Q3: At the parallel operation of three-phase transformers: a) Give an explanation for the following cases: i. Two-lamps are glow-up ii. Three-lamps are glow-up b) Two three-phase 11kV/ 380 V transformers are connected in parallel to serve a load of 36 kVA at unity power factor. The secondary side current for one transformer is 14.1 A, determine the load sharing for each transformer and the current of the other transformer.
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A: Referring to the given hints, the impedance of the secondary side seen from the primary side:
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A: 1) Star- delta connection First approximation
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A: (b): Given in the question: Turns ratio: N1N2=101 Voltage on the primary side is: V1 = 2400V Voltage…
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A: As per the guidelines of Bartley we supposed to answer first three subpart only.
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Q: Impedance of single phase., two winding transformer referred to primary side is 0.1 + j0.6 p.u. The…
A: Given values are - S=1kVAZPP.U=0.1+j0.6V1V2=200400
Q: Example: A single-phase, 100-kVA, 1000:100-V, 60-Hz transformer has the following test results:…
A: TRANSFORMER: The transformer transfers power from one circuit to another circuit without a change…
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Q: Q2: a) Determine the efficiency of three-phase 400 kVA, 11kV/ 380 V transformer at over-loading…
A: The efficiency of a three-phase transformer is determined as shown below
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Q: Example: A single-phase, 100-kVA, 1000:100-V, 60-Hz transformer has the following test results:…
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A: Following data is given in the question.
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Q: The efficiency of a 20 kVA 15.4 / 0.4 kV three-phase power transformer is 75.4% for a load with…
A: 1) The primary reduced equivalent circuit is as follows:
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Q: Open-circuit test Short-circuit test Voc = 480 V Vsc = 10.0 V loc = 0.41 A Isc = 10.6 A %3D Poc = 38…
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Q: 1. Why is it not adjustable to carry or the same experiment for large transformers? 2. What method…
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Q: The efficiency of a 20 kVA 15.4 / 0.4 kV three-phase power transformer is 74,1% for a load with…
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- In developing per-unit equivalent circuits for three-phase transformers. under balanced three-phase operation. (i) A common Sbase is selected for both the H and X terminals. (ii) The ratio of the voltage bases Vbase/VbaseX is selected to be equal to the ratio of the rated line-to-line voltages VratedHLL/VratedXLL. (a) Only one of the above is true. (b) Neither is true. (C) Both statements are true.(a) An ideal single-phase two-winding transformer with turns ratio at=N1/N2 is connected with a series impedance Z2 across winding 2. If one wants to replace Z2, with a series impedance Z1 across winding 1 and keep the terminal behavior of the two circuits to be identical, find Z1 in terms of Z2. (b) Would the above result be true if instead of a series impedance there is a shunt impedance? (c) Can one refer a ladder network on the secondary (2) side to the primary (1) side simply by multiplying every impedance byat2 ?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
- An ideal transformer has no real or reactive power loss. (a) True (b) FalseAn infinite bus, which is a constant voltage source, is connected to the primary of the three-winding transformer of Problem 3.53. A 7.5-MVA,13.2-kV synchronous motor with a sub transient reactance of 0.2 per unit is connected to the transformer secondary. A5-MW,2.3-kV three-phase resistive load is connected to the tertiary Choosing a base of 66 kV and 15 MVA in the primary, draw the impedance diagram of the system showing per-unit impedances. Neglect transformer exciting current, phase shifts, and all resistances except the resistive load.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.
- Consider the three single-phase two-winding transformers shown in Figure 3.37. The high-voltage windings are connected in Y. (a) For the low-voltage side, connect the windings in , place the polarity marks, and label the terminals a, b, and c in accordance with the American standard. (b) Relabel the terminals a, b, and c such that VAN is 90 out of phase with Va for positive sequence.A bank of three single-phase transformers, each rated 30MVA,38.1/3.81kV, are connected in Y- with a balanced load of three 1, Y-connected resistors. Choosing a base of 90MVA,66kV for the high-voltage side of the three-phase transformer. spify the base for the low-voltage side. Compute the per-unit resistance of the load on the base for the low-voltage side. Also, determine the load resistance in ohms referred to the high-voltage side and the per-unit value on the chosen base.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.
- 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.Consider a single-phase electric system shown in Figure 3.33. Transformers are rated as follows: XY15MVA,13.8/138kV, leakage reactance 10 YZ15MVA,138/69kV, leakage reactance 8 With the base in circuit Y chosen as 15MVA,138kV determine the per-unit impedance of the 500 resistive load in circuit Z, referred to circuits Z, Y, and X. Neglecting magnetizing currents, transformer resistances, and line impedances, draw the impedance diagram in per unit.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.