124 + Interview Questions in Transformers in Electrical Machines Page 1 InterviewSolution

1.	If the per unit leakage impedance for the primary of a transformer is ‘x’ on the given rated base value. If the voltage and volt-amperes are halved, then the changed per unit impedance will be ___________(a) 0.5x(b) 2x(c) 4x(d) xThis question was addressed to me during a job interview.The query is from Voltage Regulation of Transformer topic in chapter Transformers of Electrical Machines
Answer» Correct CHOICE is (b) 2x The EXPLANATION is: pu(NEW base) = (X)(MVA(new)/MVA(old))(kV(old)/kV(new))^2 = x0.5(4/) = 2x.

Discussion

2.	The voltage regulation fortransformer is given by ___________(a) (E2-V2)/E2(b) (E2-V2)/V2(c) (V2-E2)/E2(d) (V2-E2)/V2The question was posed to me in semester exam.I need to ask this question from Voltage Regulation of Transformer in section Transformers of Electrical Machines
Answer» Correct answer is (a) (E2-V2)/E2 For EXPLANATION I would SAY: Voltage REGULATION is the change in SECONDARY voltage with secondary rated voltage.

Discussion

3.	Two tranformer having same voltage but different KVA are operating in parallel. For a good load sharing __________(a) impedance must be equal(b) pu impedances must be equal(c) pu impedance and X/R ratios must be equal(d) impedance and X/R ratios must be equalThis question was posed to me during an internship interview.I need to ask this question from Autotransformers topic in division Transformers of Electrical Machines
Answer» Correct answer is (c) pu impedance and X/R ratios must be equal The best I can explain: Both the conditions are to be MET in ORDER to have an EFFICIENT operation while in PARALLEL condition.

Discussion

4.	When a transformer winding suffers a short circuit, then inter turns of the same winding experience ______ forces.(a) an attractive(b) a repulsive(c) no force(d) may be attractive or repulsive typeThe question was posed to me in an internship interview.This interesting question is from Autotransformers in portion Transformers of Electrical Machines
Answer» Right answer is (a) an attractive Explanation: As the current will FLOW in one direction, attractive force will appear across the inter TURNS as PER Biot-savart’s LAW.

Discussion

5.	In a transformer, we place the tapping windings at the middle because __________(a) of radial forces on the windings(b) axial forces on the windings(c) insulation level of the winding(d) to provide a mechanical balance to the windingsI got this question during an interview for a job.I'm obligated to ask this question of Autotransformers in portion Transformers of Electrical Machines
Answer» The correct choice is (b) axial FORCES on the windings For EXPLANATION I would say: DUE to TWO different voltages, different currents will flow in the windings and it will cause the axial forces due to currents interaction appear causing DAMAGE.

Discussion

6.	The tappings on the transformers is provided on __________(a) h.v side at one end of the winding(b) l.v. side at one end of the winding(c) h.v side at middle(d) l.v side at middleI had been asked this question in my homework.My question is based upon Autotransformers topic in section Transformers of Electrical Machines
Answer» CORRECT option is (c) h.v side at middle The explanation: High VOLTAGE side winding has more voltage so the variation of the voltage will be more and BETTER APPLICABLE. And it is better to place at the middle because it gives UNIFORM voltage distribution by eliminating axial forces.

Discussion

7.	If a transformer is at no load, then it will act like __________(a) a resistor at p.f = 0(b) an inductive reactor at 0.2 lagging(c) a capacitive reactor at0.2 leading(d) an inductive reactor at 0.8 laggingThe question was asked in examination.The above asked question is from Autotransformers in section Transformers of Electrical Machines
Answer» The CORRECT answer is (b) an inductive reactor at 0.2 lagging To explain I would SAY: Transformer is nothing but the arranged windings which are MAGNETICALLY coupled. The windings will inductive predominantly with very low RESISTANCE.

Discussion

8.	A 1-phase tranformer has a leakage impedance of 1+ j4 Ω for primary and 3+ j11 Ω for secondary windings. This transformer has __________(a) H.V primary(b) Medium voltage primary(c) L.V primary(d) L.V secondaryI got this question in an international level competition.This is a very interesting question from Autotransformers topic in chapter Transformers of Electrical Machines
Answer» The CORRECT answer is (C) L.V primary Easy explanation: The side which has lower impedance will have lower number of TURNS and so the low voltage side.

Discussion

9.	Maximum efficiency of a transformer for a constant load current, occurs at __________(a) at any p.f(b) zero p.f leading(c) zero p.f lagging(d) unity p.fThis question was addressed to me during an interview for a job.My question comes from Autotransformers topic in chapter Transformers of Electrical Machines
Answer» CORRECT option is (d) unity p.f To explain: EFFICIENCY = KVAp.f/(KVAp.f + Losses); So the efficiency is maximum at unity POWER FACTOR.

Discussion

10.	Three transformers having identical dimensions but with core of iron, aluminium and wood are wound with same number of turns and have same supply. Then choose the order for eddy current losses.(a) wood > aluminium > iron(b) aluminium > iron > wood(c) iron > wood > aluminium(d) iron > aluminium > woodThe question was asked in a national level competition.My question is taken from Autotransformers topic in portion Transformers of Electrical Machines
Answer» Correct CHOICE is (a) wood > aluminium > iron Easy EXPLANATION: The eddy current losses are dependent on resistance offered to the currents. Wood is an INSULATOR so it will get HEATED up most.

Discussion

11.	Three transformers having identical dimensions but with core of iron, aluminium and wood are wound with same number of turns and have same supply. Then choose the order for hysteresis losses.(a) wood > aluminium > iron(b) aluminium > iron > wood(c) iron > wood > aluminium(d) iron > aluminium > woodThis question was addressed to me in exam.I need to ask this question from Autotransformers in chapter Transformers of Electrical Machines
Answer» The correct ANSWER is (d) iron > ALUMINIUM > wood The best I can explain: HYSTERESIS LOSSES occur maximum in the ferromagnetic material.

Discussion

12.	The voltage regulation of a transformer at full-load 0.8 p.f leading is -2%. Its voltage regulation at full load 0.8 p.f lagging _____________(a) will be positive(b) will be negative(c) may be positive(d) may be negativeThe question was posed to me in a job interview.This is a very interesting question from Autotransformers in section Transformers of Electrical Machines
Answer» CORRECT answer is (a) will be POSITIVE The BEST explanation: The leading p.f. has NEGATIVE v.r. and lagging p.f. has MAJOR portion of positive voltage regulation.

Discussion

13.	While comparing potential transformer to an auto transformer, a potential transformer transfers power ________(a) conductively(b) inductively(c) both conductively as well as inductively(d) electromagnetic inductionI got this question by my school principal while I was bunking the class.Question is from Autotransformers in section Transformers of Electrical Machines
Answer» The CORRECT OPTION is (a) conductively Explanation: Potential divider is resistance division and it does not TAKE part in INDUCTION processes.

Discussion

14.	Shape of emf generated by delta connected transformer is not always sinusoidal.(a) True(b) FalseI got this question in semester exam.This intriguing question originated from Three Phase Transformers in chapter Transformers of Electrical Machines
Answer» Correct choice is (b) False The explanation: No, for a delta TRANSFORMER, CLOSED PATH is present to generate 3rd harmonics current and so the EMF will be sinusoidal always.

Discussion

15.	A recording of the output of the emf induced for star and delta are recorded. Then shape of the emf induced in Y-connected 3-phase transformer is non sinusoidal in nature due to ___________(a) 3rd harmonic component of currents is absent(b) 3rd harmonic component of currents is present(c) negative sequence component of current is present(d) none of the mentionedThis question was addressed to me in homework.Question is taken from Three Phase Transformers topic in portion Transformers of Electrical Machines
Answer» The correct option is (a) 3rd harmonic COMPONENT of currents is absent To explain: In a star connected TRANSFORMER, closed PATH to generate 3rd harmonic is not there. So the emf SHAPE will be peaky in NATURE.

Discussion

16.	While using three phase transformers, it is taken care about the third harmonics current in the system. This is present when transformer set is delta on either side.(a) True(b) FalseI have been asked this question in unit test.My question is taken from Three Phase Transformers in portion Transformers of Electrical Machines
Answer» Correct choice is (a) True To ELABORATE: Third harmonic current are co-phase in nature and require CLOSED path which is PRESENT in delta CONNECTED only.

Discussion

17.	A 400 V, 10 KVA transformer at 50 Hz, is operated at the frequency of 40 Hz, then the humming ___________(a) increases(b) decreases(c) remains same(d) increases to very highThis question was addressed to me in an online quiz.I'd like to ask this question from Three Phase Transformers topic in division Transformers of Electrical Machines
Answer» Right option is (a) INCREASES The explanation: If the FREQUENCY is reduced, the core flux DENSITY increases, so the noise ALSO will increase.

Discussion

18.	When we magnetize the ferromagnetic core of the transformer, core length_______ and it ______ when demagnetized.(a) decreases, increases(b) decreases, decreases(c) increases,increases(d) none of the mentionedThis question was addressed to me in examination.My enquiry is from Three Phase Transformers topic in chapter Transformers of Electrical Machines
Answer» Correct OPTION is (a) decreases, increases To explain I would say: Due to aligned magnetic dipoles in the material, the size will reduce by a small MARGIN and vice VERSA while demagnetization.

Discussion

19.	If para magnetic core is used in the place of the ferromagnetic core of the transformer, then magnetostriction will ___________(a) be vanished(b) reduce(c) increase(d) not be affectedThe question was asked in my homework.Question is taken from Three Phase Transformers in portion Transformers of Electrical Machines
Answer» Right CHOICE is (a) be vanished To EXPLAIN I would SAY: If the core is not FERROMAGNETIC then the transformer will not operate at all so no HUMMING sound.

Discussion

20.	Below is the circuit diagram for delta-delta transformer have a transformation ratio ‘k’. The current flowing in the windings of phase r-y in the below diagrams is?(a) kI/1.73(b) I/k1.73(c) 1.73kI(d) 3kII got this question during an internship interview.This intriguing question comes from Three Phase Transformers topic in portion Transformers of Electrical Machines
Answer» The CORRECT ANSWER is (a) k*I/1.73 To ELABORATE: The phase current will be REDUCED by 1/1.73.

Discussion

21.	If one of the transformers is removed from the bank of only delta-delta, then it behaves with 58% power delivery.(a) True(b) FalseThe question was posed to me at a job interview.My doubt stems from Three Phase Transformers topic in portion Transformers of Electrical Machines
Answer» The CORRECT choice is (a) True For explanation: It is true as the circuit will STILL be closed and the TRANSFORMER will operate will LESSER OPERATING point.

Discussion

22.	Open delta transformers can be obtained from ___________(a) delta-delta(b) star-delta(c) delta-star(d) any of the mentionedThe question was posed to me by my college director while I was bunking the class.My doubt stems from Three Phase Transformers in portion Transformers of Electrical Machines
Answer» CORRECT CHOICE is (a) delta-delta The best explanation: If one of the transformers is REMOVED from the BANK of only delta-delta, then it behaves with 58% power delivery.

Discussion

23.	The delta-delta connections are used in applications of ___________(a) large l.v. transformers(b) small h.v. transformers(c) large h.v. transformers(d) small l.v. transformersI got this question in semester exam.Query is from Three Phase Transformers in section Transformers of Electrical Machines
Answer» CORRECT answer is (a) LARGE l.v. transformers For explanation I would say: DELTA connected winding handle LINE voltages so it needs more TURNS in the winding but thin wires.

Discussion

24.	The voltage across the terminal ‘r’ and ‘y’ is?(a) 1.73V(b) V/1.73(c) V(d) 3VI got this question during an interview for a job.This intriguing question comes from Three Phase Transformers topic in chapter Transformers of Electrical Machines
Answer» The CORRECT option is (B) V/1.73 Explanation: From STAR to delta, the line VOLTAGE will reduce by 1.73.

Discussion

25.	For the given circuit below, the voltage across the terminal ‘a’ and ‘b’ is?(a) 1.73V(b) V/1.73(c) V(d) 3VI had been asked this question by my college professor while I was bunking the class.My question is based upon Three Phase Transformers in section Transformers of Electrical Machines
Answer» Correct CHOICE is (a) 1.73*V The EXPLANATION is: From deltato star,the VOLTAGE between the lines will increase by 1.73.

Discussion

26.	The transformer which is more feasible to use in the distribution ends should be ___________(a) star-delta(b) delta-star(c) scott(d) delta-deltaI got this question during an online exam.The question is from Three Phase Transformers topic in division Transformers of Electrical Machines
Answer» Right OPTION is (a) star-delta The best EXPLANATION: Star-delta will have lower voltage at delta end.

Discussion

27.	Three units of single phase transformers and one single three-phase transformer rating ___________(a) will be same for one rating(b) can never be made same(c) may be same(d) none of the mentionedThe question was posed to me in my homework.My query is from Three Phase Transformers in chapter Transformers of Electrical Machines
Answer» Correct choice is (a) will be same for one rating The EXPLANATION: THREE single phase transformers and one single unit of three phase transformer will be same only. this is DONE to reduce the cost and spacing.

Discussion

28.	A V-V connected transformer can be connected in parallel to delta-delta connected transformer but not to ___________(a) delta-star(b) star-delta(c) star-V(d) all of the mentionedThe question was posed to me in unit test.Question is taken from Three Phase Transformers in division Transformers of Electrical Machines
Answer» Correct option is (a) delta-star For explanation: The V-V connected transformer and D-D connected transformers have same PHASE DISPLACEMENT, so they only can be connected in PARALLEL to each other.

Discussion

29.	A 10 KVA, 2000/200 V, single phase transformer operating at 50 Hz with a current of 50 A flowing through the l.v. winding. Then the Self inductance of l.v. winding is?(a) 12.7mH(b) 1.27 mH(c) 12.7H(d) 0.127 HI got this question in unit test.This intriguing question comes from Transformer as a Magnetically Coupled Circuit topic in division Transformers of Electrical Machines
Answer» CORRECT OPTION is (a) 12.7mH Easiest explanation: Flux linkages on l.v. = Nφ = E/(4.44F) = 200/(4.4450)= 0.9 AT Self inductance = MUTUAL flux linkage/peak current = 0.9/(1.41450) = 0.0127 H.

Discussion

30.	There is a 10 KVA, 2000/200 V, single phase transformer operating at 50 Hz. Maximum flux linkages in secondary will be?(a) 0.9 AT(b) 9 AT(c) 1 AT(d) 0.09 ATI have been asked this question in semester exam.The doubt is from Transformer as a Magnetically Coupled Circuit in division Transformers of Electrical Machines
Answer» The correct CHOICE is (a) 0.9 AT The explanation: Flux linkages on secondary = Nφ = E/(4.44F) = 200/(4.44*50)= 0.9 AT

Discussion

31.	There is a 10 KVA, 2000/200 V, single phase transformer having below following parameters are r1=10Ω, r2=0.1Ω, l1 = 40mH, l2=0.4 mH, M = 10H. Then the expected secondary self inductance will be?(a) 100.04H(b) 99.06H(c) 1.0004H(d) 10.04HI got this question in an interview for internship.My question is taken from Transformer as a Magnetically Coupled Circuit topic in section Transformers of Electrical Machines
Answer» CORRECT answer is (C) 1.0004H The best I can explain: Secondary SELF inductance = L2 = Lm2 + l2 = (N2/N1)M + l2 = 200/200010 + 0.0004H = 0.0004 H.

Discussion

32.	Consider a 10 KVA, 2000/200 V, single phase transformer having below following parameters are r1=10Ω, r2=0.1Ω, l1 = 40mH, l2=0.4 mH, M = 10H. Then the expected primary self inductance will be?(a) 100.04H(b) 99.06H(c) 1.0004H(d) 10.04HThis question was addressed to me in class test.This interesting question is from Transformer as a Magnetically Coupled Circuit topic in chapter Transformers of Electrical Machines
Answer» Correct CHOICE is (a) 100.04H Easiest EXPLANATION: PRIMARY SELF inductance = L1 = Lm1 + l1 = (N1/N2)M + l1 = 2000/20010 + 0.04 =100.04 H.

Discussion

33.	The voltage regulation of a transformer at full-load 0.8 p.f lagging is 2%. Its voltage regulation at full load 0.8 p.f leading _____________(a) will be positive(b) will be negative(c) may be positive(d) may be negativeI had been asked this question in exam.My doubt stems from Transformer as a Magnetically Coupled Circuit topic in section Transformers of Electrical Machines
Answer» The CORRECT OPTION is (B) will be NEGATIVE Explanation: The LEADING p.f. has negative v.r.

Discussion

34.	In a transformer,eddy-current loss is 1000 watts which is half of the total core loss. If thickness of lamination and frequency are increased by 10%, What is the new core-losses?(a) 3200W(b) 3300W(c) 2200W(d) 3100WThe question was asked in an interview.Origin of the question is Transformer as a Magnetically Coupled Circuit in division Transformers of Electrical Machines
Answer» The CORRECT CHOICE is (a) 3200W The explanation: Pe = 1000W, Pi = 2000W Here, V/f = constant Pe will be same 1000W, Pi = 200+2000 = 2200W Total CORE losses = 1000+2200 = 3200W.

Discussion

35.	The voltage conversion ratio of the transformer is inverse of the current transformation.(a) True(b) FalseThe question was posed to me in quiz.This intriguing question originated from Transformer as a Magnetically Coupled Circuit topic in chapter Transformers of Electrical Machines
Answer» CORRECT OPTION is (a) TRUE Easiest EXPLANATION: It is true because, V1/V2 = N2/N1;I2/I1=1/N.

Discussion

36.	Transients currents are maximum in the transformer when it is switched on with secondary ______and when input voltage wave is passing through ________(a) open, zero(b) open, peak(c) closed, zero(d) closed, peakThis question was addressed to me in semester exam.My doubt is from Transformer as a Magnetically Coupled Circuit topic in portion Transformers of Electrical Machines
Answer» The correct option is (a) OPEN, zero The explanation is: At t=0, the current flowing will be very HIGH as EMF is very high due to t = 0.

Discussion

37.	Primary and the secondary winding of the transformer are interlaced mainly for __________(a) reducing leakage flux(b) reducing cost(c) reducing heating(d) saving the copper of the windingI had been asked this question during an online exam.This interesting question is from Transformer as a Magnetically Coupled Circuit topic in chapter Transformers of Electrical Machines
Answer» Right ANSWER is (a) REDUCING LEAKAGE flux The explanation: INTERLACING is done to provide less air gaps and improvedefficiency by reduction of leakage fluxes around the core.

Discussion

38.	It is advised to coat the laminations of the core with some enamel, to ensure __________(a) insulation(b) adhesion of laminations(c) reduction in hummingsound(d) all of the mentionedThis question was addressed to me during an online interview.My question is from Transformer as a Magnetically Coupled Circuit topic in section Transformers of Electrical Machines
Answer» Correct CHOICE is (a) INSULATION Best EXPLANATION: It is done to PROVIDE insulation.

Discussion

39.	In power transformers, it is found that the iron or core losses practically varies very less, this is because ____________(a) constant core flux(b) constant leakage flux(c) constant leakage and core flux(d) constant load currentThe question was asked at a job interview.The origin of the question is Transformer as a Magnetically Coupled Circuit topic in portion Transformers of Electrical Machines
Answer» Correct option is (a) constant CORE flux Easy explanation: DUE to the constant core flux, the IRON losses ALSO remain constant.

Discussion

40.	Identify the correct order for the voltage transformation for the three-phase transformers.(a) D-Y > D-D = Y-Y > Y-D(b) D-Y > D-D > Y-Y > Y-D(c) D-Y > D-D = Y-Y < Y-D(d) D-Y > D-D < Y-Y < Y-DI had been asked this question by my school teacher while I was bunking the class.I'm obligated to ask this question of Parallel Operation of Single Phase Transformers topic in division Transformers of Electrical Machines
Answer» Right OPTION is (a) D-Y > D-D = Y-Y > Y-D To explain: DELTA to STAR has maximum(173%) VOLTAGE transformation while star to delta is least(57%). Y-Y and D-D have DEVIATION of voltage levels.

Discussion

41.	For a star-delta three phase transformer, if the transformation ratio is ‘x:1’, then how much percent of output will be?(a) 73%(b) 57%(c) 173%(d) 157%The question was asked during an interview for a job.This is a very interesting question from Parallel Operation of Single Phase Transformers topic in portion Transformers of Electrical Machines
Answer» Right answer is (c) 173% EXPLANATION: LINE VOLTAGE in the output will be (V/1.73*X).

Discussion

42.	For a delta-star three phase transformer, if the transformation ratio is ‘x:1’, then how much percent of output will be improved?(a) 73%(b) 57%(c) 173%(d) 157%I have been asked this question in final exam.My question comes from Parallel Operation of Single Phase Transformers topic in chapter Transformers of Electrical Machines
Answer» The correct OPTION is (a) 73% The best explanation: LINE voltage in the OUTPUT will be (1.73V/x), so the additional voltage will be (173-100/100)100% = 73%.

Discussion

43.	In three phase supply, the voltage phases are displaced by ________ and in two phase by ___________(a) 120°, 90°(b) 180°, 90°(c) 120, 120°(d) 120°, 180°This question was addressed to me by my college director while I was bunking the class.The question is from Parallel Operation of Single Phase Transformers topic in portion Transformers of Electrical Machines
Answer» Correct option is (a) 120°, 90° For EXPLANATION: DISPLACEMENT angle for m-phase SYSTEM is 2*pi/m.

Discussion

44.	Operating transformers in parallel gives the advantage of ___________(a) reliable loading(b) increased capacity of power system(c) reducing the capacity of substation(d) all of the mentionedThe question was asked during an online interview.My question comes from Parallel Operation of Single Phase Transformers topic in chapter Transformers of Electrical Machines
Answer» Right ANSWER is (d) all of the mentioned Explanation: All are advantages of having PARALLEL CONNECTION of transformers.

Discussion

45.	Two single phase transformers A and B are operating in parallel having different impedance and identical x/r ratio. Impedance of A is Za and impedance of B is Zb, both sharing a load of Sl. Then the load shared by transformer B is?(a) Sl(Zb/(Za+Zb))(b) Sl(Za/(Za+Zb))(c) Sl(ZbZa/(Za+Zb))(d) Sl*(Zb+Za/Zb))The question was asked during an interview.I'm obligated to ask this question of Parallel Operation of Single Phase Transformers topic in chapter Transformers of Electrical Machines
Answer» The correct ANSWER is (b) Sl*(Za/(Za+Zb)) The best explanation: The load sharing is BASED on the INVERSE of thekVA RATING.

Discussion

46.	Two single phase transformers A and B are operating in parallel having different impedance and identical x/r ratio. Impedance of A is Za and impedance of B is Zb, both sharing a load of Sl. Then the load shared by transformer A is?(a) Sl(Zb/(Za+Zb))(b) Sl(Za/(Za+Zb))(c) Sl(ZbZa/(Za+Zb))(d) Sl*(Zb+Za/Zb))This question was posed to me in an online quiz.The origin of the question is Parallel Operation of Single Phase Transformers in chapter Transformers of Electrical Machines
Answer» The correct option is (a) Sl*(Zb/(Za+Zb)) The best EXPLANATION: The load SHARING is BASED on the inverse of the KVA RATING.

Discussion

47.	Two single phase transformers A and B are operating in parallel having different impedance and identical x/r ratio. Also impedance of A is more than that of B, then?(a) Za/Zb= Sb/Sa(b) Za/Zb= Sa/Sb(c) Za/Zb= 1(d) Za/Zb= (Sb/Sa)^2I have been asked this question by my college professor while I was bunking the class.The doubt is from Parallel Operation of Single Phase Transformers in chapter Transformers of Electrical Machines
Answer» CORRECT ANSWER is (a) Za/Zb= Sb/Sa Easiest explanation: Leakage IMPEDANCE in ‘OHMS’ are INVERSE ratio of their respective kVA ratings.

Discussion

48.	Two single phase transformers A and B are operating in parallel having different impedance and identical x/r ratio. Also impedance of A is more than that of B, then A ___________(a) shares lesser kVA(b) share more kVA(c) equal kVA as of B(d) total kVAI had been asked this question in an internship interview.This is a very interesting question from Parallel Operation of Single Phase Transformers topic in section Transformers of Electrical Machines
Answer» The correct choice is (a) shares LESSER kVA Explanation: GIVEN that, za is more than ZB, so Ia will be lesser than Ib, With EA = Eb, kVA(A) shared by A will more than kVA(B).

Discussion

49.	Two single phase transformers A and B are operating in parallel having different impedance and identical x/r ratio. Then?(a) A has poorer pf than B(b) B has poorer pf than B(c) lesser power factor angle(d) both operate at same power factorI got this question in a national level competition.My query is from Parallel Operation of Single Phase Transformers topic in chapter Transformers of Electrical Machines
Answer» Correct OPTION is (d) both OPERATE at same power factor Easiest EXPLANATION: As the x/r is same, this supports that they should have same LEAKAGE impedance angles.

Discussion

50.	Two single phase transformers A and B are operating in parallel having same impedance. But the x/r ratio of them are not equal and xa > xb. Then?(a) A has poorer pf than B(b) B has poorer pf than B(c) lesser power factor angle(d) both operate at same power factorI got this question in unit test.I'm obligated to ask this question of Parallel Operation of Single Phase Transformers in chapter Transformers of Electrical Machines
Answer» RIGHT choice is (a) A has POORER pf than B To EXPLAIN I would say: As xa > xb, leakage impedance angle of A will be more than that of B, so lesser power FACTOR.

Discussion

Explore topic-wise InterviewSolutions in .

The voltage regulation fortransformer is given by ___________(a) (E2-V2)/E2(b) (E2-V2)/V2(c) (V2-E2)/E2(d) (V2-E2)/V2The question was posed to me in semester exam.I need to ask this question from Voltage Regulation of Transformer in section Transformers of Electrical Machines

Shape of emf generated by delta connected transformer is not always sinusoidal.(a) True(b) FalseI got this question in semester exam.This intriguing question originated from Three Phase Transformers in chapter Transformers of Electrical Machines

If one of the transformers is removed from the bank of only delta-delta, then it behaves with 58% power delivery.(a) True(b) FalseThe question was posed to me at a job interview.My doubt stems from Three Phase Transformers topic in portion Transformers of Electrical Machines

Open delta transformers can be obtained from ___________(a) delta-delta(b) star-delta(c) delta-star(d) any of the mentionedThe question was posed to me by my college director while I was bunking the class.My doubt stems from Three Phase Transformers in portion Transformers of Electrical Machines

The delta-delta connections are used in applications of ___________(a) large l.v. transformers(b) small h.v. transformers(c) large h.v. transformers(d) small l.v. transformersI got this question in semester exam.Query is from Three Phase Transformers in section Transformers of Electrical Machines

The voltage across the terminal ‘r’ and ‘y’ is?(a) 1.73*V(b) V/1.73(c) V(d) 3*VI got this question during an interview for a job.This intriguing question comes from Three Phase Transformers topic in chapter Transformers of Electrical Machines

For the given circuit below, the voltage across the terminal ‘a’ and ‘b’ is?(a) 1.73*V(b) V/1.73(c) V(d) 3*VI had been asked this question by my college professor while I was bunking the class.My question is based upon Three Phase Transformers in section Transformers of Electrical Machines

The transformer which is more feasible to use in the distribution ends should be ___________(a) star-delta(b) delta-star(c) scott(d) delta-deltaI got this question during an online exam.The question is from Three Phase Transformers topic in division Transformers of Electrical Machines

The voltage conversion ratio of the transformer is inverse of the current transformation.(a) True(b) FalseThe question was posed to me in quiz.This intriguing question originated from Transformer as a Magnetically Coupled Circuit topic in chapter Transformers of Electrical Machines

The voltage across the terminal ‘r’ and ‘y’ is?(a) 1.73V(b) V/1.73(c) V(d) 3VI got this question during an interview for a job.This intriguing question comes from Three Phase Transformers topic in chapter Transformers of Electrical Machines

For the given circuit below, the voltage across the terminal ‘a’ and ‘b’ is?(a) 1.73V(b) V/1.73(c) V(d) 3VI had been asked this question by my college professor while I was bunking the class.My question is based upon Three Phase Transformers in section Transformers of Electrical Machines