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A 3-phase squirrel cage induction motor has maximum torque equal to twice the full-load torque. The per phase rotor resistance and per phase standstill reactance referred to stator are 0.2 Ω and 2 Ω respectively (Stator impedance is neglected). What is the ratio of motor starting toque to its full-load torque, if the motor is started by direct-on-line starter?
- a)0.396
- b)0.194
- c)0.198
- d)0.400
Correct answer is option 'A'. Can you explain this answer?
Verified Answer
A 3-phase squirrel cage induction motor has maximum torque equal to tw...
From equations (i) and (ii), we have
Most Upvoted Answer
A 3-phase squirrel cage induction motor has maximum torque equal to tw...
Ohms and 0.5 ohms, respectively. The motor is connected to a 400V, 50Hz, 4-pole supply. Find the following:
1. Full-load torque
2. Maximum torque
3. Slip at full-load torque
4. Slip at maximum torque
5. Starting current if the motor is started with a delta connection
6. Starting current if the motor is started with a star-delta connection
Solution:
1. Full-load torque:
The full-load torque is given by:
Tfl = (3 x V^2 x cosφ) / (2 x π x f x (R2^2 + X2^2))
where:
V = 400V (line voltage)
φ = power factor (assumed to be 0.85)
f = 50Hz
R2 = 0.2 ohms (per phase rotor resistance)
X2 = 0.5 ohms (per phase standstill reactance)
Substituting the values, we get:
Tfl = (3 x 400^2 x 0.85) / (2 x π x 50 x (0.2^2 + 0.5^2))
Tfl = 45.9 Nm
Therefore, the full-load torque is 45.9 Nm.
2. Maximum torque:
The maximum torque is given by:
Tmax = (3 x V^2) / (2 x π x f x R2)
Substituting the values, we get:
Tmax = (3 x 400^2) / (2 x π x 50 x 0.2)
Tmax = 574.5 Nm
Therefore, the maximum torque is 574.5 Nm.
3. Slip at full-load torque:
The slip at full-load torque can be calculated using the formula:
sfl = (Tfl / Tmax)^(1/2)
Substituting the values, we get:
sfl = (45.9 / 574.5)^(1/2)
sfl = 0.335 or 33.5%
Therefore, the slip at full-load torque is 33.5%.
4. Slip at maximum torque:
The slip at maximum torque is 0.5, as the maximum torque occurs at the point where the slip is equal to the rotor resistance divided by the sum of rotor resistance and reactance.
5. Starting current if the motor is started with a delta connection:
The starting current for a delta connection is given by:
Istart = (V / (√3 x Zstart)) x K
where:
Zstart = (R2 + jX2) / s
K = 1 for a delta connection
At standstill, s = 1, so we get:
Zstart = (0.2 + j0.5) / 1
Zstart = 0.2 + j0.5
Substituting the values, we get:
Istart = (400 / (√3 x (0.2 + j0.5))) x 1
Istart = 911.5 A (approximately)
Therefore, the starting current if the motor is started with a delta connection is 911.5 A (approximately).
6. Starting current if the motor is started with a star-delta connection:
The starting current for a star-d
1. Full-load torque
2. Maximum torque
3. Slip at full-load torque
4. Slip at maximum torque
5. Starting current if the motor is started with a delta connection
6. Starting current if the motor is started with a star-delta connection
Solution:
1. Full-load torque:
The full-load torque is given by:
Tfl = (3 x V^2 x cosφ) / (2 x π x f x (R2^2 + X2^2))
where:
V = 400V (line voltage)
φ = power factor (assumed to be 0.85)
f = 50Hz
R2 = 0.2 ohms (per phase rotor resistance)
X2 = 0.5 ohms (per phase standstill reactance)
Substituting the values, we get:
Tfl = (3 x 400^2 x 0.85) / (2 x π x 50 x (0.2^2 + 0.5^2))
Tfl = 45.9 Nm
Therefore, the full-load torque is 45.9 Nm.
2. Maximum torque:
The maximum torque is given by:
Tmax = (3 x V^2) / (2 x π x f x R2)
Substituting the values, we get:
Tmax = (3 x 400^2) / (2 x π x 50 x 0.2)
Tmax = 574.5 Nm
Therefore, the maximum torque is 574.5 Nm.
3. Slip at full-load torque:
The slip at full-load torque can be calculated using the formula:
sfl = (Tfl / Tmax)^(1/2)
Substituting the values, we get:
sfl = (45.9 / 574.5)^(1/2)
sfl = 0.335 or 33.5%
Therefore, the slip at full-load torque is 33.5%.
4. Slip at maximum torque:
The slip at maximum torque is 0.5, as the maximum torque occurs at the point where the slip is equal to the rotor resistance divided by the sum of rotor resistance and reactance.
5. Starting current if the motor is started with a delta connection:
The starting current for a delta connection is given by:
Istart = (V / (√3 x Zstart)) x K
where:
Zstart = (R2 + jX2) / s
K = 1 for a delta connection
At standstill, s = 1, so we get:
Zstart = (0.2 + j0.5) / 1
Zstart = 0.2 + j0.5
Substituting the values, we get:
Istart = (400 / (√3 x (0.2 + j0.5))) x 1
Istart = 911.5 A (approximately)
Therefore, the starting current if the motor is started with a delta connection is 911.5 A (approximately).
6. Starting current if the motor is started with a star-delta connection:
The starting current for a star-d
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A 3-phase squirrel cage induction motor has maximum torque equal to tw...
Derive the condition for maximum torque under running condition of a 3 phase
induction motor.
induction motor.
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A 3-phase squirrel cage induction motor has maximum torque equal to twice the full-load torque. The per phase rotor resistance and per phase standstill reactance referred to stator are 0.2 Ω and 2 Ω respectively (Stator impedance is neglected). What is the ratio of motor starting toque to its full-load torque, if the motor is started by direct-on-line starter?a)0.396 b)0.194c)0.198 d)0.400Correct answer is option 'A'. 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 3-phase squirrel cage induction motor has maximum torque equal to twice the full-load torque. The per phase rotor resistance and per phase standstill reactance referred to stator are 0.2 Ω and 2 Ω respectively (Stator impedance is neglected). What is the ratio of motor starting toque to its full-load torque, if the motor is started by direct-on-line starter?a)0.396 b)0.194c)0.198 d)0.400Correct answer is option 'A'. 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 3-phase squirrel cage induction motor has maximum torque equal to twice the full-load torque. The per phase rotor resistance and per phase standstill reactance referred to stator are 0.2 Ω and 2 Ω respectively (Stator impedance is neglected). What is the ratio of motor starting toque to its full-load torque, if the motor is started by direct-on-line starter?a)0.396 b)0.194c)0.198 d)0.400Correct answer is option 'A'. Can you explain this answer?.
A 3-phase squirrel cage induction motor has maximum torque equal to twice the full-load torque. The per phase rotor resistance and per phase standstill reactance referred to stator are 0.2 Ω and 2 Ω respectively (Stator impedance is neglected). What is the ratio of motor starting toque to its full-load torque, if the motor is started by direct-on-line starter?a)0.396 b)0.194c)0.198 d)0.400Correct answer is option 'A'. 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 3-phase squirrel cage induction motor has maximum torque equal to twice the full-load torque. The per phase rotor resistance and per phase standstill reactance referred to stator are 0.2 Ω and 2 Ω respectively (Stator impedance is neglected). What is the ratio of motor starting toque to its full-load torque, if the motor is started by direct-on-line starter?a)0.396 b)0.194c)0.198 d)0.400Correct answer is option 'A'. 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 3-phase squirrel cage induction motor has maximum torque equal to twice the full-load torque. The per phase rotor resistance and per phase standstill reactance referred to stator are 0.2 Ω and 2 Ω respectively (Stator impedance is neglected). What is the ratio of motor starting toque to its full-load torque, if the motor is started by direct-on-line starter?a)0.396 b)0.194c)0.198 d)0.400Correct answer is option 'A'. Can you explain this answer?.
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A 3-phase squirrel cage induction motor has maximum torque equal to twice the full-load torque. The per phase rotor resistance and per phase standstill reactance referred to stator are 0.2 Ω and 2 Ω respectively (Stator impedance is neglected). What is the ratio of motor starting toque to its full-load torque, if the motor is started by direct-on-line starter?a)0.396 b)0.194c)0.198 d)0.400Correct answer is option 'A'. Can you explain this answer?, a detailed solution for A 3-phase squirrel cage induction motor has maximum torque equal to twice the full-load torque. The per phase rotor resistance and per phase standstill reactance referred to stator are 0.2 Ω and 2 Ω respectively (Stator impedance is neglected). What is the ratio of motor starting toque to its full-load torque, if the motor is started by direct-on-line starter?a)0.396 b)0.194c)0.198 d)0.400Correct answer is option 'A'. Can you explain this answer? has been provided alongside types of A 3-phase squirrel cage induction motor has maximum torque equal to twice the full-load torque. The per phase rotor resistance and per phase standstill reactance referred to stator are 0.2 Ω and 2 Ω respectively (Stator impedance is neglected). What is the ratio of motor starting toque to its full-load torque, if the motor is started by direct-on-line starter?a)0.396 b)0.194c)0.198 d)0.400Correct answer is option 'A'. Can you explain this answer? theory, EduRev gives you an
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