Q1-A 3-phase step down transformer 1200 KVA , 11000/2200 V, 50 Hz .The resistance /phase and leakage reactance/phase of the primary winding are 1.2Q and 4.8Q and the corresponding values for the secondary winding are 0.01Q and 0.06Q respectively if the primary winding is connected in delta and secondary in star. calculate: 1)The voltage to be applied at normal frequency to the primary to circulate full-load current through it when the secondary is short-circuited ii) The full load copper loss Q2- A 3-phase 250KVA, 11000/416 transformer is delta-connected on the primary and star connected on the secondary. The primary resistance / phase is 8 Q and secondary resistance/phase is 0.0034 Q. determine the efficiency on full-load at 0.8 power factor lagging if the iron loss is 660 W Q1-A 3-phase step down transformer 1200 KVA , 11000/2200 V, 50 Hz .The resistance/phase and leakage reactance/phase of the primary winding are 1.22 and 4.82 and thecorresponding values for the secondary winding are 0.012 and 0.062 respectively if theprimary winding is connected in delta and secondary in star. calculate:i)The voltage to be applied at normal frequency to the primary to circulate full-loadcurrent through it when the secondary is short-circuitedii) The full load copper lossQ2- A 3-phase 250KVA, 11000/416 transformer is delta-connected on the primary andstar connected on the secondary. The primary resistance / phase is 8 2 and secondaryresistance/phase is 0.0034 2. determine the efficiency on full-load at o.8 power factorlagging if the iron loss is 660 W03

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Q1-A 3-phase step down transformer 1200 KVA , 11000/2200 V, 50 Hz .The resistance /phase and leakage reactance/phase of the primary winding are 1.22 and 4.82 and the corresponding values for the secondary winding are 0.012 and 0.06N respectively if the primary winding is connected in delta and secondary in star. calculate: i)The voltage to be applied at normal frequency to the primary to circulate full-load current through it when the secondary is short-circuited ii) The full load copper loss

Q1-A 3-phase step down transformer 1200 KVA , 11000/2200 V, 50 Hz .The resistance /phase and leakage reactance/phase of the primary winding are 1.22 and 4.82 and the corresponding values for the secondary winding are 0.012 and 0.06N respectively if the primary winding is connected in delta and secondary in star. calculate: i)The voltage to be applied at normal frequency to the primary to circulate full-load current through it when the secondary is short-circuited ii) The full load copper loss

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 3.4P: A single-phase 100-kVA,2400/240-volt,60-Hz distribution transformer is used as a step-down...

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Consider Figure 3.4. For an ideal phase-shifting transformer, the imda nce is unchanged when it is referred from one side to the other. (a) True (b) False
A single-phase, 50-kVA,2400/240-V,60-Hz distribution transformer has the following parameters: Resistance of the 2400-V winding: R1=0.75 Resistance of the 240-V winding: R2=0.0075 Leakage reactance of the 2400-V winding: X1=1.0 Leakage reactance of the 240-V winding: X2=0.01 Exciting admittance on the 240-V side =0.003j0.02S (a) Draw the equivalent circuit referred to the high-voltage side of the transformer. (b) Draw the equivalent circuit referred to the low-voltage side of the transformer. Show the numerical values of impedances on the equivalent circuits.
The ratings of a three-phase three-winding transformer are Primary(1): Y connected 66kV,15MVA Secondary (2): Y connected, 13.2kV,10MVA Tertiary (3): A connected, 2.3kV,5MVA Neglecting winding resistances and exciting current, the per-unit leakage reactances are X12=0.08 on a 15-MVA,66-kV base X13=0.10 on a 15-MVA,66-kV base X23=0.09 on a 10-MVA,13.2-kV base (a) Determine the per-unit reactances X1,X2,X3 of the equivalent circuit on a 15-MVA,66-kV base at the primary terminals. (b) Purely resistive loads of 7.5 MW at 13.2 kV and 5 MW at 2.3kV are connected to the secondary and tertiary sides of the transformer, respectively. Draw the per- unit impedance diagram, showing the per-unit impedances on a 15-MVA,66-kV base at the primary terminals.
Three single-phase, two-winding transformers, each rated 450MVA,20kV/288.7kV, with leakage reactance Xeq=0.10perunit, are connected to form a three-phase bank. The high-voltage windings are connected in Y with a solidly grounded neutral. Draw the per-unit equivalent circuit if the low-voltage windings are connected (a) in with American standard phase shift or (b) in Y with an open neutral. Use the transformer ratings as base quantities. Winding resistances and exciting current are neglected.
A single-phase two-winding transformer rated 90MVA,80/120kV is to be connected as an autotransformer rated 80/200kV. Assume that the transformer is ideal. (a) Draw a schematic diagram of the ideal transformer connected as an autotransformer. showing the voltages, currents, and dot notation for polarity. (b) Determine the permissible kVA rating of the autotransformer if the winding currents and voltages are not to exceed the rated values as a two-winding transformer. How much of the kA rating is transferred by magnetic induction?
For an ideal 2-winding transformer, the ampere-turns of the primary winding, N1I1 is equal to the ampere-turns of the secondary winding, N2I2 (a) True (b) False
An ideal transformer has no real or reactive power loss. (a) True (b) False
A two-winding single-phase transformer rated 60kVA,240/1200V,60Hz, has an efficiency of 0.96 when operated at rated load, 0.8 power factor lagging. This transformer is to be utilized as a 1440/1200-V step-down autotransformer in a power distribution system. (a) Find the permissible kVA rating of the autotransformer if the winding currents and voltages are not to exceed the ratings as a two-winding transformer. Assume an ideal transformer. (b) Determine the efficiency of the autotransformer with the kVA loading of part (a) and 0.8 power factor leading.
A single-phase 100-kVA,2400/240-volt,60-Hz distribution transformer is used as a step-down transformer. The load, which is connected to the 240-volt secondary winding, absorbs 60 kVA at 0.8 power factor lagging and is at 230 volts. Assuming an ideal transformer, calculate the following: (a) primary voltage, (b) load impedance, (c) load impedance referred to the primary, and (d) the real and reactive power supplied to the primary winding.
Consider a bank of this single-phase two-winding transformers whose high-voltage terminals are connected to a three-phase, 13.8-kV feeder. The low-voltage terminals are connected to a three-phase substation load rated 2.0 MVA and 2.5 kV. Determine the required voltage, current, and MVA ratings of both windings of each transformer, when the high-voltage/low- voltage windings are connected (a) Y-, (b) -Y, (c) Y-Y, and (d) -.
A single-phase 50-kVA,2400/240-volt,60-Hz distribution transformer is used as a step-down transformer at the load end of a 2400-volt feeder whose series impedance is (1.0+j2.0) ohm. The equivalent series impedance of the transformer is (1.0+j2.5) ohms referred to the high-voltage (primary) side. The transformer is delivering rated load at a 0.8 power factor lagging and at a rated secondary voltage. Neglecting the transformer exciting current, determine (a) the voltage at the transformer primary terminals, (b) the voltage at the sending end of the feeder, and (c) the real and reactive power delivered to the sending end of the feeder.
Reconsider Problem 3.64 with the change that now Tb includes both a transformer of the same turns ratio as Ta and a regulating transformer with a 4 phase shift. On the base of Ta, the impedance of the two comp onents of Tb is jO.1 per unit. Determine the complex power in per unit transmitted to the load through each transformer. Comment on how the transformers share the real and reactive pors.