The self and mutual inductances of a doubly excited magnetic system are Ls=0.6+0.20cos2θr H and Lr=0.75+0.30cos2θr H and Msr=0.8cosθr H. For a stationary rotor at an angular position of θr=60°,what is the magnitude of torque when the currents is=20A DC and ir=10A DC?(a) -233.88N-m(b) +233.88N-m(c) -467.76N-m(d) +467.76N-mI had been asked this question during an interview for a job.My question is from Elementary Synchronous Machines topic in portion Basic Concepts in Rotating Machines of Electrical Machines

The self and mutual inductances of a doubly excited magnetic system ar

1.	The self and mutual inductances of a doubly excited magnetic system are Ls=0.6+0.20cos2θr H and Lr=0.75+0.30cos2θr H and Msr=0.8cosθr H. For a stationary rotor at an angular position of θr=60°,what is the magnitude of torque when the currents is=20A DC and ir=10A DC?(a) -233.88N-m(b) +233.88N-m(c) -467.76N-m(d) +467.76N-mI had been asked this question during an interview for a job.My question is from Elementary Synchronous Machines topic in portion Basic Concepts in Rotating Machines of Electrical Machines
Answer» The correct option is (a) -233.88N-m Best EXPLANATION: For θr=60°; Ls, Lr, Msr and their DERIVATIVES with RESPECT to θr have the FOLLOWING values: Ls=0.50H, Lr=0.60H, Msr=0.40H, dLs/dθr=-0.3464, dLr/dθr=-0.52, dMsr/dθr=-0.693 Substituting the numerical values in TE = 1/2is^2dLs/dθr+1/2ir^2dLr/dθr+isrdMsr/dθr = -233.88N-m.

Discussion

No Comment Found

Related InterviewSolutions

In a doubly excited magnetic systems, the magnetic torques and forces act in such a direction as to tend to ___________(a) decrease the field energy at constant currents(b) decrease the field co-energy at constant currents(c) increase the field energy at constant currents(d) none of the mentionedThe question was posed to me in my homework.This intriguing question comes from Doubly Excited Magnetic Systems topic in portion Basic Concepts in Rotating Machines of Electrical Machines
In a doubly excited magnetic system of salient pole type stator and rotor, the reluctance torque is present only when _____________(a) both stator and rotor currents are acting(b) stator current is acting alone(c) rotor current is acting alone(d) any of the stator or rotor currents acting aloneI have been asked this question in an online interview.My question is from Doubly Excited Magnetic Systems in chapter Basic Concepts in Rotating Machines of Electrical Machines
If φm is the maximum value of flux due to any one phase, then resultant flux in 2 phase and 3 phase AC machines would respectively be given by _________(a) φm and 1.5φm, both rotating(b) φm and 1.5φm, both stand still(c) φm stand still and 1.5φm rotating(d) 1.5φm and 2φm, both rotatingThe question was posed to me in an interview for internship.This question is from Rotating Magnetic Field topic in section Basic Concepts in Rotating Machines of Electrical Machines
In case of the 3 phase winding with delta or star connection without neutral, if one of the supply lines gets disconnected, then the MMF becomes __________(a) Stationary and pulsating(b) Rotating with synchronous speed(c) Rotating with sub synchronous speed(d) Rotating with super synchronous speedI have been asked this question in an internship interview.I need to ask this question from Rotating Magnetic Field in chapter Basic Concepts in Rotating Machines of Electrical Machines
A 3 phase star connected winding is fed from symmetrical 3 phase supply with their neutrals connected together. If one of the 3 supply lines gets disconnected, then the revolving MMF wave will have a ___________(a) Constant amplitude but sub synchronous speed(b) Varying amplitude but synchronous speed(c) Constant amplitude but super synchronous speed(d) Varying speed and a speed fluctuating around the synchronous speedThis question was addressed to me during an interview.I'm obligated to ask this question of Rotating Magnetic Field in chapter Basic Concepts in Rotating Machines of Electrical Machines
The rotating MMF wave of constant amplitude can be produced, only if the time angle displacement between currents is _____________(a) Less than the space angle displacement between winding axis(b) More than the space angle displacement between winding axis(c) Equal to the space angle displacement between winding axis(d) All of the mentionedThis question was addressed to me during an interview.My question is based upon Rotating Magnetic Field topic in portion Basic Concepts in Rotating Machines of Electrical Machines
Three phase voltages are applied to the three windings of an electrical machine. If any two supply terminals are interchanged, then the rotating MMF wave _____________(a) Direction reverses, amplitude alters(b) Direction reverses, amplitude unaltered(c) Direction remains same, amplitude alters(d) Direction remains same, amplitude unalteredI had been asked this question during a job interview.My question is taken from Rotating Magnetic Field in portion Basic Concepts in Rotating Machines of Electrical Machines
What does the space angle α in the equation Fr(α,t)=3/2Fmcos(α-ωt) for MMF produced when 3-phase balanced windings excited by three phase balanced currents represent?(a) MMF wave at any moment is sinusoidally distributed in space(b) Entire MMF waveform is travelling at (constant angular speed) synchronous speed(c) MMF wave is of constant amplitude(d) None of the mentionedI have been asked this question in unit test.I'm obligated to ask this question of Rotating Magnetic Field in chapter Basic Concepts in Rotating Machines of Electrical Machines
When a single-phase winding is excited by an alternating current, then which of the following statements are correct?(a) It produces one stationary MMF wave(b) Produced MMF wave pulsates along its magnetic axis(c) It doesn’t produce two counter rotating MMF wave(d) All of the mentionedI had been asked this question during a job interview.This intriguing question originated from Rotating Magnetic Field topic in portion Basic Concepts in Rotating Machines of Electrical Machines
Which of the following harmonics are present in the resultant MMF produced by 3 phase currents flowing in the 3 phase windings?(a) Triplen harmonics (3K), where K is an integer(b) 6K+1 harmonics only, where K is an integer(c) 6K-1 harmonics only, where K is an integer(d) 6k+1 and 6K-1 harmonics, where K is an integerI had been asked this question in an online quiz.I'd like to ask this question from Rotating Magnetic Field topic in division Basic Concepts in Rotating Machines of Electrical Machines

Discussion

No Comment Found

Related InterviewSolutions

Reply to Comment