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1. A 440 volts d.c. shunt motor has an armature resistance of 0.5 2 and field resistance of 180 . Determine back e.m.f when.giving an E output of 7.46 kW at 85% efficiency. (Ans.: 431.25 V) 240 V dc shunt motor has an armature resistance of 0 20 The rated full load current is

1. A 440 volts d.c. shunt motor has an armature resistance of 0.5 2 and field resistance of 180 . Determine back e.m.f when.giving an E output of 7.46 kW at 85% efficiency. (Ans.: 431.25 V) 240 V dc shunt motor has an armature resistance of 0 20 The rated full load current is

Introductory Circuit Analysis (13th Edition)
Introductory Circuit Analysis (13th Edition)
13th Edition
ISBN:9780133923605
Author:Robert L. Boylestad
Publisher:Robert L. Boylestad
Chapter1: Introduction
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1. A 440 volts d.c. shunt motor has an armature resistance of 0.5 and field resistance of 18 . Determine back e.m.f when giving an E output of 7.46 kW at 85% efficiency. (Ans.: 431.25 V) 2. A 240 V d.c. shunt motor has an armature resistance of 0.2 2. The rated full load current is 80 A. Calculate the current at the instant of starting if the motor is started direct on line and express it in terms of the full load current. Calculate the value of starting resistance to limit the starting current to 150% of rated current. 3. A d.c. shunt machine has rating of 10 kW, 500 V. The armature resistance is 0.1 2 Calculate the induced e.m.f. if machine is made to run as i) Generator ii) Motor. (Ans. : 502.5 V, 499.85 V) 4. A d.c. shunt motor connected to a 230 V supply takes a line current of 12 A, at some load. If = 10 and R = 230 2, calculate the back e.m.f. (Ans. : 1200 A, 0.133 2) (Ans. : 219 V) R. 5. A 4 pole, 250 V, series motor has a wave connected armature with 1254 conductors. The flux per pole is 22 mWb when motor is taking 50 A. Armature and field resistance are 0.2 and 0.2 N respectively. Calculate its speed. 6. Determine the total torque developed in a 250 V, 4 pole d.c. shunt motor with lap winding, accomodated in 60 slots, each containing 20 conductors. The armature current is 50 A and the flux per pole is 23 mWb. 7. A 250 V, d.c. shunt motor takes 6 A line current on no load and runs at 1000 r.p.m. The field resistance is 250 2 and armature resistance is 0.2 2 If the full load line current is 26 A, calculate the full load speed assuming constant flux. 8. A 4 pole, d.c. shunt motor takes 22.5 A from a 250 V supply. R, The armature is wave wound with 300 conductors. If the flux per pole is 0.02 Wb, calculate i) Speed li) Torque developed iii) Gross power developed. (Ans. : 250.1 r.p.m.) (Ans. : 219.5 N-m) (Ans. : 984 r.p.m.) = 0.5 N and Rh = 125 N. (Ans. : 1199 r.p.m, 39.1 N-m, 4.915 kW) 9. A 250 V d.c. shunt motor has no load speed 1200 r.p.m. The line current being 5 A. When fully loaded line current is 30 A. Shunt field resistance is 250 ohms and armature resistance is 0.5 ohms. Find the speed of the motor on full load and its speed regulation. (Ans. : 1139.51 r.p.m., 5.3 %) 10. A 4 pole, 250 V d.c. series motor has a wave connected armature with 496 conductors. Calculate i) Gross torque ii) Shaft torque iii) Efficiency iv) Armature resistance. Assume flux per pole 22 mWb, the armature current of 50A, the speed N = 462 r.p.m., Re = 0.14 N and (Ans. : i) 173.66 N-m ii) 161.621 N-m iii) 86.92 % iv) 0.1896 Q) %3D mechanical losses are 810 W. 11. A 460 V, d.c. series motor runs at 500 r.p.m. taking a current of 40 A. calculate the speed if motor takes a current of 30 A. Total resistance of the motor across the terminals is 0.8 2. Assume flux proportional to field current. (Ans. : 679.127 r.p.m.)
Transcribed Image Text:1. A 440 volts d.c. shunt motor has an armature resistance of 0.5 and field resistance of 18 . Determine back e.m.f when giving an E output of 7.46 kW at 85% efficiency. (Ans.: 431.25 V) 2. A 240 V d.c. shunt motor has an armature resistance of 0.2 2. The rated full load current is 80 A. Calculate the current at the instant of starting if the motor is started direct on line and express it in terms of the full load current. Calculate the value of starting resistance to limit the starting current to 150% of rated current. 3. A d.c. shunt machine has rating of 10 kW, 500 V. The armature resistance is 0.1 2 Calculate the induced e.m.f. if machine is made to run as i) Generator ii) Motor. (Ans. : 502.5 V, 499.85 V) 4. A d.c. shunt motor connected to a 230 V supply takes a line current of 12 A, at some load. If = 10 and R = 230 2, calculate the back e.m.f. (Ans. : 1200 A, 0.133 2) (Ans. : 219 V) R. 5. A 4 pole, 250 V, series motor has a wave connected armature with 1254 conductors. The flux per pole is 22 mWb when motor is taking 50 A. Armature and field resistance are 0.2 and 0.2 N respectively. Calculate its speed. 6. Determine the total torque developed in a 250 V, 4 pole d.c. shunt motor with lap winding, accomodated in 60 slots, each containing 20 conductors. The armature current is 50 A and the flux per pole is 23 mWb. 7. A 250 V, d.c. shunt motor takes 6 A line current on no load and runs at 1000 r.p.m. The field resistance is 250 2 and armature resistance is 0.2 2 If the full load line current is 26 A, calculate the full load speed assuming constant flux. 8. A 4 pole, d.c. shunt motor takes 22.5 A from a 250 V supply. R, The armature is wave wound with 300 conductors. If the flux per pole is 0.02 Wb, calculate i) Speed li) Torque developed iii) Gross power developed. (Ans. : 250.1 r.p.m.) (Ans. : 219.5 N-m) (Ans. : 984 r.p.m.) = 0.5 N and Rh = 125 N. (Ans. : 1199 r.p.m, 39.1 N-m, 4.915 kW) 9. A 250 V d.c. shunt motor has no load speed 1200 r.p.m. The line current being 5 A. When fully loaded line current is 30 A. Shunt field resistance is 250 ohms and armature resistance is 0.5 ohms. Find the speed of the motor on full load and its speed regulation. (Ans. : 1139.51 r.p.m., 5.3 %) 10. A 4 pole, 250 V d.c. series motor has a wave connected armature with 496 conductors. Calculate i) Gross torque ii) Shaft torque iii) Efficiency iv) Armature resistance. Assume flux per pole 22 mWb, the armature current of 50A, the speed N = 462 r.p.m., Re = 0.14 N and (Ans. : i) 173.66 N-m ii) 161.621 N-m iii) 86.92 % iv) 0.1896 Q) %3D mechanical losses are 810 W. 11. A 460 V, d.c. series motor runs at 500 r.p.m. taking a current of 40 A. calculate the speed if motor takes a current of 30 A. Total resistance of the motor across the terminals is 0.8 2. Assume flux proportional to field current. (Ans. : 679.127 r.p.m.)
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