11:06 PM р " A K/S DOC-20240917-WA0008. Phoenix Files 1128 Electrical Technology Tutorial Problems 32.1 × 1. The number of turns on the primary and secondary windings of a 1-o transformer are 350 and 35 respectively. If the primary is connected to a 2.2 kV, 50-Hz supply, determine the secondary voltage on no-load. [220 V] (Elect. Engg.-II, Kerala Univ. 1980) 2. A 3000/200-V, 50-Hz, 1-phase transformer is built on a core having an effective cross-sectional area of 150 cm² and has 80 turns in the low-voltage winding. Calculate (a) the value of the maximum flux density in the core (b) the number of turns in the high-voltage winding. [(a) 0.75 Wb/m² (b) 1200] 3. A 3,300/230-V, 50-Hz, 1-phase transformer is to be worked at a maximum flux density of 1.2 Wb/m² in the core. The effective cross-sectional area of the transformer core is 150 cm². Calculate suitable values of primary and secondary turns. [830; 58] 4. A 40-kVA, 3,300/240-V, 50 Hz, 1-phase transformer has 660 turns on the primary. Determine (a) the number of turns on the secondary (b) the maximum value of flux in the core (c) the approximate value of primary and secondary full-load currents. Internal drops in the windings are to be ignored. [(a) 48 (b) 22.5 mWb (c) 12.1 A; 166.7 A] 5. A double-wound, 1-phase transformer is required to step down from 1900 V to 240 V, 50-Hz. It is to have 1.5 V per turn. Calculate the required number of turns on the primary and secondary windings respectively. The peak value of flux density is required to be not more than 1.2 Wb/m². Calculate the required cross-sectional area of the steel core. If the output is 10 kVA, calculate the secondary current. [1,267; 160; 56.4 cm²; 41.75 A] 6. The no-load voltage ratio in a 1-phase, 50-Hz, core-type transformer is 1,200/440. Find the number of turns in each winding if the maximum flux is to be 0.075 Wb. [24 and 74 turns] 7. A 1-phase transformer has 500 primary and 1200 secondary turns. The net cross-sectional area of the core is 75 cm². If the primary winding be connected to a 400-V, 50 Hz supply, calculate. (i) the peak value of flux density in the core and (ii) voltage induced in the secondary winding. [0.48 Wh/m²; 60 V] 8. A 10-kVA, 1-phase transformer has a turn ratio of 300/23. The primary is connected to a 1500-V, 60 Hz supply. Find the secondary volts on open-circuit and the approximate values of the currents in the two windings on full-load. Find also the maximum value of the flux. [115 V; 6.67 A; 87 A; 11.75 mWb] 9. A 100-kVA, 3300/400-V, 50 Hz, 1 phase transformer has 110 turns on the secondary. Calculate the approximate values of the primary and secondary full-load currents, the maximum value of flux in the core and the number of primary turns. How does the core flux vary with load? [30.3 A; 250 A; 16.4 mWb; 907] 10. The no-load current of a transformer is 5.0 A at 0.3 power factor when supplied at 230-V, 50-Hz. The number of turns on the primary winding is 200. Calculate (i) the maximum value of flux in the core (ii) the core loss (iii) the magnetising current. [5.18 mWb; 345 W; 4.77 A] 11. The no-load current of a transformer is 15 at a power factor of 0.2 when connected to a 460-V, 50-Hz supply. If the primary winding has 550 turns, calculate (a) the magnetising component of no-load current (b) the iron loss (c) the maximum value of the flux in the core. [(a) 14.7 A (b) 1,380 W (c) 3.77 mWb] 12. The no-load current of a transformer is 4.0 A at 0.25 p.f. when supplied at 250-V, 50 Hz. The number of turns on the primary winding is 200. Calculate (i) the r.m.s. value of the flux in the core (assume sinusoidal flux) (ii) the core loss (iii) the magnetising current. [(i) 3.96 mWb (ii) 250 W (iii) 3.87 A] Catalogue = Play Q Search n Share

11:06 PM р " A K/S DOC-20240917-WA0008. Phoenix Files 1128 Electrical Technology Tutorial Problems 32.1 × 1. The number of turns on the primary and secondary windings of a 1-o transformer are 350 and 35 respectively. If the primary is connected to a 2.2 kV, 50-Hz supply, determine the secondary voltage on no-load. [220 V] (Elect. Engg.-II, Kerala Univ. 1980) 2. A 3000/200-V, 50-Hz, 1-phase transformer is built on a core having an effective cross-sectional area of 150 cm² and has 80 turns in the low-voltage winding. Calculate (a) the value of the maximum flux density in the core (b) the number of turns in the high-voltage winding. [(a) 0.75 Wb/m² (b) 1200] 3. A 3,300/230-V, 50-Hz, 1-phase transformer is to be worked at a maximum flux density of 1.2 Wb/m² in the core. The effective cross-sectional area of the transformer core is 150 cm². Calculate suitable values of primary and secondary turns. [830; 58] 4. A 40-kVA, 3,300/240-V, 50 Hz, 1-phase transformer has 660 turns on the primary. Determine (a) the number of turns on the secondary (b) the maximum value of flux in the core (c) the approximate value of primary and secondary full-load currents. Internal drops in the windings are to be ignored. [(a) 48 (b) 22.5 mWb (c) 12.1 A; 166.7 A] 5. A double-wound, 1-phase transformer is required to step down from 1900 V to 240 V, 50-Hz. It is to have 1.5 V per turn. Calculate the required number of turns on the primary and secondary windings respectively. The peak value of flux density is required to be not more than 1.2 Wb/m². Calculate the required cross-sectional area of the steel core. If the output is 10 kVA, calculate the secondary current. [1,267; 160; 56.4 cm²; 41.75 A] 6. The no-load voltage ratio in a 1-phase, 50-Hz, core-type transformer is 1,200/440. Find the number of turns in each winding if the maximum flux is to be 0.075 Wb. [24 and 74 turns] 7. A 1-phase transformer has 500 primary and 1200 secondary turns. The net cross-sectional area of the core is 75 cm². If the primary winding be connected to a 400-V, 50 Hz supply, calculate. (i) the peak value of flux density in the core and (ii) voltage induced in the secondary winding. [0.48 Wh/m²; 60 V] 8. A 10-kVA, 1-phase transformer has a turn ratio of 300/23. The primary is connected to a 1500-V, 60 Hz supply. Find the secondary volts on open-circuit and the approximate values of the currents in the two windings on full-load. Find also the maximum value of the flux. [115 V; 6.67 A; 87 A; 11.75 mWb] 9. A 100-kVA, 3300/400-V, 50 Hz, 1 phase transformer has 110 turns on the secondary. Calculate the approximate values of the primary and secondary full-load currents, the maximum value of flux in the core and the number of primary turns. How does the core flux vary with load? [30.3 A; 250 A; 16.4 mWb; 907] 10. The no-load current of a transformer is 5.0 A at 0.3 power factor when supplied at 230-V, 50-Hz. The number of turns on the primary winding is 200. Calculate (i) the maximum value of flux in the core (ii) the core loss (iii) the magnetising current. [5.18 mWb; 345 W; 4.77 A] 11. The no-load current of a transformer is 15 at a power factor of 0.2 when connected to a 460-V, 50-Hz supply. If the primary winding has 550 turns, calculate (a) the magnetising component of no-load current (b) the iron loss (c) the maximum value of the flux in the core. [(a) 14.7 A (b) 1,380 W (c) 3.77 mWb] 12. The no-load current of a transformer is 4.0 A at 0.25 p.f. when supplied at 250-V, 50 Hz. The number of turns on the primary winding is 200. Calculate (i) the r.m.s. value of the flux in the core (assume sinusoidal flux) (ii) the core loss (iii) the magnetising current. [(i) 3.96 mWb (ii) 250 W (iii) 3.87 A] Catalogue = Play Q Search n Share

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

Chapter3: Power Transformers

Section: Chapter Questions

Problem 3.16P: A single-phase, 50-kVA,2400/240-V,60-Hz distribution transformer has the following parameters:...

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