very interesting question from Design of a Small Reluctance Motor in portion Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» CORRECT option is (a) 5 Easiest explanation: There are 5 STEPS present in the calculation of the determination of MAIN dimensions. They are electromagnetic power of reluctance motor, output coefficient, pole PITCH, pole arc, peripheral velocity.

Discussion

41.	What is the range of the constant used in the calculation of the active power of reluctance motor?(a) 0.3-0.4(b) 0.35-0.55(c) 0.40-0.50(d) 0.35-0.60The question was posed to me in an online interview.This key question is from Design of a Small Reluctance Motor in chapter Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» RIGHT choice is (b) 0.35-0.55 The best I can EXPLAIN: The minimum VALUE of the range of the constant USED in the calculation of the active POWER of reluctance motor is 0.35. The maximum value of the range of the constant used in the calculation of the active power of reluctance motor is 0.55.

Discussion

42.	How many design dimension are present in the design of the small reluctance motor?(a) 3(b) 4(c) 5(d) 6The question was asked in an interview for job.This interesting question is from Design of a Small Reluctance Motor topic in chapter Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» The correct option is (c) 5 To EXPLAIN: There are 5 design dimensions present in the design of the small reluctance motors. They are the design of the MAIN dimensions, design of STATOR windings, design of the rotor of the reluctance motor, design of performance parameters, design of losses and efficiency.

Discussion

43.	What is the angle at which the electromagnetic torque is maximum?(a) 30°(b) 45°(c) 60°(d) 90°I got this question in an internship interview.My query is from Design of a Small Reluctance Motor in division Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» RIGHT OPTION is (b) 45° Explanation: The ELECTROMAGNETIC TORQUE is maximum at the angle of 45°. The RANGE of operation of the reluctance motor lies in the range of 0-45°.

Discussion

44.	What is the range of the ratio of the direct axis reactance to the quadrature axis reactance?(a) 1.5-2.3(b) 1.6-2.7(c) 1.6-2.2(d) 1.2-2.0I got this question during an online interview.I'm obligated to ask this question of Design of a Small Reluctance Motor topic in section Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» RIGHT answer is (c) 1.6-2.2 The best I can explain: The minimum value of the RATIO of the direct axis reactance to the QUADRATURE axis reactance is 1.6. The MAXIMUM value of the ratio of the direct axis reactance to the quadrature axis reactance is 2.2.

Discussion

45.	What is the relation of the input voltage with the magnetic flux?(a) if the input voltage is constant, the magnetic flux increases(b) if the input voltage is constant, the magnetic flux decreases(c) if the input voltage is constant, the magnetic flux is constant(d) if the input voltage is constant, the magnetic flux is zeroThe question was posed to me by my school teacher while I was bunking the class.The query is from Design of a Small Reluctance Motor topic in portion Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» RIGHT answer is (c) if the input VOLTAGE is constant, the magnetic flux is constant For EXPLANATION I would say: The input voltage is GIVEN constant, which RESULTS in the constant magnetic flux. The magnetic flux is independent of the excitation.

Discussion

46.	What is the power factor in the reluctance motor and the range of efficiency?(a) leading power factor, 60-75%(b) lagging power factor, 50-75%(c) zero power factor, 55-80%(d) lagging power factor, 55-75%The question was asked during a job interview.This is a very interesting question from Design of a Small Reluctance Motor topic in chapter Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» CORRECT ANSWER is (d) lagging power FACTOR, 55-75% The BEST I can explain: The power factor in the reluctance MOTOR is lagging power factor. The efficiency of the machine is about 55-75%.

Discussion

47.	How is the reluctance motor with respect to a synchronous motor and are the field windings?(a) small synchronous motor with field windings(b) small synchronous motor without field windings(c) large synchronous motor with field windings(d) large synchronous motor without field windingsThe question was asked in an international level competition.This question is from Design of a Small Reluctance Motor in portion Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» Correct answer is (B) small SYNCHRONOUS motor without field windings For explanation: Reluctance motor is NOTHING but a SIMPLE small synchronous motor with salient pole ROTOR. They are without field windings in which the field flux is produced.

Discussion

48.	Why is the three phase reluctance motor preferred over single phase reluctance motor?(a) single phase reluctance motors have the phenomenon of hunting(b) single phase reluctance motors have the phenomenon of over voltage(c) single phase reluctance motors have high losses(d) single phase reluctance motors have low outputI had been asked this question by my college director while I was bunking the class.My doubt is from Design of a Small Reluctance Motor topic in section Design of Small Electrical Machines, Starters and Field Regulators of Design of Electrical Machines
Answer» The correct option is (a) single phase RELUCTANCE motors have the PHENOMENON of hunting Explanation: The reluctance motor is a SMALL synchronous motor with salient POLE rotor. The single phase reluctance motors have the phenomenon of hunting.

Discussion

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