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A 200 V shunt motor with shunt resistance of 40 Ω and armature resistance of 0.02 Ω takes a current of 55 A and runs at 850 rpm, when there is a resistance of 0.58 Ω in series with, armature.
Q.
Torque remaining the same, to raise the speed to 750 rpm the resistance to be added in armature is ______
- a)0.6 Ω
- b)0.1 Ω
- c)0.4 Ω
- d)0.2 Ω
Correct answer is option 'C'. Can you explain this answer?
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A 200 V shunt motor with shunt resistance of 40 Ω and armature re...
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Solution:
Given parameters are:
V = 200 V
Ra = 0.02
Ia = 55 A
N1 = 850 rpm
Rsh = 40
N2 = 750 rpm
Ra2 = ?
Torque in a DC shunt motor is given by:
T ∝ φ Ia
Where, φ = V / (Ra + Rsh)
So, T ∝ (V / (Ra + Rsh)) Ia
From the above equation, we can infer that torque is directly proportional to flux, armature current, and inversely proportional to the sum of armature and shunt resistance.
Now, to maintain the torque, we need to keep the product of flux and armature current constant.
So, (V / (Ra + Rsh)) Ia = (V / (Ra2 + Rsh)) Ia2
Where, Ia2 is the armature current at 750 rpm.
From the above equation, we can write:
Ra2 = (V / Ia2) - Rsh
To calculate Ia2, we can use the speed equation of a DC shunt motor given by:
N ∝ ((V - Ia Ra) / φ)
So, (N1 / N2) = ((V - Ia Ra) / φ) / ((V - Ia2 Ra2) / φ)
Substituting the given values, we get:
(850 / 750) = ((200 - 55 × 0.02) / (200 / (0.02 + 40))) / ((200 - Ia2 Ra2) / (200 / (0.02 + 40)))
Solving the above equation, we get:
Ra2 = 0.4 Ω
Therefore, the resistance to be added in series with the armature to raise the speed to 750 rpm is 0.4 Ω.
Hence, option (C) is the correct answer.
Given parameters are:
V = 200 V
Ra = 0.02
Ia = 55 A
N1 = 850 rpm
Rsh = 40
N2 = 750 rpm
Ra2 = ?
Torque in a DC shunt motor is given by:
T ∝ φ Ia
Where, φ = V / (Ra + Rsh)
So, T ∝ (V / (Ra + Rsh)) Ia
From the above equation, we can infer that torque is directly proportional to flux, armature current, and inversely proportional to the sum of armature and shunt resistance.
Now, to maintain the torque, we need to keep the product of flux and armature current constant.
So, (V / (Ra + Rsh)) Ia = (V / (Ra2 + Rsh)) Ia2
Where, Ia2 is the armature current at 750 rpm.
From the above equation, we can write:
Ra2 = (V / Ia2) - Rsh
To calculate Ia2, we can use the speed equation of a DC shunt motor given by:
N ∝ ((V - Ia Ra) / φ)
So, (N1 / N2) = ((V - Ia Ra) / φ) / ((V - Ia2 Ra2) / φ)
Substituting the given values, we get:
(850 / 750) = ((200 - 55 × 0.02) / (200 / (0.02 + 40))) / ((200 - Ia2 Ra2) / (200 / (0.02 + 40)))
Solving the above equation, we get:
Ra2 = 0.4 Ω
Therefore, the resistance to be added in series with the armature to raise the speed to 750 rpm is 0.4 Ω.
Hence, option (C) is the correct answer.
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Question Description
A 200 V shunt motor with shunt resistance of 40 Ω and armature resistance of 0.02 Ω takes a current of 55 A and runs at 850 rpm, when there is a resistance of 0.58 Ω in series with, armature.Q. Torque remaining the same, to raise the speed to 750 rpm the resistance to be added in armature is ______a)0.6 Ω b)0.1 Ωc)0.4 Ω d)0.2 ΩCorrect answer is option 'C'. Can you explain this answer? for Electrical Engineering (EE) 2026 is part of Electrical Engineering (EE) preparation. The Question and answers have been prepared according to the Electrical Engineering (EE) exam syllabus. Information about A 200 V shunt motor with shunt resistance of 40 Ω and armature resistance of 0.02 Ω takes a current of 55 A and runs at 850 rpm, when there is a resistance of 0.58 Ω in series with, armature.Q. Torque remaining the same, to raise the speed to 750 rpm the resistance to be added in armature is ______a)0.6 Ω b)0.1 Ωc)0.4 Ω d)0.2 ΩCorrect answer is option 'C'. Can you explain this answer? covers all topics & solutions for Electrical Engineering (EE) 2026 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for A 200 V shunt motor with shunt resistance of 40 Ω and armature resistance of 0.02 Ω takes a current of 55 A and runs at 850 rpm, when there is a resistance of 0.58 Ω in series with, armature.Q. Torque remaining the same, to raise the speed to 750 rpm the resistance to be added in armature is ______a)0.6 Ω b)0.1 Ωc)0.4 Ω d)0.2 ΩCorrect answer is option 'C'. Can you explain this answer?.
A 200 V shunt motor with shunt resistance of 40 Ω and armature resistance of 0.02 Ω takes a current of 55 A and runs at 850 rpm, when there is a resistance of 0.58 Ω in series with, armature.Q. Torque remaining the same, to raise the speed to 750 rpm the resistance to be added in armature is ______a)0.6 Ω b)0.1 Ωc)0.4 Ω d)0.2 ΩCorrect answer is option 'C'. Can you explain this answer? for Electrical Engineering (EE) 2026 is part of Electrical Engineering (EE) preparation. The Question and answers have been prepared according to the Electrical Engineering (EE) exam syllabus. Information about A 200 V shunt motor with shunt resistance of 40 Ω and armature resistance of 0.02 Ω takes a current of 55 A and runs at 850 rpm, when there is a resistance of 0.58 Ω in series with, armature.Q. Torque remaining the same, to raise the speed to 750 rpm the resistance to be added in armature is ______a)0.6 Ω b)0.1 Ωc)0.4 Ω d)0.2 ΩCorrect answer is option 'C'. Can you explain this answer? covers all topics & solutions for Electrical Engineering (EE) 2026 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for A 200 V shunt motor with shunt resistance of 40 Ω and armature resistance of 0.02 Ω takes a current of 55 A and runs at 850 rpm, when there is a resistance of 0.58 Ω in series with, armature.Q. Torque remaining the same, to raise the speed to 750 rpm the resistance to be added in armature is ______a)0.6 Ω b)0.1 Ωc)0.4 Ω d)0.2 ΩCorrect answer is option 'C'. Can you explain this answer?.
Solutions for A 200 V shunt motor with shunt resistance of 40 Ω and armature resistance of 0.02 Ω takes a current of 55 A and runs at 850 rpm, when there is a resistance of 0.58 Ω in series with, armature.Q. Torque remaining the same, to raise the speed to 750 rpm the resistance to be added in armature is ______a)0.6 Ω b)0.1 Ωc)0.4 Ω d)0.2 ΩCorrect answer is option 'C'. Can you explain this answer? in English & in Hindi are available as part of our courses for Electrical Engineering (EE). Download more important topics, notes, lectures and mock test series for Electrical Engineering (EE) Exam by signing up for free.
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