43 + Interview Questions in Rating And Loss Dissipation in Electrical Machines Page 1 InterviewSolution

1.	The hydroelectric plants in the industry are best suited to ____________(a) closed circuit air cooling(b) hydrogen gas(c) direct water(d) any of the mentionedThis question was posed to me in semester exam.This intriguing question originated from Cooling (Loss Dissipation) topic in division Rating and Loss Dissipation of Electrical Machines
Answer» Right answer is (a) closed CIRCUIT air COOLING To elaborate: The closed circuit is so used to REUSE the air in the system so that to SAVE water again in the cooling system.

Discussion

2.	The iron losses in a saturated three phase alternator is lesser than the non-saturated three phase alternator.(a) True(b) FalseI got this question in class test.My question comes from Cooling (Loss Dissipation) topic in section Rating and Loss Dissipation of Electrical Machines
Answer» The CORRECT ANSWER is (a) True To explain: The non-saturated reactance is GREATER than saturated reactance. So the reactive losses or iron losses will REDUCE due lesser CONTRIBUTION of the same.

Discussion

3.	A peaky voltage supply is given to the 3 phase power transformer of the connection power system. These results into ____________(a) reduction in iron losses(b) reduction in copper losses(c) increase in iron losses(d) reduction in noiseThe question was asked in an online interview.My doubt stems from Cooling (Loss Dissipation) topic in section Rating and Loss Dissipation of Electrical Machines
Answer» The CORRECT choice is (a) reduction in iron losses Easiest explanation: The flux wave will be SINUSOIDAL in nature as the emf is peaky in nature. Sine wave has LEAST losses when COMPARED to other wave FORMS.

Discussion

4.	A three phase induction motor is connected to the infinite bus operating at the normal conditions. There occurs an unbalancing in the supply, leading to ____________(a) unequal heating losses(b) stopping of motor(c) increase in lower(d) none of the mentionedThis question was posed to me at a job interview.Asked question is from Cooling (Loss Dissipation) in portion Rating and Loss Dissipation of Electrical Machines
Answer» RIGHT answer is (a) unequal heating losses To elaborate: The unbalancing in the SUPPLY phase will create an UNBALANCED distribution of the current in the PHASES, thereby unequal heating.

Discussion

5.	If one of the phases of the supply breaks down, then the connected three phase induction motor ____________(a) continues to run as a single phase induction motor, provided load does does not increase beyond 57.7%(b) stops operating after few seconds(c) continues to run as single phase induction motor(d) continues to run as two phase induction motorI got this question during an interview.Asked question is from Cooling (Loss Dissipation) in chapter Rating and Loss Dissipation of Electrical Machines
Answer» Right OPTION is (a) continues to run as a single phase induction MOTOR, PROVIDED load does does not increase BEYOND 57.7% To elaborate: When one of the phases breaks down then the other two phases will supply the RATED current but the load should be reduced to 57.7%.

Discussion

6.	If one of the phases of RYB supply gets broken, then the temperature rise of the induction motor ____________(a) remains same as before(b) reduces as compared to the normal operating temperature(c) reduces to temperature rise of corresponding single phase induction motor(d) increasesThe question was posed to me in exam.I'd like to ask this question from Cooling (Loss Dissipation) topic in division Rating and Loss Dissipation of Electrical Machines
Answer» Right choice is (a) remains same as before The explanation: The current FLOWING in the ARMATURE will REMAIN same so to MAINTAIN the flux requirements of the machine.Hence the temperature rise will also remain same as the current remains same.

Discussion

7.	For squirrel cage and slip ring induction motor, cooling methods is efficient in ____________(a) squirrel cage induction motor(b) slip ring induction motor(c) both of the motors(d) none of the mentionedI got this question by my college director while I was bunking the class.Origin of the question is Cooling (Loss Dissipation) topic in portion Rating and Loss Dissipation of Electrical Machines
Answer» Right option is (a) SQUIRREL CAGE INDUCTION motor Explanation: As the squirrel cage induction motor has more ventilation and more space as compares to SLIP ring induction motor, there will be more efficient ways to cool down the squirrel cage motor.

Discussion

8.	In dc machine iron losses cause ____________(a) heating in core(b) loss in efficiency(c) rise in temperature of ventilating air(d) all of the mentionedThe question was posed to me during an online exam.My question is from Cooling (Loss Dissipation) in chapter Rating and Loss Dissipation of Electrical Machines
Answer» The CORRECT option is (a) heating in core Easiest explanation: The IRON losses cause heating of the core which CAUSES reduction INEFFICIENCY and cooling AIR gets heated up.

Discussion

9.	If two series motors are identically coupled. One is running as motor while other as generator. For this combination, the iron losses and frictional losses are found identical for ____________(a) identical speed and excitation(b) identical speed(c) identical rating and construction(d) none of the mentionedThe question was posed to me by my school teacher while I was bunking the class.Question is from Cooling (Loss Dissipation) in section Rating and Loss Dissipation of Electrical Machines
Answer» Correct answer is (a) IDENTICAL SPEED and excitation The explanation is: For same iron and frictional losses, same frequency should be there. For that same speed MUST be run.

Discussion

10.	For the given traction application using a dc series motor for a starting time ’t’ is applied. If this method is replaced by a series-parallel control, giving 50% time for each series and parallel. The saving in the starting energy of ____________(a) 25%(b) zero(c) 50%(d) 75%I got this question in a job interview.I need to ask this question from Cooling (Loss Dissipation) topic in portion Rating and Loss Dissipation of Electrical Machines
Answer» Right choice is (a) 25% The best I can explain: Initially LET the energy UTILIZED was 100% for time t.Then for 50% duration for SERIES, energy used is 50%. For PARALLEL OPERATION for the same circuit, the resistance gets halved assuming the same machine. So, for 50% of the parallel operation, 25% of energy is only utilized. Hence total saving is 25%.

Discussion

11.	In the lab, two students X and Y conducted the experiments to verify the name plate ratings of the transformer.But student X conducted the same at higher frequency. The kVA reading of student X will be ___________(a) higher than Y’s reading(b) lower than Y’s reading(c) same as Y’s reading(d) none of the mentionedThis question was posed to me in an interview.The doubt is from Machine Ratings topic in division Rating and Loss Dissipation of Electrical Machines
Answer» CORRECT answer is (a) HIGHER than Y’s reading To ELABORATE: As rating is directly proportional to the frequency of OPERATION.

Discussion

12.	Auto transformer rating is chosen so as to have best performance when the analogous two winding transformer has ___________(a) two voltage levels fairly close to each other(b) very high transformation ratio(c) any voltage levels(d) step down purposeThe question was asked at a job interview.I would like to ask this question from Machine Ratings topic in division Rating and Loss Dissipation of Electrical Machines
Answer» The correct answer is (a) two VOLTAGE LEVELS fairly close to each other The EXPLANATION: The auto transformer is BEST suited with the voltage levels of same rating for a two WINDING transformer.

Discussion

13.	A 200V, 10 hp, 4 poles, 60 Hz, Y-connected induction motor had full load slip of 5%. Then the rotor speed of the motor with respect to stator is?(a) 1710 rpm(b) 1800 rpm(c) 90 rpm(d) 3510 rpmI have been asked this question by my school principal while I was bunking the class.The origin of the question is Machine Ratings topic in section Rating and Loss Dissipation of Electrical Machines
Answer» The correct answer is (a) 1710 RPM For explanation: Synchronous SPEED, Ns = 120f/P = 12060/4 = 1800 rpm Rotor speed = (1-slip)Ns = 0.951800 = 1710 rpm.

Discussion

14.	If two alternators A and B are operated in parallel having per unit synchronous reactance as 0.02 ohms and 0.05 ohms respectively.Then what the ratio of contributing loading of machine A to B?(a) 2.5(b) 0.4(c) 1(d) can not be operated in parallelI had been asked this question in an interview for job.This is a very interesting question from Machine Ratings topic in chapter Rating and Loss Dissipation of Electrical Machines
Answer» The CORRECT answer is (a) 2.5 Best explanation: The load shared by the ALTERNATORS is inversely RELATED to their pu REACTANCE.

Discussion

15.	For a separately excited dc machine of 25 kW, 250 V and armature resistance of 0.25 ohms, is running at 3000 rpm with supply of 255 V. The electromagnetic power produced at the armature in kilo watts is?(a) 5(b) 10(c) 0.5(d) 8I had been asked this question in an international level competition.The origin of the question is Machine Ratings in chapter Rating and Loss Dissipation of Electrical Machines
Answer» The correct OPTION is (a) 5 The BEST explanation: The current in armature, Ia = 255-250/0.25 = 20 A Power = EBIa = 25020 = 5000 W.

Discussion

16.	A 3-phase, five limbed shell type transformer, star connected, 200V, 50 Hz, 100 kVA will have ___________(a) no third harmonic current in its phase but has sinusoidal flux(b) third harmonic current in its phase but has flat-topped flux(c) no third harmonic current in its phase but has flat-topped flux(d) third harmonic current in its phase but has sinusoidal fluxI had been asked this question in semester exam.This interesting question is from Machine Ratings in division Rating and Loss Dissipation of Electrical Machines
Answer» Correct answer is (a) no third harmonic CURRENT in its phase but has sinusoidal flux Explanation: Star connection in three phase has no CLOSED PATH for the FLOW of the third harmonic current.

Discussion

17.	While conducting lab experiments on DC machine loading, the students are given a machine with its rating as 100 kW maximum rating. Then the _____________(a) machine can’t be overloaded after 100 kW(b) machine can be overloaded after 100 kW(c) machine can be overloaded by 5% for a small time duration(d) machine can be overloaded by 10%The question was asked by my school teacher while I was bunking the class.I want to ask this question from Machine Ratings in portion Rating and Loss Dissipation of Electrical Machines
Answer» The correct choice is (a) machine can’t be overloaded after 100 kW The explanation: As the MAXIMUM rating is SPECIFIED and OPERATION CONDITION are also same, it cannot be overloaded beyond the maximum.

Discussion

18.	The desired voltage regulation for a single phase, 50 Hz transformer is zero. Its pu ohmic drop is 4% and pu reactive drop is 4%. The required power factor angle for the operation in degrees is?(a) 45(b) 90(c) 30(d) 60I have been asked this question during a job interview.This is a very interesting question from Machine Ratings topic in chapter Rating and Loss Dissipation of Electrical Machines
Answer» Correct OPTION is (a) 45 The best I can explain: The power factor angle is, tan(PHI)=pu RESISTIVE drop/pu reactive drop = 4/4 = 1.

Discussion

19.	For a single phase, 50 Hz transformer, if the open circuit test is conducted at 40 Hz. What is the variation in the no-load power factor of the transformer?(a) Decreases(b) Increases(c) Remains constant(d) None of the mentionedI had been asked this question during an online exam.I want to ask this question from Machine Ratings topic in chapter Rating and Loss Dissipation of Electrical Machines
Answer» Correct answer is (a) Decreases Best explanation: If the frequency reduces then FLUX density INCREASES, so the flux and then the MAGNETIZING current. When magnetizing current increases power factor angle increases so the power factor decreases.

Discussion

20.	If the dimension of a single phase transformer is made sqrt(3) times less than the original structure, then what is new no load current rating of the transformer?(a) 1/sqrt(3)(b) sqrt(3)(c) 3(d) 1/3*sqrt(3)This question was addressed to me during an interview.This intriguing question originated from Machine Ratings in division Rating and Loss Dissipation of Electrical Machines
Answer» Correct option is (a) 1/sqrt(3) Explanation: The no load current of the TRANSFORMER is DIRECTLY proportional to the dimension of the transformer.

Discussion

21.	Refer the diagram; a single-phase supply of 100V, 50Hz is fed to the step-up transformer having primary impedance of 1 ohms and secondary impedance 20 ohms. What is the power consumed by the load of 5 ohms?(a) 20 W(b) 40 W(c) 10 W(d) 100 WI got this question during an online interview.The above asked question is from Machine Ratings topic in division Rating and Loss Dissipation of Electrical Machines
Answer» The correct OPTION is (a) 20 W For explanation I WOULD say: The REFERRED resistance to the secondary, Z2=1(5^2) = 25 ohms Total resistance at secondary = 25+20 = 45 ohms Total resistance seen by source = 45+5 = 50 ohms Hence, CURRENT in secondary = 100/50 = 2 A Power consumed by the LOAD = I^2 R = 4*5 = 20 W.

Discussion

22.	No load rotational losses in electrical machine consists of _____________(a) Friction and windage losses(b) Stator core, friction and windage losses(c) Rotor core, friction and windage losses(d) No load core, friction and windage lossesThe question was posed to me in final exam.Question is from Losses and Efficiency in division Rating and Loss Dissipation of Electrical Machines
Answer» Right ANSWER is (d) No load CORE, friction and WINDAGE losses To explain: The sum of friction and windage LOSS under no load is called no load rotational losses.

Discussion

23.	For the same rating machines, which of the following statement is correct regarding the efficiency (η)?(a) η of low speed machine > η of high speed machine(b) η of low speed machine < η of high speed machine(c) η of low speed machine = η of high speed machine(d) Any of the mentionedThis question was addressed to me in final exam.My doubt is from Losses and Efficiency in portion Rating and Loss Dissipation of Electrical Machines
Answer» Right OPTION is (b) η of low speed MACHINE < η of high speed machine For explanation I would SAY: The amount of CONDUCTOR and iron MATERIALS required for a machine of given rating is inversely proportional to its speed. Also, more iron and conductor would entail more losses.

Discussion

24.	The electromechanical energy conversion devices used in power systems are never operated to deliver maximum power output because at maximum power output _____________(a) Efficiency is less than 50%(b) Temperature of the power devices is much more than the specified allowable temperature rise(c) Half of the power input appears as losses(d) Any of the mentionedI got this question in an interview for internship.Query is from Losses and Efficiency topic in portion Rating and Loss Dissipation of Electrical Machines
Answer» Correct answer is (b) Temperature of the power devices is much more than the SPECIFIED ALLOWABLE temperature rise Easiest explanation: In practice, devices are operated at a LOAD somewhat less than rated load, at which the efficiency is MAXIMUM.

Discussion

25.	Which of the given losses are directly proportional to square of speed?(a) Windage loss(b) Eddy current loss(c) Both Windage and eddy current loss(d) Hysteresis loss and brush lossThis question was posed to me by my school principal while I was bunking the class.The doubt is from Losses and Efficiency in division Rating and Loss Dissipation of Electrical Machines
Answer» RIGHT answer is (c) Both Windage and eddy current loss To elaborate: The windage loss includes the power required to CIRCULATE air through the machine and ventilating ducts, and is approximately PROPORTIONAL to the square of speed. ALSO, eddy current losses are proportional to square of speed.

Discussion

26.	What percentage of the rated output for DC machine and synchronous machine is taken as stray load losses respectively?(a) 1% and 0.5%(b) 0.5% and 1%(c) 3% and 0.1%(d) 0.1% and 5%The question was asked during an interview for a job.The origin of the question is Losses and Efficiency topic in chapter Rating and Loss Dissipation of Electrical Machines
Answer» RIGHT choice is (a) 1% and 0.5% To elaborate: Stray load LOSSES cannot be determined accurately. In DC machine, by convention, it is taken as 1% of the rated output for rating above 150 KW. For SYNCHRONOUS and induction machine, it is taken as 0.5% of their rated output.

Discussion

27.	The pole shoes in DC and synchronous machines are laminated to reduce _____________(a) Resistance losses(b) Pulsation or pole-face losses(c) Mechanical losses(d) None of the mentionedI have been asked this question during an internship interview.I would like to ask this question from Losses and Efficiency topic in portion Rating and Loss Dissipation of Electrical Machines
Answer»

Discussion

28.	In an induction motor, which of the following is correct?(a) Stator core loss < rotor core loss(b) Stator core loss = rotor core loss(c) Stator core loss > rotor core loss(d) Any of the mentionedThe question was posed to me in an interview for job.This is a very interesting question from Losses and Efficiency topic in section Rating and Loss Dissipation of Electrical Machines
Answer» Correct OPTION is (c) Stator core loss > rotor core loss To explain I would say: The rotor core loss is almost NEGLIGIBLE because of REDUCED frequency of the FLUX reversals (equal to slip frequency, sf) in the rotor, and Pe∝f^2 and Ph∝f. (Pe = eddy current losses,Ph = HYSTERESIS losses).

Discussion

29.	The usual lamination thickness selected to minimize the eddy current loss in rotor is _____________(a) 0.1 mm to 0.2 mm(b) 0.3 mm to 0.4 mm(c) 0.4 mm to 0.5 mm(d) 0.9 mm to 0.10 mmThe question was posed to me by my school principal while I was bunking the class.My enquiry is from Losses and Efficiency topic in portion Rating and Loss Dissipation of Electrical Machines
Answer» Correct answer is (c) 0.4 mm to 0.5 mm The BEST I can explain: If lamination thickness is made less than 0.4 mm, the reduction in eddy CURRENT losses is achieved, but at the COST of ADDITIONAL labor charges in assembling the rotor.

Discussion

30.	In rotating electrical machines, when the armature rotates, there are continuous magnetic reversals and power required for their reversals is called _____________(a) Eddy current loss(b) Hysteresis loss(c) Resistance or ohmic losses(d) Mechanical lossI have been asked this question in quiz.Enquiry is from Losses and Efficiency topic in chapter Rating and Loss Dissipation of Electrical Machines
Answer» The correct ANSWER is (b) Hysteresis LOSS To elaborate: Hysteresis loss is DIRECTLY proportional to the number of magnetic reversals per second or the SPEED.

Discussion

31.	Which of the following statements are correct regarding brush contact losses?(a) In DC machine: proportional to armature current(b) In synchronous machine: neglected(c) In induction machine: neglected(d) Any of the mentionedThe question was posed to me by my college director while I was bunking the class.This intriguing question comes from Losses and Efficiency in division Rating and Loss Dissipation of Electrical Machines
Answer»

Discussion

32.	To determine the efficiency of the machine, direct load test is not advantageous because of which of the following reasons?(a) Cost of providing large inputs(b) Difficulty of dissipating the large outputs(c) Both cost of providing large inputs and difficulty in dissipating the large outputs(d) None of the mentionedI have been asked this question in an internship interview.This intriguing question comes from Losses and Efficiency in section Rating and Loss Dissipation of Electrical Machines
Answer» Right CHOICE is (c) Both cost of PROVIDING large inputs and difficulty in dissipating the large outputs The explanation is: Also, a small error in the measurement of either output or INPUT causes the same AMOUNT of error in the COMPUTED efficiency.

Discussion

33.	A consideration of the power losses in electrical machines is essential for which of the following reasons?(a) Operating cost(b) Temperature rise(c) Voltage drops(d) All of the mentionedI got this question in an international level competition.I'm obligated to ask this question of Losses and Efficiency in section Rating and Loss Dissipation of Electrical Machines
Answer» Right choice is (d) All of the mentioned The best I can explain: A MACHINE with lower EFFICIENCY has more losses, and therefore increased OPERATING cost. Also, losses cause heating of the machine and therefore, its temperature rise. Similarly, voltage drop IR is associated with OHMIC loss.

Discussion

34.	A peaky voltage supply is given to the 3 phase power transformer of the connection power system. These results in _________(a) reduction in iron losses(b) reduction in copper losses(c) increase in iron losses(d) reduction in noiseThe question was posed to me at a job interview.My doubt is from Losses and Efficiency in chapter Rating and Loss Dissipation of Electrical Machines
Answer» CORRECT choice is (a) reduction in iron losses To elaborate: The flux WAVE will be sinusoidal in nature as the EMF is peaky in nature. Sine wave has LEAST losses when COMPARED to other wave forms.

Discussion

35.	The hydroelectric plants in the industry are best suited with _________(a) closed circuit air cooling(b) hydrogen gas(c) direct water(d) all of the mentionedI have been asked this question in an interview for job.My doubt is from Losses and Efficiency in division Rating and Loss Dissipation of Electrical Machines
Answer» Right OPTION is (a) CLOSED CIRCUIT AIR cooling The best I can explain: The closed circuit is so used to REUSE the air in the system so that to save water again in the cooling system.

Discussion

36.	A three phase induction motor is connected to the infinite bus operating at the normal conditions. There occurs an unbalancing in the supply, leading to _________(a) unequal heating losses(b) stopping of motor(c) increase in lower(d) none of the mentionedThis question was addressed to me during an online exam.I'd like to ask this question from Losses and Efficiency topic in section Rating and Loss Dissipation of Electrical Machines
Answer» CORRECT OPTION is (a) unequal heating losses The best I can explain: The UNBALANCING in the supply PHASE will create an unbalanced distribution of the current in the phases, thereby unequal heating.

Discussion

37.	If one of the phases of RYB supply gets broken, then the temperature rise of the induction motor _________(a) remains same as before(b) reduces as compared to the normal operating temperature(c) reduces to temperature rise of corresponding single phase induction motor(d) increasesI got this question during an online interview.The origin of the question is Losses and Efficiency topic in section Rating and Loss Dissipation of Electrical Machines
Answer» Correct ANSWER is (a) remains same as before The explanation is: The current flowing in the armature will REMAIN same so to maintain the FLUX requirements of the machine. HENCE the temperature rise will also remain same as the current remains same.

Discussion

38.	If one of the phases of the supply breaks down, then the connected three phase induction motor _________(a) continues to run as a single phase induction motor, provided load does does not increase beyond 57.7%(b) stops operating after few seconds(c) continues to run as single phase induction motor(d) continues to run as two phase induction motorI had been asked this question in a job interview.The above asked question is from Losses and Efficiency topic in portion Rating and Loss Dissipation of Electrical Machines
Answer» Correct answer is (a) CONTINUES to run as a single phase induction motor, provided load does does not increase BEYOND 57.7% Easy explanation: When one of the PHASES breaks down then the other two phases will SUPPLY the rated current but the load should be reduced to 57.7%.

Discussion

39.	For squirrel cage and slip ring induction motor, cooling methods is efficient in _________(a) squirrel cage induction motor(b) slip ring induction motor(c) both of the motors(d) none of the mentionedI got this question in final exam.This is a very interesting question from Losses and Efficiency in chapter Rating and Loss Dissipation of Electrical Machines
Answer» The correct option is (a) SQUIRREL cage induction motor Easiest explanation: As the squirrel cage induction motor has more VENTILATION and more space as compares to slip ring induction motor, there will be more efficient WAYS to COOL down the squirrel cage motor.

Discussion

40.	In dc machine iron losses cause _________(a) heating in core(b) loss in efficiency(c) rise in temperature of ventilating air(d) all of the mentionedThis question was addressed to me during an interview.I'd like to ask this question from Losses and Efficiency in chapter Rating and Loss Dissipation of Electrical Machines
Answer» Right choice is (a) heating in CORE Best explanation: The iron losses cause heating of the core which CAUSES REDUCTION inefficiency and cooling air GETS heated up.

Discussion

41.	Hysteresis loss in a dc machine is _____ of rate of flow of air and _____ on frequency of _____(a) independent, dependent, magnetic reversal(b) independent, dependent, operation(c) dependent, independent, magnetic reversal(d) none of the mentionedThis question was posed to me at a job interview.Question is taken from Losses and Efficiency in chapter Rating and Loss Dissipation of Electrical Machines
Answer» The correct answer is (a) independent, dependent, magnetic reversal To explain: Hysteresis LOSS in a DC machine is independent of RATE of flow of air and DEPENDS on frequency of magnetic reversal.

Discussion

42.	If two series motors are identically coupled. One is running as motor while other as generator. For this combination, the iron losses and frictional losses are found identical for _________(a) identical speed and excitation(b) identical speed(c) identical rating and construction(d) none of the mentionedThis question was addressed to me by my college professor while I was bunking the class.This question is from Losses and Efficiency in portion Rating and Loss Dissipation of Electrical Machines
Answer» RIGHT choice is (a) IDENTICAL speed and excitation To elaborate: For same iron and FRICTIONAL losses, same frequency should be there. For that same speed must be RUN.

Discussion

43.	For the given traction application using a dc series motor for a starting time ’t’ is applied. If this method is replaced by a series-parallel control, giving 50% time for each series and parallel. The saving in the starting energy of _________(a) 25%(b) zero(c) 50%(d) 75%I got this question in quiz.The query is from Losses and Efficiency in portion Rating and Loss Dissipation of Electrical Machines
Answer» Right option is (a) 25% The EXPLANATION is: Initially let the energy utilized was 100% for time t.Then for 50% duration for SERIES, energy USED is 50%. For PARALLEL operation for the same circuit, the resistance gets halved assuming the same machine. So, for 50% of the parallel operation, 25% of energy is only utilized. Hence total saving is 25%.

Discussion

Explore topic-wise InterviewSolutions in .

The iron losses in a saturated three phase alternator is lesser than the non-saturated three phase alternator.(a) True(b) FalseI got this question in class test.My question comes from Cooling (Loss Dissipation) topic in section Rating and Loss Dissipation of Electrical Machines