84 + Interview Questions in Rating And Heating Of Motors in Electric Drives Page 1 InterviewSolution

1.	Electric motors are placed in __________ to protect them from dust and contamination.(a) Enclosures(b) Open environment(c) Moisturizing environment(d) Hot environmentI have been asked this question by my school teacher while I was bunking the class.The question is from Motors Rating and Heating in section Rating and Heating of Motors of Electric Drives
Answer» Correct answer is (a) Enclosures To explain: Electric motors are placed in enclosures to protect them from dust and contamination. There are seven most COMMON types of enclosures. For example- OPEN DRIP PROOF.

Discussion

2.	Second lowest order harmonic present in 3-Φ fully controlled rectifier is __________(a) 5^th(b) 7^th(c) 3^rd(d) 2^ndI got this question during an interview.This question is from Motors Rating and Heating topic in chapter Rating and Heating of Motors of Electric Drives
Answer» Right ANSWER is (b) 7^th The BEST explanation: Only 6k±1 order harmonics are present in 3-Φ fully controlled rectifier. The second lowest order harmonic is 7^th harmonic for k=1. Third order harmonics are ABSENT in 3-Φ fully controlled rectifier.

Discussion

3.	Full form of VRF.(a) Voltage ripple factor(b) Voltage revert factor(c) Volume ripple factor(d) Volume revert factorI had been asked this question during an online interview.I would like to ask this question from Motors Rating and Heating in section Rating and Heating of Motors of Electric Drives
Answer» Correct answer is (a) VOLTAGE ripple FACTOR Best EXPLANATION: Voltage ripple factor measures the HARMONICS on the DC side of the converter. The value of voltage ripple factor is √F.F^2-1. The form factor is Vr.m.s÷Vavg.

Discussion

4.	Calculate the value of THD if the distortion factor is .8.(a) 76 %(b) 75 %(c) 74 %(d) 73 %I got this question in an interview for job.My doubt stems from Motors Rating and Heating in division Rating and Heating of Motors of Electric Drives
Answer» The CORRECT choice is (b) 75 % The best EXPLANATION: THD measures the harmonics DISTORTION in the signal. The value of THD is √(1÷D)^2-1=75 %. The value of the distortion factor is Ior.m.s÷IR.m.s.

Discussion

5.	Calculate the value of Voltage ripple factor if the Form factor is 1.1.(a) 45.8 %(b) 46.2 %(c) 47.5 %(d) 49.9 %The question was posed to me in my homework.I need to ask this question from Motors Rating and Heating in portion Rating and Heating of Motors of Electric Drives
Answer» The CORRECT option is (a) 45.8 % For explanation: VOLTAGE ripple factor MEASURES the harmonics on the DC side of the converter. The VALUE of voltage ripple factor is √F.F^2-1=45.8 %. The form factor is Vr.m.s÷Vavg.

Discussion

6.	Calculate the compensator rating required for a sec(Φ)=1.(a) 0.64 P.U(b) 0.21 P.U(c) 0.57 P.U(d) 0 P.UI have been asked this question in an interview for internship.This question is from Motors Rating and Heating topic in section Rating and Heating of Motors of Electric Drives
Answer» The correct choice is (d) 0 P.U For EXPLANATION: The compensator RATING can be calculated using the relation QP.U=√1-cos^2(∅)=0. This PER unit value VAR compensator is required to improve the POWER factor of the system.

Discussion

7.	Full form of THD is ____________(a) Total harmonic diverter(b) Total harmonic digital(c) Total harmonic distortion(d) Total harmonic discreteI had been asked this question in an internship interview.Enquiry is from Motors Rating and Heating in portion Rating and Heating of Motors of Electric Drives
Answer» Right option is (c) Total HARMONIC distortion For EXPLANATION I would SAY: THD stands for total harmonic distortion. It measures the harmonic distortion in the signal. According to IEEE-1992, only 5% of THD is VALID.

Discussion

8.	The most common cause of motor failure is ____________(a) Overloading(b) Low resistance(c) Contamination(d) Over-HeatingI had been asked this question in semester exam.The above asked question is from Motors Rating and Heating topic in division Rating and Heating of Motors of Electric Drives
Answer» Correct answer is (b) Low RESISTANCE The EXPLANATION: The most common cause of motor failure is low resistance. Overheating, CORROSION can damage the INSULATION of the windings which leads to low resistance.

Discussion

9.	Full form of IDMT is _________(a) Inverse definite minimum time(b) Inverter definite minimum time(c) Inverter definite maximum time(d) Insert definite minimum timeI got this question by my college professor while I was bunking the class.I want to ask this question from Motors Rating and Heating in portion Rating and Heating of Motors of Electric Drives
Answer» The CORRECT choice is (a) Inverse definite MINIMUM time For explanation I WOULD SAY: IDMT stands for Inverse definite minimum time over-current relay. It has both the CHARACTERISTICS of inverse over-current and definite time over-current relay.

Discussion

10.	Overloading can be prevented using _____________(a) Over-current protection(b) Speed protection(c) Over frequency protection(d) Oversize protectionThe question was asked in semester exam.Query is from Motors Rating and Heating topic in section Rating and Heating of Motors of Electric Drives
Answer» The correct CHOICE is (a) Over-current protection Best explanation: Overloading can be prevented using over-current protection. It will detect the over-current and interrupt the supply. IDMT over-current RELAY can be USED for the protection purpose.

Discussion

11.	1 Btu/h is equal to ___________(a) .641(b) .334(c) .293(d) .417This question was addressed to me by my school principal while I was bunking the class.The above asked question is from Motors Rating and Heating in division Rating and Heating of Motors of Electric Drives
Answer» Correct answer is (c) .293 Easy EXPLANATION: One British thermal UNIT is equal to .293 Watt. 1 Btu/h is the amount of energy REQUIRES to increase the temperature of one pound of WATER by 1℉.

Discussion

12.	Calculate the heat loss in the electric motor for time interval 0-5 sec using the following data: Ia=2 A, Ra=.8Ω.(a) 16 J-sec(b) 14 J-sec(c) 12 J-sec(d) 10 J-secI have been asked this question by my college professor while I was bunking the class.This question is from Motors Rating and Heating topic in chapter Rating and Heating of Motors of Electric Drives
Answer» The correct answer is (a) 16 J-sec To explain: The heat loss can be CALCULATED USING the Joule LAW of HEATING effect. The value of the heat loss is Ia^2×Ra×t=4×4=16 J-sec.

Discussion

13.	What is the range of size of the motor (kW) for efficiency nearly equals to 90%?(a) 15-150(b) 0-2(c) 3-15(d) 150-250This question was addressed to me by my college director while I was bunking the class.The query is from Motors Rating and Heating in division Rating and Heating of Motors of Electric Drives
Answer» Right choice is (a) 15-150 For EXPLANATION I WOULD say: As the size of the motor INCREASES its SPEED decreases. The range of size of the motor (kW) for efficiency nearly equals to 90 % is 15-150. The efficiency increases as the size increases.

Discussion

14.	Which test is used to determine the conditions where electric motors are being used?(a) Thermography(b) Geography(c) Seismography(d) AnthropologyI got this question during an online interview.The doubt is from Motors Rating and Heating topic in chapter Rating and Heating of Motors of Electric Drives
Answer» Right ANSWER is (a) Thermography Explanation: Thermography is used to detect HEAT patterns. It uses an Infrared RAYS CAMERA. This test is used to determine the conditions where electric motors are being used.

Discussion

15.	Which device is used to store the energy during load equalization?(a) Flywheel(b) Capacitor(c) Inductor(d) ResistorI got this question by my college director while I was bunking the class.The question is from Motors Rating and Heating in portion Rating and Heating of Motors of Electric Drives
Answer» The correct answer is (a) Flywheel The best explanation: Flywheel is used to store the energy during LOAD equalization. It acts as a reservoir. It STORES the energy during LIGHT load and utilizes the stored energy during PEAK load conditions.

Discussion

16.	What is Load Equalisation?(a) Process of smoothing the fluctuating load(b) Process of removing the load(c) Process of changing the voltage level(d) Process of changing the speedThe question was posed to me by my school principal while I was bunking the class.My question is based upon Motors Rating and Heating in chapter Rating and Heating of Motors of Electric Drives
Answer» Correct answer is (a) PROCESS of smoothing the FLUCTUATING load The best explanation: The Load Equalisation is the process of smoothing the fluctuating load. Load fluctuation causes a large voltage dip in the SYSTEM and can damage the device.

Discussion

17.	Calculate the heat absorbed by a 20 Ω resistor when 40 V is applied across it.(a) 120 W(b) 100 W(c) 80 W(d) 110 WI got this question in an internship interview.Enquiry is from Motors Rating and Heating in portion Rating and Heating of Motors of Electric Drives
Answer» Right option is (c) 80 W Best explanation: The resistor always absorbs ACTIVE power and dissipates in the form of the HEAT. Power ABSORBED by a 20 Ω resistor is 40×40÷20=80 W.

Discussion

18.	Full form of VFD is _____________(a) Variable frequency drive(b) Variable force drive(c) Value frequency drive(d) Variable force diverterThe question was posed to me during a job interview.My question is taken from Motors Rating and Heating in chapter Rating and Heating of Motors of Electric Drives
Answer» RIGHT option is (a) VARIABLE frequency drive To EXPLAIN I would say: VFD STANDS for variable frequency drive. It is a controller for AC or DC motors to achieve the desired speed. It can perform the four quadrant operation.

Discussion

19.	Choose the correct relationship in Star connection with the positive sequence.(a) VL=Vp(b) VL=√3Vp(c) VL=√2Vp(d) IL=√3IpThis question was posed to me during a job interview.My doubt is from Power Rating Determination of Electric Motors for Different Applications topic in portion Rating and Heating of Motors of Electric Drives
Answer» The correct choice is (b) VL=√3Vp The BEST EXPLANATION: In the star connection line current is the same as the phase current. The line voltage is √3 times of the phase voltage and leads by 30°.

Discussion

20.	Choose the correct relationship in delta connection with the positive sequence.(a) IL=Ip(b) VL=√3Vp(c) VL=Vp(d) IL=√3IpI had been asked this question during an interview.I'd like to ask this question from Power Rating Determination of Electric Motors for Different Applications in section Rating and Heating of Motors of Electric Drives
Answer» RIGHT CHOICE is (d) IL=√3Ip Explanation: In the delta CONNECTION line voltage is the same as the PHASE voltage. The line current is √3 times of the phase current and LEADS by 30°.

Discussion

21.	Calculate the heating time constant of the machine if the thermal capacity (c) of the machine is 16 watts/℃ and heat dissipation constant value (D) is 4 watts/℃.(a) 6 sec(b) 7 sec(c) 4 sec(d) 9 secThis question was posed to me during an interview for a job.Origin of the question is Motors Rating and Heating topic in chapter Rating and Heating of Motors of Electric Drives
Answer» Correct option is (c) 4 sec Best EXPLANATION: The HEATING time constant of the machine is the ratio of the THERMAL capacity of the machine and heat dissipation constant value. τ = c÷D = 16÷4 = 4 sec.

Discussion

22.	Calculate the compensator rating required for sin(Φ)=.8.(a) 0.9 P.U(b) 0.8 P.U(c) 0.7 P.U(d) 0.2 P.UI had been asked this question in final exam.Asked question is from Motors Rating and Heating topic in section Rating and Heating of Motors of Electric Drives
Answer» Correct choice is (b) 0.8 P.U To explain I would say: The compensator RATING can be CALCULATED using the relation QP.U=√1-cos^2(∅)=sin(∅)=.8. This per unit value VAR compensator is required to IMPROVE the power factor of the system.

Discussion

23.	The Speed control by variation of field flux results in _____________(a) Constant torque drive(b) zero speed(c) Variable torque drive(d) Variable power driveThe question was posed to me by my college professor while I was bunking the class.This intriguing question originated from Motors Rating and Heating topic in section Rating and Heating of Motors of Electric Drives
Answer» Correct option is (c) Variable TORQUE drive To elaborate: Field FLUX control method is used to achieve the speed above the BASE speed. It PROVIDES constant power drive and variable torque drive.

Discussion

24.	Which type of force phenomenon is used in Sugar mills?(a) Centripetal force(b) Centrifugal force(c) Electrostatic force(d) Nuclear forcesThe question was asked in an online quiz.This is a very interesting question from Motors Rating and Heating in portion Rating and Heating of Motors of Electric Drives
Answer» Correct answer is (b) Centrifugal FORCE For explanation I would say: In sugar mills, a centrifugal is used to separate out sugar CRYSTALS from the syrup by the action of centrifugal forces. Centrifugal force ACTS away from the CENTER.

Discussion

25.	Calculate the work done in stretching the wire of length=2 m and the values of stress and strain are 16 N/m^2 and 24.(a) 1566 J(b) 1644 J(c) 1522 J(d) 1536 JThe question was posed to me by my college director while I was bunking the class.Origin of the question is Motors Rating and Heating topic in division Rating and Heating of Motors of Electric Drives
Answer» Correct choice is (d) 1536 J Easiest EXPLANATION: The work DONE in stretching a wire is .5×Stress×Strain×Volume. The value of the work done is .5×8×16×24=1536 J. The volume of wire is 2×2×2=8 m^3.

Discussion

26.	Which type of motor is used for milling and grinding operations?(a) SCIM(b) WRIM(c) Split phase(d) Reluctance motorThe question was asked in my homework.This key question is from Motors Rating and Heating topic in portion Rating and Heating of Motors of Electric Drives
Answer» The correct CHOICE is (a) SCIM The explanation is: Squirrel CAGE Induction motor is used for milling and grinding operations. SCIM has a RIGID structure and high tolerating capability. It provides GOOD running characteristics.

Discussion

27.	Which of the following are the types of Longitudinal stress?(a) Tensile stress, Compressive stress(b) Tensile stress, Volume stress(c) Tensile stress, Shear stress(d) Tensile stress, Lateral stressThis question was addressed to me in an international level competition.My doubt is from Motors Rating and Heating in chapter Rating and Heating of Motors of Electric Drives
Answer» The correct choice is (a) TENSILE stress, COMPRESSIVE stress Best EXPLANATION: Longitudinal stress is one the type of stress. Longitudinal stress is of TWO TYPES. It consists of Tensile stress and Compressive stress. It has a unit of N/m^2.

Discussion

28.	Capacitor start capacitor run single-phase Induction motor is used in ceiling fan.(a) True(b) FalseThe question was posed to me in an online quiz.My question is based upon Motors Rating and Heating in section Rating and Heating of Motors of Electric Drives
Answer» RIGHT answer is (a) True The explanation: CAPACITOR start capacitor RUN single-phase Induction motor is used in ceiling FAN. The motor operation is silent and non-vibrational. It provides a high starting torque.

Discussion

29.	Electric motor and control system are the basic elements of the electric drive.(a) True(b) FalseThis question was addressed to me in a national level competition.My question is based upon Motors Rating and Heating topic in portion Rating and Heating of Motors of Electric Drives
Answer» Correct option is (a) True Easiest explanation: ELECTRIC motor and control system are the BASIC elements of the electric drive. The electric drive USES the control system methods to control the speed and TORQUE of the motor.

Discussion

30.	Calculate the moment of inertia of the flywheel of mass 45 kg and radius of 2 m.(a) 185 kg-m^2(b) 180 kg-m^2(c) 175 kg-m^2(d) 170 kg-m^2This question was posed to me in an interview.My question comes from Motors Rating and Heating in chapter Rating and Heating of Motors of Electric Drives
Answer» Correct CHOICE is (B) 180 kg-m^2 Easiest explanation: The moment of INERTIA of the flywheel can be calculated using the FORMULA I=M(R^2). The mass of flywheel and radius is given. I=(45)×(2)^2=180 kg-m^2. It depends upon the orientation of the rotational axis.

Discussion

31.	Calculate the mass of the solid cylinder having a mass of 4 kgm^2 and radius of 4 m & length of 12 m.(a) 64 kgm^2(b) 68 kgm^2(c) 67 kgm^2(d) 69 kgm^2I got this question in homework.My question is from Motors Rating and Heating in section Rating and Heating of Motors of Electric Drives
Answer» RIGHT choice is (a) 64 kgm^2 The explanation is: The moment of inertia of the solid cylinder can be calculated using the FORMULA I= M(l^2÷12+R2^2÷4). The mass of solid cylinder and radius, the length is GIVEN. I=(4){(16)}= 64 kgm^2. It depends upon the orientation of the rotational axis.

Discussion

32.	Calculate the moment of inertia of the circular hollow disk having a mass of 2 kg and an internal radius of 5 m and an external radius of 10 m.(a) 125 kgm^2(b) 127 kgm^2(c) 122 kgm^2(d) 123 kgm^2This question was posed to me by my school principal while I was bunking the class.My query is from Motors Rating and Heating topic in division Rating and Heating of Motors of Electric Drives
Answer» Right answer is (a) 125 kgm^2 For explanation: The moment of inertia of the circular HOLLOW disk can be calculated USING the FORMULA I=M(R1^2+R2^2)÷2. The mass of circular hollow disk and radius is given. I=(1)×{(5)^2+(10)^2}=125 kgm^2. It depends upon the orientation of the ROTATIONAL axis.

Discussion

33.	Lowest order harmonic present in 3-Φ fully controlled rectifier is __________(a) 5^th(b) 7^th(c) 3^rd(d) 2^ndThe question was posed to me during an interview.The above asked question is from Motors Rating and Heating in section Rating and Heating of Motors of Electric Drives
Answer» The correct choice is (a) 5^th The explanation: Only 6k±1 order harmonics are PRESENT in 3-Φ fully controlled rectifier. The LOWEST order harmonic is 5^th harmonic for k=1. THIRD order harmonics are ABSENT in 3-Φ fully controlled rectifier.

Discussion

34.	Which harmonic is not present in 3-Φ fully controlled rectifier?(a) 3^rd harmonic(b) 5^th harmonic(c) 7^th harmonic(d) 11^th harmonicThis question was addressed to me at a job interview.My enquiry is from Motors Rating and Heating in division Rating and Heating of Motors of Electric Drives
Answer» The correct CHOICE is (a) 3^rd harmonic Easiest explanation: Triplen harmonics are ABSENT in the case of 3-phase fully controlled RECTIFIER. Because of the absence of triplen harmonics THD of the rectifier 31%.

Discussion

35.	Full form of SPWM.(a) Sinusoidal pulse width modulation(b) State per width modulation(c) State pulse width modulation(d) Sinusoidal per width modulationI had been asked this question during an interview for a job.My question is taken from Motors Rating and Heating in division Rating and Heating of Motors of Electric Drives
Answer» RIGHT OPTION is (a) Sinusoidal pulse width modulation The best explanation: SPWM stands for sinusoidal pulse width modulation. SPWM is a high-frequency PWM technique. This technique is USED to achieve variable VOLTAGE level.

Discussion

36.	_________ motor operates at low power factor.(a) Capacitor run(b) Capacitor start(c) Shaded pole(d) ReluctanceThe question was asked during an interview for a job.My enquiry is from Motors Rating and Heating in chapter Rating and Heating of Motors of Electric Drives
Answer» Right option is (c) Shaded pole The best I can explain: Shaded pole MOTORS operate at a low power factor. There is a weak MAGNETIC FIELD DEVELOPS in the case of Shaded pole motor. It is a single-phase AC Induction motor.

Discussion

37.	Calculate the compensator rating required for cos(Φ)=.7.(a) 0.71 P.U(b) 0.21 P.U(c) 0.47 P.U(d) 0.12 P.UThis question was addressed to me in an interview for internship.My question is based upon Motors Rating and Heating in portion Rating and Heating of Motors of Electric Drives
Answer» The correct option is (a) 0.71 P.U Easy EXPLANATION: The compensator rating can be calculated USING the RELATION QP.U=√1-cos^2(∅)=√1-.49=.71. This per unit value VAR compensator is required to IMPROVE the power factor of the system.

Discussion

38.	Plasticity is the ability of the material to deform without breaking.(a) True(b) FalseI had been asked this question in unit test.The question is from Motors Rating and Heating in chapter Rating and Heating of Motors of Electric Drives
Answer» Correct option is (a) True For explanation I WOULD say: Plasticity is the ability of the material to DEFORM WITHOUT breaking. Plastic DEFORMATION occurs in metal forming PROCESSES.

Discussion

39.	Calculate the work done in stretching the wire of volume=22 m^3 and the values of stress and strain are 2 N/m^2 and 4.(a) 66 J(b) 44 J(c) 22 J(d) 88 JThe question was posed to me in my homework.This interesting question is from Motors Rating and Heating in section Rating and Heating of Motors of Electric Drives
Answer» The correct answer is (d) 88 J Explanation: The WORK done in STRETCHING a WIRE is .5×Stress×Strain×Volume. The value of the work done is .5×22×4×2=88 J.

Discussion

40.	The relationship between Young’s modulus (Y), Bulk modulus (K) and Poisson’s ratio (μ) is _____________(a) Y=K(1-2μ)(b) Y=3K(1-2μ)(c) Y=5K(1-2μ)(d) Y=4K(1-8μ)This question was addressed to me in examination.My enquiry is from Motors Rating and Heating topic in division Rating and Heating of Motors of Electric Drives
Answer» Right choice is (b) Y=3K(1-2μ) To elaborate: The relationship between Young’s modulus (Y), Bulk modulus (K) and POISSON’s ratio (μ) is Y=3K(1-2μ). The Young modulus of ELASTICITY is defined as the ratio of Longitudinal stress and Longitudinal STRAIN.

Discussion

41.	Which of the following are the types of Stress?(a) Longitudinal stress, Volume stress, Tangential stress(b) Longitudinal stress, Volume stress(c) Longitudinal stress, Lateral stress, Tangential stress(d) Longitudinal stress, Shear stressI had been asked this question in a national level competition.My doubt is from Motors Rating and Heating in section Rating and Heating of Motors of Electric Drives
Answer» The correct option is (a) Longitudinal stress, Volume stress, Tangential stress To ELABORATE: There are THREE TYPES of stress that are Longitudinal stress, Volume stress, Tangential or SHEAR stress. Stress is the RATIO of restoring force and cross-section area.

Discussion

42.	What is the effect of impurities on elasticity?(a) It will increase(b) Remains the same(c) It will decrease(d) It will slightly increaseI have been asked this question during an internship interview.This interesting question is from Motors Rating and Heating in division Rating and Heating of Motors of Electric Drives
Answer» The correct answer is (d) It will slightly increase Easy explanation: The Young MODULUS of ELASTICITY is slightly increased by the addition of impurities. The intermolecular forces inside the wire EFFECTIVELY increase by impurity due to this external FORCE can be easily opposed.

Discussion

43.	Calculate the load stress if the value of force is 20 N and the area of cross-section is 2 m^2.(a) 10 N/m^2(b) 20 N/m^2(c) 30 N/m^2(d) 40 N/m^2I have been asked this question during an interview for a job.Question is from Motors Rating and Heating topic in division Rating and Heating of Motors of Electric Drives
Answer» The correct CHOICE is (a) 10 N/m^2 The best I can EXPLAIN: The STRESS is defined as the ratio of the internal RESTORING FORCE and area of the cross-section. Stress=Fres÷A=20÷2=10 N/m^2.

Discussion

44.	Hooke’s law is applicable within the elastic limit.(a) True(b) FalseI had been asked this question in final exam.Enquiry is from Motors Rating and Heating topic in portion Rating and Heating of Motors of Electric Drives
Answer» Correct choice is (a) True For explanation I would SAY: Hooke’s law is only APPLICABLE WITHIN the elastic limit. It states that within the elastic limit the strain is directly proportional to the STRESS.

Discussion

45.	Calculate the 3-∅ power developed in the IM connected in star using the following data: Vp=7 V, IL=7 A, cosΦ=.6.(a) 88.5 W(b) 88.4 W(c) 88.8 W(d) 88.2 WThe question was asked in quiz.My enquiry is from Power Rating Determination of Electric Motors for Different Applications in division Rating and Heating of Motors of Electric Drives
Answer» CORRECT choice is (d) 88.2 W Easy explanation: The power developed in the IM is √3VLILcos∅. The power is INDEPENDENT of time and frequency. In STAR connection VL=√3Vp=12.12 V. P=√3VLILcos∅=3×20×5×.8=88.2 W.

Discussion

46.	What is the relationship between line and phase current in Star connection with the positive sequence?(a) VL=Vp(b) VL=√9Vp(c) VL=√2Vp(d) IL=IpI got this question in examination.My question is taken from Power Rating Determination of Electric Motors for Different Applications in division Rating and Heating of Motors of Electric Drives
Answer» The correct option is (d) IL=Ip The BEST I can explain: In the STAR connection LINE current is the same as the phase current. The line VOLTAGE is √3 times of the phase voltage and leads by 30°.

Discussion

47.	What is the correct relationship between the phase voltage and line voltage in Delta connection with the positive sequence?(a) VL=Vp(b) VL=√3Vp(c) VL=√2Vp(d) IL=√2IpThe question was posed to me in unit test.My question comes from Power Rating Determination of Electric Motors for Different Applications topic in section Rating and Heating of Motors of Electric Drives
Answer» The CORRECT option is (a) VL=Vp Explanation: In the delta connection line VOLTAGE is the same as the phase voltage. The line current is √3 TIMES of the phase current and leads by 30°.

Discussion

48.	Full form of PWM.(a) Pulse width modulation(b) Pulse run modulation(c) Power width modulation(d) Pulse wisdom modeThis question was posed to me by my college director while I was bunking the class.This is a very interesting question from Power Rating Determination of Electric Motors for Different Applications topic in section Rating and Heating of Motors of Electric Drives
Answer» The correct OPTION is (a) Pulse width modulation The BEST I can EXPLAIN: PWM stands for pulse width modulation. This TECHNIQUE is used to alter the VOLTAGE level of the output of the inverter. We can control the voltage level using the PWM technique.

Discussion

49.	Calculate the average power dissipated if the value of the duty cycle is .5 and Pmax=12 W.(a) 6 W(b) 5 W(c) 4 W(d) 3 WThe question was posed to me during an online exam.My doubt stems from Power Rating Determination of Electric Motors for Different Applications in chapter Rating and Heating of Motors of Electric Drives
Answer» CORRECT OPTION is (a) 6 W To ELABORATE: The average power dissipated can be calculated using the relation Pavg=D×Pmax. The value of the average power is .5×12=6 W.

Discussion

50.	Calculate mark to space ratio if the system is on for 20 sec and off for 3 sec.(a) 6.66(b) 4.48(c) 8.2(d) 5.6This question was addressed to me during a job interview.Asked question is from Power Rating Determination of Electric Motors for Different Applications topic in division Rating and Heating of Motors of Electric Drives
Answer» The CORRECT CHOICE is (a) 6.66 Explanation: Mark to space RATIO is Ton÷Toff. It is the ratio of time for which the system is active and the time for which is INACTIVE. M = Ton÷Toff=20÷3=6.66.

Discussion

Explore topic-wise InterviewSolutions in .

Second lowest order harmonic present in 3-Φ fully controlled rectifier is __________(a) 5^th(b) 7^th(c) 3^rd(d) 2^ndI got this question during an interview.This question is from Motors Rating and Heating topic in chapter Rating and Heating of Motors of Electric Drives

Full form of VRF.(a) Voltage ripple factor(b) Voltage revert factor(c) Volume ripple factor(d) Volume revert factorI had been asked this question during an online interview.I would like to ask this question from Motors Rating and Heating in section Rating and Heating of Motors of Electric Drives

Calculate the value of THD if the distortion factor is .8.(a) 76 %(b) 75 %(c) 74 %(d) 73 %I got this question in an interview for job.My doubt stems from Motors Rating and Heating in division Rating and Heating of Motors of Electric Drives

Calculate the value of Voltage ripple factor if the Form factor is 1.1.(a) 45.8 %(b) 46.2 %(c) 47.5 %(d) 49.9 %The question was posed to me in my homework.I need to ask this question from Motors Rating and Heating in portion Rating and Heating of Motors of Electric Drives

Calculate the compensator rating required for a sec(Φ)=1.(a) 0.64 P.U(b) 0.21 P.U(c) 0.57 P.U(d) 0 P.UI have been asked this question in an interview for internship.This question is from Motors Rating and Heating topic in section Rating and Heating of Motors of Electric Drives

Full form of THD is ____________(a) Total harmonic diverter(b) Total harmonic digital(c) Total harmonic distortion(d) Total harmonic discreteI had been asked this question in an internship interview.Enquiry is from Motors Rating and Heating in portion Rating and Heating of Motors of Electric Drives

The most common cause of motor failure is ____________(a) Overloading(b) Low resistance(c) Contamination(d) Over-HeatingI had been asked this question in semester exam.The above asked question is from Motors Rating and Heating topic in division Rating and Heating of Motors of Electric Drives

Overloading can be prevented using _____________(a) Over-current protection(b) Speed protection(c) Over frequency protection(d) Oversize protectionThe question was asked in semester exam.Query is from Motors Rating and Heating topic in section Rating and Heating of Motors of Electric Drives

1 Btu/h is equal to ___________(a) .641(b) .334(c) .293(d) .417This question was addressed to me by my school principal while I was bunking the class.The above asked question is from Motors Rating and Heating in division Rating and Heating of Motors of Electric Drives

Which device is used to store the energy during load equalization?(a) Flywheel(b) Capacitor(c) Inductor(d) ResistorI got this question by my college director while I was bunking the class.The question is from Motors Rating and Heating in portion Rating and Heating of Motors of Electric Drives

Calculate the heat absorbed by a 20 Ω resistor when 40 V is applied across it.(a) 120 W(b) 100 W(c) 80 W(d) 110 WI got this question in an internship interview.Enquiry is from Motors Rating and Heating in portion Rating and Heating of Motors of Electric Drives

Full form of VFD is _____________(a) Variable frequency drive(b) Variable force drive(c) Value frequency drive(d) Variable force diverterThe question was posed to me during a job interview.My question is taken from Motors Rating and Heating in chapter Rating and Heating of Motors of Electric Drives

Calculate the compensator rating required for sin(Φ)=.8.(a) 0.9 P.U(b) 0.8 P.U(c) 0.7 P.U(d) 0.2 P.UI had been asked this question in final exam.Asked question is from Motors Rating and Heating topic in section Rating and Heating of Motors of Electric Drives

Which type of motor is used for milling and grinding operations?(a) SCIM(b) WRIM(c) Split phase(d) Reluctance motorThe question was asked in my homework.This key question is from Motors Rating and Heating topic in portion Rating and Heating of Motors of Electric Drives

Capacitor start capacitor run single-phase Induction motor is used in ceiling fan.(a) True(b) FalseThe question was posed to me in an online quiz.My question is based upon Motors Rating and Heating in section Rating and Heating of Motors of Electric Drives

Electric motor and control system are the basic elements of the electric drive.(a) True(b) FalseThis question was addressed to me in a national level competition.My question is based upon Motors Rating and Heating topic in portion Rating and Heating of Motors of Electric Drives

Calculate the moment of inertia of the flywheel of mass 45 kg and radius of 2 m.(a) 185 kg-m^2(b) 180 kg-m^2(c) 175 kg-m^2(d) 170 kg-m^2This question was posed to me in an interview.My question comes from Motors Rating and Heating in chapter Rating and Heating of Motors of Electric Drives

Calculate the mass of the solid cylinder having a mass of 4 kgm^2 and radius of 4 m & length of 12 m.(a) 64 kgm^2(b) 68 kgm^2(c) 67 kgm^2(d) 69 kgm^2I got this question in homework.My question is from Motors Rating and Heating in section Rating and Heating of Motors of Electric Drives

Lowest order harmonic present in 3-Φ fully controlled rectifier is __________(a) 5^th(b) 7^th(c) 3^rd(d) 2^ndThe question was posed to me during an interview.The above asked question is from Motors Rating and Heating in section Rating and Heating of Motors of Electric Drives

Which harmonic is not present in 3-Φ fully controlled rectifier?(a) 3^rd harmonic(b) 5^th harmonic(c) 7^th harmonic(d) 11^th harmonicThis question was addressed to me at a job interview.My enquiry is from Motors Rating and Heating in division Rating and Heating of Motors of Electric Drives

_________ motor operates at low power factor.(a) Capacitor run(b) Capacitor start(c) Shaded pole(d) ReluctanceThe question was asked during an interview for a job.My enquiry is from Motors Rating and Heating in chapter Rating and Heating of Motors of Electric Drives

Calculate the compensator rating required for cos(Φ)=.7.(a) 0.71 P.U(b) 0.21 P.U(c) 0.47 P.U(d) 0.12 P.UThis question was addressed to me in an interview for internship.My question is based upon Motors Rating and Heating in portion Rating and Heating of Motors of Electric Drives

Plasticity is the ability of the material to deform without breaking.(a) True(b) FalseI had been asked this question in unit test.The question is from Motors Rating and Heating in chapter Rating and Heating of Motors of Electric Drives

Hooke’s law is applicable within the elastic limit.(a) True(b) FalseI had been asked this question in final exam.Enquiry is from Motors Rating and Heating topic in portion Rating and Heating of Motors of Electric Drives