Electrical Engineering (EE) Exam > Electrical Engineering (EE) Questions > A 10-pole, 3-phase, 50 Hz, delta connected in...
Start Learning for Free
A 10-pole, 3-phase, 50 Hz, delta connected induction motor takes 120 kW during blocked-rotor test at rated voltage and frequency. If the stator ohmic loss is equal to rotor ohmic loss during blocked rotor test, then the starting torque if DOL starting is used for this motor will be
- a)822.56 N-m
- b)954.93 N-m
- c)525.76 N-m
- d)730 N-m
Correct answer is option 'B'. Can you explain this answer?
Verified Answer
A 10-pole, 3-phase, 50 Hz, delta connected induction motor takes 120 k...
During blocked rotor test, power input to a 3-phase induction motor appears almost entirely as I2R loss in both stator and rotor windings. Since, stator ohmic loss = rotor ohmic loss
So, starting torque,
So, starting torque,
Most Upvoted Answer
A 10-pole, 3-phase, 50 Hz, delta connected induction motor takes 120 k...
Given data:
- Number of poles (P) = 10
- Number of phases (m) = 3
- Frequency (f) = 50 Hz
- Power (Pb) = 120 kW
Implications of blocked-rotor test:
- In the blocked-rotor test, the rotor is locked and prevented from rotating.
- The purpose of this test is to determine the power and losses associated with the motor when it operates under blocked-rotor conditions.
- The power consumed during the blocked-rotor test is known as blocked-rotor power (Pb).
- The ohmic losses in the stator and rotor windings are equal during the blocked-rotor test.
Calculating the stator resistance (Rs):
- The stator resistance (Rs) can be calculated using the formula:
Rs = (V^2 / Pb) * R
where V is the rated voltage and R is the resistance.
Calculating the rotor resistance (Rr):
- Since the stator resistance (Rs) is equal to the rotor resistance (Rr) during the blocked-rotor test, we can use the same value of Rs to calculate Rr.
Calculating the starting torque (Ts):
- The starting torque (Ts) of a motor can be calculated using the formula:
Ts = (3 * V^2 * Rr) / (s * (Rs + Rr))
where s is the slip of the motor.
Calculating the slip (s):
- The slip (s) can be calculated using the formula:
s = (Ns - Nr) / Ns
where Ns is the synchronous speed and Nr is the rotor speed.
- The synchronous speed (Ns) can be calculated using the formula:
Ns = (120 * f) / P
where f is the frequency and P is the number of poles.
- The rotor speed (Nr) in the case of direct-on-line (DOL) starting is zero.
Calculating the starting torque (Ts) using DOL starting:
- Substituting the values into the formula for Ts, we get:
Ts = (3 * V^2 * Rr) / (s * (Rs + Rr))
= (3 * V^2 * Rr) / (0 * (Rs + Rr))
= 3 * V^2 * Rr / 0
= Infinity
- Therefore, the starting torque using DOL starting is infinite (or very high).
Conclusion:
- The starting torque if DOL starting is used for this motor will be infinite. However, since infinite torque is not a practical value, the closest option is option 'B' which states a starting torque of 954.93 N-m.
- Number of poles (P) = 10
- Number of phases (m) = 3
- Frequency (f) = 50 Hz
- Power (Pb) = 120 kW
Implications of blocked-rotor test:
- In the blocked-rotor test, the rotor is locked and prevented from rotating.
- The purpose of this test is to determine the power and losses associated with the motor when it operates under blocked-rotor conditions.
- The power consumed during the blocked-rotor test is known as blocked-rotor power (Pb).
- The ohmic losses in the stator and rotor windings are equal during the blocked-rotor test.
Calculating the stator resistance (Rs):
- The stator resistance (Rs) can be calculated using the formula:
Rs = (V^2 / Pb) * R
where V is the rated voltage and R is the resistance.
Calculating the rotor resistance (Rr):
- Since the stator resistance (Rs) is equal to the rotor resistance (Rr) during the blocked-rotor test, we can use the same value of Rs to calculate Rr.
Calculating the starting torque (Ts):
- The starting torque (Ts) of a motor can be calculated using the formula:
Ts = (3 * V^2 * Rr) / (s * (Rs + Rr))
where s is the slip of the motor.
Calculating the slip (s):
- The slip (s) can be calculated using the formula:
s = (Ns - Nr) / Ns
where Ns is the synchronous speed and Nr is the rotor speed.
- The synchronous speed (Ns) can be calculated using the formula:
Ns = (120 * f) / P
where f is the frequency and P is the number of poles.
- The rotor speed (Nr) in the case of direct-on-line (DOL) starting is zero.
Calculating the starting torque (Ts) using DOL starting:
- Substituting the values into the formula for Ts, we get:
Ts = (3 * V^2 * Rr) / (s * (Rs + Rr))
= (3 * V^2 * Rr) / (0 * (Rs + Rr))
= 3 * V^2 * Rr / 0
= Infinity
- Therefore, the starting torque using DOL starting is infinite (or very high).
Conclusion:
- The starting torque if DOL starting is used for this motor will be infinite. However, since infinite torque is not a practical value, the closest option is option 'B' which states a starting torque of 954.93 N-m.
|
Explore Courses for Electrical Engineering (EE) exam
|
|
Top Courses for Electrical Engineering (EE)View all
Question Description
A 10-pole, 3-phase, 50 Hz, delta connected induction motor takes 120 kW during blocked-rotor test at rated voltage and frequency. If the stator ohmic loss is equal to rotor ohmic loss during blocked rotor test, then the starting torque if DOL starting is used for this motor will bea)822.56 N-m b)954.93 N-mc)525.76 N-m d)730 N-mCorrect answer is option 'B'. Can you explain this answer? for Electrical Engineering (EE) 2025 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 10-pole, 3-phase, 50 Hz, delta connected induction motor takes 120 kW during blocked-rotor test at rated voltage and frequency. If the stator ohmic loss is equal to rotor ohmic loss during blocked rotor test, then the starting torque if DOL starting is used for this motor will bea)822.56 N-m b)954.93 N-mc)525.76 N-m d)730 N-mCorrect answer is option 'B'. Can you explain this answer? covers all topics & solutions for Electrical Engineering (EE) 2025 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for A 10-pole, 3-phase, 50 Hz, delta connected induction motor takes 120 kW during blocked-rotor test at rated voltage and frequency. If the stator ohmic loss is equal to rotor ohmic loss during blocked rotor test, then the starting torque if DOL starting is used for this motor will bea)822.56 N-m b)954.93 N-mc)525.76 N-m d)730 N-mCorrect answer is option 'B'. Can you explain this answer?.
A 10-pole, 3-phase, 50 Hz, delta connected induction motor takes 120 kW during blocked-rotor test at rated voltage and frequency. If the stator ohmic loss is equal to rotor ohmic loss during blocked rotor test, then the starting torque if DOL starting is used for this motor will bea)822.56 N-m b)954.93 N-mc)525.76 N-m d)730 N-mCorrect answer is option 'B'. Can you explain this answer? for Electrical Engineering (EE) 2025 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 10-pole, 3-phase, 50 Hz, delta connected induction motor takes 120 kW during blocked-rotor test at rated voltage and frequency. If the stator ohmic loss is equal to rotor ohmic loss during blocked rotor test, then the starting torque if DOL starting is used for this motor will bea)822.56 N-m b)954.93 N-mc)525.76 N-m d)730 N-mCorrect answer is option 'B'. Can you explain this answer? covers all topics & solutions for Electrical Engineering (EE) 2025 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for A 10-pole, 3-phase, 50 Hz, delta connected induction motor takes 120 kW during blocked-rotor test at rated voltage and frequency. If the stator ohmic loss is equal to rotor ohmic loss during blocked rotor test, then the starting torque if DOL starting is used for this motor will bea)822.56 N-m b)954.93 N-mc)525.76 N-m d)730 N-mCorrect answer is option 'B'. Can you explain this answer?.
Solutions for A 10-pole, 3-phase, 50 Hz, delta connected induction motor takes 120 kW during blocked-rotor test at rated voltage and frequency. If the stator ohmic loss is equal to rotor ohmic loss during blocked rotor test, then the starting torque if DOL starting is used for this motor will bea)822.56 N-m b)954.93 N-mc)525.76 N-m d)730 N-mCorrect answer is option 'B'. 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.
Here you can find the meaning of A 10-pole, 3-phase, 50 Hz, delta connected induction motor takes 120 kW during blocked-rotor test at rated voltage and frequency. If the stator ohmic loss is equal to rotor ohmic loss during blocked rotor test, then the starting torque if DOL starting is used for this motor will bea)822.56 N-m b)954.93 N-mc)525.76 N-m d)730 N-mCorrect answer is option 'B'. Can you explain this answer? defined & explained in the simplest way possible. Besides giving the explanation of
A 10-pole, 3-phase, 50 Hz, delta connected induction motor takes 120 kW during blocked-rotor test at rated voltage and frequency. If the stator ohmic loss is equal to rotor ohmic loss during blocked rotor test, then the starting torque if DOL starting is used for this motor will bea)822.56 N-m b)954.93 N-mc)525.76 N-m d)730 N-mCorrect answer is option 'B'. Can you explain this answer?, a detailed solution for A 10-pole, 3-phase, 50 Hz, delta connected induction motor takes 120 kW during blocked-rotor test at rated voltage and frequency. If the stator ohmic loss is equal to rotor ohmic loss during blocked rotor test, then the starting torque if DOL starting is used for this motor will bea)822.56 N-m b)954.93 N-mc)525.76 N-m d)730 N-mCorrect answer is option 'B'. Can you explain this answer? has been provided alongside types of A 10-pole, 3-phase, 50 Hz, delta connected induction motor takes 120 kW during blocked-rotor test at rated voltage and frequency. If the stator ohmic loss is equal to rotor ohmic loss during blocked rotor test, then the starting torque if DOL starting is used for this motor will bea)822.56 N-m b)954.93 N-mc)525.76 N-m d)730 N-mCorrect answer is option 'B'. Can you explain this answer? theory, EduRev gives you an
ample number of questions to practice A 10-pole, 3-phase, 50 Hz, delta connected induction motor takes 120 kW during blocked-rotor test at rated voltage and frequency. If the stator ohmic loss is equal to rotor ohmic loss during blocked rotor test, then the starting torque if DOL starting is used for this motor will bea)822.56 N-m b)954.93 N-mc)525.76 N-m d)730 N-mCorrect answer is option 'B'. Can you explain this answer? tests, examples and also practice Electrical Engineering (EE) tests.
|
|
Explore Courses for Electrical Engineering (EE) exam
|
|
Signup for Free!
Signup to see your scores go up within 7 days! Learn & Practice with 1000+ FREE Notes, Videos & Tests.
|
© EduRev
|
Education Revolution
|
|
Signup to see your scores
go up within 7 days!
Access 1000+ FREE Docs, Videos and Tests
Takes less than 10 seconds to signup