Tutorial Problem No. 19.3 1. Three impedances Z₁, Z, and Z, are mesh-connected to a symmetrical 3-phase, 400-V, 50-Hz supply of phase sequence R→Y→ B. Z₁ = (10 + j0) ohm- between R and Y lines Z₂ = (5 + j6) ohm - between Y and B lines - between B and R lines Z₂ = (5-j5) ohm Calculate the phase and line currents and total power consumed. [40 A, 40 A, 56.6 A ; 95.7 A, 78.4 A, 35.2 A; 44.8 kW] 2. A symmetrical 3-6, 380-V supply feeds a mesh-connected load as follows: Load A: 19 KVA at p.f. 0.5 lag; Load B: 20 kVA at p.f. 0.8 lag: Load C: 10 kVA at p.f. 0.9 load Determine the line currents and their phase angles for RYB sequence. [74.6 Z-51° A, 98.6 Z172.7º A ; 68.3 Z41.8º A] 3. Determine the line currents in an unbalanced Y connected load supplied from a symmetrical 3-0, 440-V, 3-wire system. The branch impedances of the load are: Z₁ = 5 Z 30° ohm, Z,₂ = 10 Z 45° ohm and Z₂ = 10 45° ohm and Z₁ = 10 ≤ 60° ohm. The sequence is RYB. [35.7 A, 32.8 A; 27.7 A] 4. A 3-0, Y-connected alternator supplies an unbalanced load consisting of three impedances (10 + 20), (10-j20) and 102 respectively, connected in star. There is no neutral connection. Calculate the voltage between the star point of the alternator and that of the load. The phase voltage of the alternator is 230 V. [-245.2 V] 5. Non-reactive resistors of 10, 20 and 25 2 are star-connected to the R, Y are B phases of a 400-V, symmetrical system. Determine the current and power in each resistor and the voltage between star point and neutral. Phase sequence, RYB. [16.5 A, 2.72 kW; 13.1 A, 3.43 kW; 11.2 A, 3.14 kW ; 68 V] 6. Determine the line current in an unbalanced, star-connected load supplied from a symmetrical 3- phase, 440-V system. The branch impedance of the load are Z = 5 30° 2, Z, = 10 Z 45° 2 and Z = 1060° 2. The phase sequence is RYB. [35.7 A, 32.8 A, 27.7°A] 7. Three non-reactive resistors of 3, 4 and 5-2 respectively are star-connected to a 3-phase, 400-V symmetrical system, phase sequence RYB. Find (a) the current in each resistor (b) the power dissipated in each resistor (c) the phase angles between the currents and the corresponding line voltages (d) the star-point potential. Draw to scale the complete vector diagram. [(a) 66.5 A, 59.5 A, 51.8 A (b) 13.2, 14.15, 13.4 kW (c) 26°24', 38°10', 25°20 (d) 34 V] 8. An unbalanced Y-connected load is supplied from a 400-V, 3-, 3-wire symmetrical system. The branch circuit impedances and their connection are (2 + j2) Q, R to N; (3-j3) 2, Y to N and (4 + j1) 22, B to N of the load. Calculate (i) the value of the voltage between lines Y and N and (ii) the phase of this voltage relative to the voltage between line R and Y. Phase sequence RYB. [(i) (-216-j 135.2) or 225.5 V (ii) 2° or -178°] 9. A star-connection of resistors R = 10 22; R = 20 22 is made to the terminals A, B and C respectively of a symmetrical 400-V, supply of phase sequence A→B→C. Find the branch voltages and currents and star-point voltage to neutral.
Tutorial Problem No. 19.3 1. Three impedances Z₁, Z, and Z, are mesh-connected to a symmetrical 3-phase, 400-V, 50-Hz supply of phase sequence R→Y→ B. Z₁ = (10 + j0) ohm- between R and Y lines Z₂ = (5 + j6) ohm - between Y and B lines - between B and R lines Z₂ = (5-j5) ohm Calculate the phase and line currents and total power consumed. [40 A, 40 A, 56.6 A ; 95.7 A, 78.4 A, 35.2 A; 44.8 kW] 2. A symmetrical 3-6, 380-V supply feeds a mesh-connected load as follows: Load A: 19 KVA at p.f. 0.5 lag; Load B: 20 kVA at p.f. 0.8 lag: Load C: 10 kVA at p.f. 0.9 load Determine the line currents and their phase angles for RYB sequence. [74.6 Z-51° A, 98.6 Z172.7º A ; 68.3 Z41.8º A] 3. Determine the line currents in an unbalanced Y connected load supplied from a symmetrical 3-0, 440-V, 3-wire system. The branch impedances of the load are: Z₁ = 5 Z 30° ohm, Z,₂ = 10 Z 45° ohm and Z₂ = 10 45° ohm and Z₁ = 10 ≤ 60° ohm. The sequence is RYB. [35.7 A, 32.8 A; 27.7 A] 4. A 3-0, Y-connected alternator supplies an unbalanced load consisting of three impedances (10 + 20), (10-j20) and 102 respectively, connected in star. There is no neutral connection. Calculate the voltage between the star point of the alternator and that of the load. The phase voltage of the alternator is 230 V. [-245.2 V] 5. Non-reactive resistors of 10, 20 and 25 2 are star-connected to the R, Y are B phases of a 400-V, symmetrical system. Determine the current and power in each resistor and the voltage between star point and neutral. Phase sequence, RYB. [16.5 A, 2.72 kW; 13.1 A, 3.43 kW; 11.2 A, 3.14 kW ; 68 V] 6. Determine the line current in an unbalanced, star-connected load supplied from a symmetrical 3- phase, 440-V system. The branch impedance of the load are Z = 5 30° 2, Z, = 10 Z 45° 2 and Z = 1060° 2. The phase sequence is RYB. [35.7 A, 32.8 A, 27.7°A] 7. Three non-reactive resistors of 3, 4 and 5-2 respectively are star-connected to a 3-phase, 400-V symmetrical system, phase sequence RYB. Find (a) the current in each resistor (b) the power dissipated in each resistor (c) the phase angles between the currents and the corresponding line voltages (d) the star-point potential. Draw to scale the complete vector diagram. [(a) 66.5 A, 59.5 A, 51.8 A (b) 13.2, 14.15, 13.4 kW (c) 26°24', 38°10', 25°20 (d) 34 V] 8. An unbalanced Y-connected load is supplied from a 400-V, 3-, 3-wire symmetrical system. The branch circuit impedances and their connection are (2 + j2) Q, R to N; (3-j3) 2, Y to N and (4 + j1) 22, B to N of the load. Calculate (i) the value of the voltage between lines Y and N and (ii) the phase of this voltage relative to the voltage between line R and Y. Phase sequence RYB. [(i) (-216-j 135.2) or 225.5 V (ii) 2° or -178°] 9. A star-connection of resistors R = 10 22; R = 20 22 is made to the terminals A, B and C respectively of a symmetrical 400-V, supply of phase sequence A→B→C. Find the branch voltages and currents and star-point voltage to neutral.
Power System Analysis and Design (MindTap Course List)
6th Edition
ISBN:9781305632134
Author:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma
Publisher:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma
Chapter5: Transmission Lines: Steady-state Operation
Section: Chapter Questions
Problem 5.2MCQ
Related questions
Question
PLS ANS. # 2 ASAP
![Polyphase Circuits
749
small which is equally deterimental to some types of electrical equipment. Since phase voltage
depends on phase sequence, this fact has been made the basis of several types of phase sequence
indicators.* A simple phase sequence indicator may be made by connecting two suitable incandes-
cent lamps and a capacitor in a Y-connection as shown in Fig. 19.102. It will be found that for
phase sequence RYB, lamp L₁ will glow because its phase voltage will be large whereas L₂ will
not glow because of low voltage across it.
When, phase sequence is RBY, opposite conditions develop so that this time L₂ glows but
not L₁.
Another method of determining the phase sequence is by means of a small 3-phase motor.
Once direction of rotation with a known sequence is found, the motor may be used thereafter for
determining an unknown sequence.
Tutorial Problem No. 19.3
1. Three impedances Z₁, Z₂ and Z are mesh-connected to a symmetrical 3-phase, 400-V, 50-Hz
supply of phase sequence R→Y → B.
Z₁ = (10 + j0) ohm- between R and Y lines
Z₁ = (5 + j6) ohm
- between Y and B lines
Z₂ = (5-j5) ohm
- between B and R lines
Calculate the phase and line currents and total power consumed.
[40 A, 40 A, 56.6 A; 95.7 A, 78.4 A, 35.2 A; 44.8 kW]
2. A symmetrical 3-0, 380-V supply feeds a mesh-connected load as follows:
Load A: 19 KVA at p.f. 0.5 lag; Load B: 20 kVA at p.f. 0.8 lag: Load C: 10 kVA at p.f. 0.9 load
Determine the line currents and their phase angles for RYB sequence.
[74.6 -51° A, 98.6
172.7º A ; 68.3 Z41.8º A]
3. Determine the line currents in an unbalanced Y connected load supplied from a symmetrical 3-6,
440-V, 3-wire system. The branch impedances of the load are : Z₁ = 5 ≤ 30° ohm, Z, = 10 Z 45° ohm and
Z₂ = 10 45° ohm and Z₁ = 10 ≤ 60° ohm. The sequence is RYB.
[35.7 A, 32.8 A; 27.7 A]
4. A 3-0, Y-connected alternator supplies an unbalanced load consisting of three impedances (10+
j20), (10 j20) and 1022 respectively, connected in star. There is no neutral connection. Calculate the
voltage between the star point of the alternator and that of the load. The phase voltage of the alternator is 230
V.
[-245.2 V]
5. Non-reactive resistors of 10, 20 and 25 are star-connected to the R, Y are B phases of a 400-V,
symmetrical system. Determine the current and power in each resistor and the voltage between star point and
neutral. Phase sequence, RYB.
[16.5 A, 2.72 kW; 13.1 A, 3.43 kW; 11.2 A, 3.14 kW ; 68 V]
6. Determine the line current in an unbalanced, star-connected load supplied from a symmetrical 3-
phase, 440-V system. The branch impedance of the load are Z₁ = 5 < 30⁰°, Zy = 10 Z 45° 22 and Z =
1060° 2. The phase sequence is RYB.
[35.7 A, 32.8 A, 27.7 A]
7. Three non-reactive resistors of 3, 4 and 5-2 respectively are star-connected to a 3-phase, 400-V
symmetrical system, phase sequence RYB. Find (a) the current in each resistor (b) the power dissipated in
each resistor (c) the phase angles between the currents and the corresponding line voltages (d) the star-point
potential. Draw to scale the complete vector diagram.
[(a) 66.5 A, 59.5 A, 51.8 A (b) 13.2, 14.15, 13.4 kW (c) 26°24', 38°10', 25°20 (d) 34 V]
8. An unbalanced Y-connected load is supplied from a 400-V, 3-0, 3-wire symmetrical system. The
branch circuit impedances and their connection are (2 + j2) Q, R to N; (3-j3) Q, Y to N and (4+j1) Q,
B to N of the load. Calculate (i) the value of the voltage between lines Y and N and (ii) the phase of this
voltage relative to the voltage between line R and Y. Phase sequence RYB.
[(i) (-216-j 135.2) or 225.5 V (ii) 2º or -178°]
9. A star-connection of resistors R = 10 2 R₁ = 20 22 is made to the terminals A, B and C
respectively of a symmetrical 400-V, supply of phase sequence A→B→ C. Find the branch voltages and
currents and star-point voltage to neutral.
* It may, however, be noted that phase sequence of currents in an unbalanced load is not necessarily the
same as the voltage phase sequence. Unless indicated otherwise, voltage phase sequence is implied.
Copyrighted material](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Fc429c5e8-0790-4e71-b3e1-d726dda280b4%2F2385a66d-072e-4b71-ad7b-bf8ca8c233ce%2F27ze07c_processed.png&w=3840&q=75)
Transcribed Image Text:Polyphase Circuits
749
small which is equally deterimental to some types of electrical equipment. Since phase voltage
depends on phase sequence, this fact has been made the basis of several types of phase sequence
indicators.* A simple phase sequence indicator may be made by connecting two suitable incandes-
cent lamps and a capacitor in a Y-connection as shown in Fig. 19.102. It will be found that for
phase sequence RYB, lamp L₁ will glow because its phase voltage will be large whereas L₂ will
not glow because of low voltage across it.
When, phase sequence is RBY, opposite conditions develop so that this time L₂ glows but
not L₁.
Another method of determining the phase sequence is by means of a small 3-phase motor.
Once direction of rotation with a known sequence is found, the motor may be used thereafter for
determining an unknown sequence.
Tutorial Problem No. 19.3
1. Three impedances Z₁, Z₂ and Z are mesh-connected to a symmetrical 3-phase, 400-V, 50-Hz
supply of phase sequence R→Y → B.
Z₁ = (10 + j0) ohm- between R and Y lines
Z₁ = (5 + j6) ohm
- between Y and B lines
Z₂ = (5-j5) ohm
- between B and R lines
Calculate the phase and line currents and total power consumed.
[40 A, 40 A, 56.6 A; 95.7 A, 78.4 A, 35.2 A; 44.8 kW]
2. A symmetrical 3-0, 380-V supply feeds a mesh-connected load as follows:
Load A: 19 KVA at p.f. 0.5 lag; Load B: 20 kVA at p.f. 0.8 lag: Load C: 10 kVA at p.f. 0.9 load
Determine the line currents and their phase angles for RYB sequence.
[74.6 -51° A, 98.6
172.7º A ; 68.3 Z41.8º A]
3. Determine the line currents in an unbalanced Y connected load supplied from a symmetrical 3-6,
440-V, 3-wire system. The branch impedances of the load are : Z₁ = 5 ≤ 30° ohm, Z, = 10 Z 45° ohm and
Z₂ = 10 45° ohm and Z₁ = 10 ≤ 60° ohm. The sequence is RYB.
[35.7 A, 32.8 A; 27.7 A]
4. A 3-0, Y-connected alternator supplies an unbalanced load consisting of three impedances (10+
j20), (10 j20) and 1022 respectively, connected in star. There is no neutral connection. Calculate the
voltage between the star point of the alternator and that of the load. The phase voltage of the alternator is 230
V.
[-245.2 V]
5. Non-reactive resistors of 10, 20 and 25 are star-connected to the R, Y are B phases of a 400-V,
symmetrical system. Determine the current and power in each resistor and the voltage between star point and
neutral. Phase sequence, RYB.
[16.5 A, 2.72 kW; 13.1 A, 3.43 kW; 11.2 A, 3.14 kW ; 68 V]
6. Determine the line current in an unbalanced, star-connected load supplied from a symmetrical 3-
phase, 440-V system. The branch impedance of the load are Z₁ = 5 < 30⁰°, Zy = 10 Z 45° 22 and Z =
1060° 2. The phase sequence is RYB.
[35.7 A, 32.8 A, 27.7 A]
7. Three non-reactive resistors of 3, 4 and 5-2 respectively are star-connected to a 3-phase, 400-V
symmetrical system, phase sequence RYB. Find (a) the current in each resistor (b) the power dissipated in
each resistor (c) the phase angles between the currents and the corresponding line voltages (d) the star-point
potential. Draw to scale the complete vector diagram.
[(a) 66.5 A, 59.5 A, 51.8 A (b) 13.2, 14.15, 13.4 kW (c) 26°24', 38°10', 25°20 (d) 34 V]
8. An unbalanced Y-connected load is supplied from a 400-V, 3-0, 3-wire symmetrical system. The
branch circuit impedances and their connection are (2 + j2) Q, R to N; (3-j3) Q, Y to N and (4+j1) Q,
B to N of the load. Calculate (i) the value of the voltage between lines Y and N and (ii) the phase of this
voltage relative to the voltage between line R and Y. Phase sequence RYB.
[(i) (-216-j 135.2) or 225.5 V (ii) 2º or -178°]
9. A star-connection of resistors R = 10 2 R₁ = 20 22 is made to the terminals A, B and C
respectively of a symmetrical 400-V, supply of phase sequence A→B→ C. Find the branch voltages and
currents and star-point voltage to neutral.
* It may, however, be noted that phase sequence of currents in an unbalanced load is not necessarily the
same as the voltage phase sequence. Unless indicated otherwise, voltage phase sequence is implied.
Copyrighted material
Expert Solution
This question has been solved!
Explore an expertly crafted, step-by-step solution for a thorough understanding of key concepts.
Step by step
Solved in 2 steps
Knowledge Booster
Learn more about
Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, electrical-engineering and related others by exploring similar questions and additional content below.Recommended textbooks for you
Power System Analysis and Design (MindTap Course …
Electrical Engineering
ISBN:
9781305632134
Author:
J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma
Publisher:
Cengage Learning
Power System Analysis and Design (MindTap Course …
Electrical Engineering
ISBN:
9781305632134
Author:
J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma
Publisher:
Cengage Learning