5. A6-pole, 50-Hz, 8-phase induction motor, running on full-load, develops a useful torque of 162 N-m and it is observed that the rotor electromotive force makes 90 complete cycles per min. Calculate the shaft output. If the mechanical torque lost in friction be 13.5 Nm, find the copper loss in the rotor windings, the input to the motor and the efficiency. Stator losses total 750 W. [16.49 kW; 550 W; 19.2 kW; 86%] 6. The power input to a 500-V, 50-Hz, 6-pole, 3-phase induction motor running at 975 rpm is 40 kW. The stator losses are 1 kW and the friction and windage losses total 2 kW. Calculate (a) the slip (b) the rotor copper loss (c) shaft output (d) the efficiency.[(a) 0.025 (b) 975 W (c) 36.1 kW (d) 90%] pole 3 nhase induction motor develons er of 22 381-W including mechanicallosses which
5. A6-pole, 50-Hz, 8-phase induction motor, running on full-load, develops a useful torque of 162 N-m and it is observed that the rotor electromotive force makes 90 complete cycles per min. Calculate the shaft output. If the mechanical torque lost in friction be 13.5 Nm, find the copper loss in the rotor windings, the input to the motor and the efficiency. Stator losses total 750 W. [16.49 kW; 550 W; 19.2 kW; 86%] 6. The power input to a 500-V, 50-Hz, 6-pole, 3-phase induction motor running at 975 rpm is 40 kW. The stator losses are 1 kW and the friction and windage losses total 2 kW. Calculate (a) the slip (b) the rotor copper loss (c) shaft output (d) the efficiency.[(a) 0.025 (b) 975 W (c) 36.1 kW (d) 90%] pole 3 nhase induction motor develons er of 22 381-W including mechanicallosses which
Introductory Circuit Analysis (13th Edition)
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Author:Robert L. Boylestad
Publisher:Robert L. Boylestad
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![5. A 6-pole, 50-Hz, 8-phase induction motor, running on full-load, develops a useful torque of 162 N-m
and it is observed that the rotor electromotive force makes 90 complete cycles per min. Calculate the
shaft output. If the mechanical torque lost in friction be 13.5 Nm, find the copper loss in the rotor
windings, the input to the motor and the efficiency. Stator losses total 750 W.
[16.49 kW; 550 W; 19.2 kW; 86%]
6. The power input to a 500-V, 50-Hz, 6-pole, 3-phase induction motor running at 975 rpm is 40 kW.
The stator losses are 1 kW and the friction and windage losses total 2 kW. Calculate (a) the slip (b)
the rotor copper loss (c) shaft output (d) the efficiency.[(a) 0.025 (b) 975 W (c) 36.1 kW (d) 90%]
7. A6-pole, 3-phase induction motor develops a power of 22.38kW, including mechanical losses which
total 1.492 kW at a speed of 950 rpm on 550-V, 50-Hz mains. The power factor is 0.88. Calculate
for this load (a) the slip (b) the rotor copper loss (c) the total input if the stator losses are 2000 W
(d) the efficiency (e) the line current (f) the number of complete cycles of the rotor electromotive
force per minute.
8. A 3-phase induction motor has a 4-pole, star-connected stator winding. The motor runs on a 50-Hz
supply with 200 V between lines. The rotor resistance and standstill reactance per phase are 0.1 N
and 0.9 2 respectively. The ratio of rotor to stator turns is 0.67. Calculate (a) total torque at 4% slip
(b) total mechanical power at 4% slip (c) maximum torque (d) speed at maximum torque (e) maximum
mechanical power. Prove the formulae employed, neglecting stator impedance.
[(a) 0.05 (b) 1175 (c) 25.6 kW (d) 82% (e) 30.4 A () 150 ]
[ (a) 40 Nm (b) 6 kW (c) 63.7 Nm (d) 1335 rpm (e) 8.952 kW.]
9. A 3-phase induction motor has a 4-pole, star-connected, stator winding and runs on a 220-V, 50-Hz
supply. The rotor resistance is 0.1 2 and reactance 0.9. The ratio of stator to rotor turns is 1.75.
The full load slip is 5%. Calculate for this load (a) the total torque (b) the shaft output. Find also (c)
the maximum torque (d) the speed at maximum torque.
[ (a) 42 Nm (b) 6.266 kW (c) 56 Nm (d) 1330 rpm ]
10. A 3000-V, 24-pole, 50-Hz 3-phase, star-connected induction motor has a slip-ring rotor of resistance
0.016 2 and standstill reactance 0.265 2 per phase. Full-load torque is obtained at a speed of
247 rpm.
Calculate (a) the ratio of maximum to full-load torque (b) the speed at maximum torque. Neglect
stator impedance.
11. The rotor resistance and standstill reactance of a 3-phase induction motor are respectively 0.015 2
and 0.09 2 per phase. At normal voltage, the full-load slip is 3%. Estimate the percentage reduction
in stator voltage to develop full-load torque at one-half of full-load speed. What is then the power
[(a) 2.61 (b) 235 rpm ]
factor ?
[22.5%; 0.31 ]
12. The power input to a 3-phase, 50-Hz induction motor is 60 kW. The total stator loss is 1000 W. Find
the total mechanical power developed and rotor copper loss if it is observed that the rotor e.m.f.
makes 120 complete cycles per minute.
[56.64 kW; 2.36 kW] (AMIE Sec. B Elect. Machine (E-3) Summer 1990)
13. A balanced three phase induction motor has an efficiency of 0.85 when its output is 44.76 kW. At this
load both the stator copper loss and the rotor copper loss are equal to the core losses. The mechanical
losses are one-fourth of the no-load loss. Calculate the slip.
[4.94%] (AMIE Sec. B Elect. Machines (E-3) Winter 1991)
14. An induction motor is running at 20% slip, the output is 36.775 kW and the total mechanical losses are
1500 W. Estimate Cu losses in the rotor circuit. If the stator losses are 3 kW, estimate efficiency of
the motor.
[9,569 W, 72.35%] (Electrical Engineering-II, Bombay Univ. 1978)
15. A 3- 0, 50-Hz, 500-V, 6-pole induction motor gives an output of 37.3 kW at 955 r.p.m. The power
factor is 0.86, frictional and windage losses total 1.492 kW; stator losses amount to 1.5 kW. Deter-
mine (i) line current (ii) the rotor Cu loss for this load.](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F42279e55-f57e-4b6e-bd34-d8de3e5b8e4b%2F86ea2e5b-d4a2-433a-9623-bab715c90330%2Flydc7d_processed.jpeg&w=3840&q=75)
Transcribed Image Text:5. A 6-pole, 50-Hz, 8-phase induction motor, running on full-load, develops a useful torque of 162 N-m
and it is observed that the rotor electromotive force makes 90 complete cycles per min. Calculate the
shaft output. If the mechanical torque lost in friction be 13.5 Nm, find the copper loss in the rotor
windings, the input to the motor and the efficiency. Stator losses total 750 W.
[16.49 kW; 550 W; 19.2 kW; 86%]
6. The power input to a 500-V, 50-Hz, 6-pole, 3-phase induction motor running at 975 rpm is 40 kW.
The stator losses are 1 kW and the friction and windage losses total 2 kW. Calculate (a) the slip (b)
the rotor copper loss (c) shaft output (d) the efficiency.[(a) 0.025 (b) 975 W (c) 36.1 kW (d) 90%]
7. A6-pole, 3-phase induction motor develops a power of 22.38kW, including mechanical losses which
total 1.492 kW at a speed of 950 rpm on 550-V, 50-Hz mains. The power factor is 0.88. Calculate
for this load (a) the slip (b) the rotor copper loss (c) the total input if the stator losses are 2000 W
(d) the efficiency (e) the line current (f) the number of complete cycles of the rotor electromotive
force per minute.
8. A 3-phase induction motor has a 4-pole, star-connected stator winding. The motor runs on a 50-Hz
supply with 200 V between lines. The rotor resistance and standstill reactance per phase are 0.1 N
and 0.9 2 respectively. The ratio of rotor to stator turns is 0.67. Calculate (a) total torque at 4% slip
(b) total mechanical power at 4% slip (c) maximum torque (d) speed at maximum torque (e) maximum
mechanical power. Prove the formulae employed, neglecting stator impedance.
[(a) 0.05 (b) 1175 (c) 25.6 kW (d) 82% (e) 30.4 A () 150 ]
[ (a) 40 Nm (b) 6 kW (c) 63.7 Nm (d) 1335 rpm (e) 8.952 kW.]
9. A 3-phase induction motor has a 4-pole, star-connected, stator winding and runs on a 220-V, 50-Hz
supply. The rotor resistance is 0.1 2 and reactance 0.9. The ratio of stator to rotor turns is 1.75.
The full load slip is 5%. Calculate for this load (a) the total torque (b) the shaft output. Find also (c)
the maximum torque (d) the speed at maximum torque.
[ (a) 42 Nm (b) 6.266 kW (c) 56 Nm (d) 1330 rpm ]
10. A 3000-V, 24-pole, 50-Hz 3-phase, star-connected induction motor has a slip-ring rotor of resistance
0.016 2 and standstill reactance 0.265 2 per phase. Full-load torque is obtained at a speed of
247 rpm.
Calculate (a) the ratio of maximum to full-load torque (b) the speed at maximum torque. Neglect
stator impedance.
11. The rotor resistance and standstill reactance of a 3-phase induction motor are respectively 0.015 2
and 0.09 2 per phase. At normal voltage, the full-load slip is 3%. Estimate the percentage reduction
in stator voltage to develop full-load torque at one-half of full-load speed. What is then the power
[(a) 2.61 (b) 235 rpm ]
factor ?
[22.5%; 0.31 ]
12. The power input to a 3-phase, 50-Hz induction motor is 60 kW. The total stator loss is 1000 W. Find
the total mechanical power developed and rotor copper loss if it is observed that the rotor e.m.f.
makes 120 complete cycles per minute.
[56.64 kW; 2.36 kW] (AMIE Sec. B Elect. Machine (E-3) Summer 1990)
13. A balanced three phase induction motor has an efficiency of 0.85 when its output is 44.76 kW. At this
load both the stator copper loss and the rotor copper loss are equal to the core losses. The mechanical
losses are one-fourth of the no-load loss. Calculate the slip.
[4.94%] (AMIE Sec. B Elect. Machines (E-3) Winter 1991)
14. An induction motor is running at 20% slip, the output is 36.775 kW and the total mechanical losses are
1500 W. Estimate Cu losses in the rotor circuit. If the stator losses are 3 kW, estimate efficiency of
the motor.
[9,569 W, 72.35%] (Electrical Engineering-II, Bombay Univ. 1978)
15. A 3- 0, 50-Hz, 500-V, 6-pole induction motor gives an output of 37.3 kW at 955 r.p.m. The power
factor is 0.86, frictional and windage losses total 1.492 kW; stator losses amount to 1.5 kW. Deter-
mine (i) line current (ii) the rotor Cu loss for this load.
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