Three-single phase transformers each rated $75$ kVA are banked in delta and supplying a $3$-phase load drawing $160$ kVA at $0.8$ lagging power factor. If one transformer is removed for repairs, solve for the amount of overloading of the remaining units.
A30 kVA
B10 kVA
C20 kVA
D25 kVA
#62📜 EE Board April 1992
A $6600$-volt, $60$ Hz, $2$-phase network is connected to a three-phase, $4$-wire system by a Scott-connected transformer combination. If there are $1500$ turns on the $2$-phase side, calculate the number of turns on the $3$-phase side required for the main and teaser transformers. Voltage per phase on the $3$-phase side is $240$ V.
A94 turns, 83 turns
B93 turns, 84 turns
C95 turns, 82 turns
D92 turns, 85 turns
#63📜 EE Board April 1985
A balanced $3$-phase transformer bank has delta-connected primary and wye-connected secondary windings. The primary to secondary winding voltage ratio is $2400/277$. Solve for the primary line current if the low-side (secondary) load draws a line current of $1000$ A.
A200 A
B115 A
C150 A
D175 A
#64
A three-phase $150$ kVA, $4160$ V, $0.8$ lagging pf load is to be supplied by three single-phase transformers having a turns ratio of $2$. Calculate the current that flows in the primary windings if the transformers are connected delta-delta.
A10.41 A
B6.01 A
C20.82 A
D12.02 A
#65📜 EE Board October 1991
What should be the turns ratio of a three phase transformer to transform $10000$ kVA from $230$ kV to $4160$ V if the transformer is to be connected $\Delta - Y$?
A94
B98
C96
D97
#66
A bank of three $50:1$ single-phase transformers connected Y-$\Delta$ is used to step down the HV transmission line rated $138$ kV. Determine the magnitude of the step down voltage.
A126 kV
B6.90 kV
C138.55 kV
D159.35 kV
#67📜 EE Board October 1998
The potential transformer of a line has a ratio $132000/66$. These are connected wye-delta. The voltmeter reads $64$ volts. What is the voltage of the line?
A221.7 kV
B112.5 kV
C135.2 kV
D132 kV
#68📜 EE Board October 1997
A power transformer rated $50000$ kVA, $34.5 \text{ kV}/13.8 \text{ kV}$ is connected wye-grounded primary and delta on the secondary. Determine the full load phase current on the secondary side.
A2092 A
B1725 A
C1449 A
D1208 A
#69📜 EE Board October 1998
A $69/13.8$ kV, $10$ MVA three-phase transformer is connected wye-grounded delta. What is the kV rating of the secondary winding?
A7.97
B15
C23.9
D13.8
#70📜 EE Board October 1997
The PTs of a $220$ kV transmission line have ratio of $132.76 \text{ kV}/66.375 \text{ kV}$ and are connected wye-wye. A voltmeter connected line to ground reads $66$ volts. What is the transmission line voltage?
A228.63 kV
B220.10 kV
C223.15 kV
D225.25 kV
#71📜 EE Board October 1997
A power transformer rated $50000$ kVA, $34.5 \text{ kV}/13.8 \text{ kV}$ is connected wye-wye. What are the line currents at full load?
A525.2 A, 1725.4 A
B836.7 A, 2092 A
C483.1 A, 1207.7 A
D1449.3 A, 3623.2 A
#72📜 EE Board October 1985
Two transformers are connected in parallel to supply a common load of $175$ kVA. Transformer A is rated $100$ kVA with equivalent impedance of $9.6$ ohms while transformer B is rated $75$ kVA with equivalent impedance of $12.5$ ohms. Find the kVA load of each transformer.
A78, 97
B76, 99
C80, 95
D75, 100
#73📜 EE Board October 1981
Two distribution transformers are connected in parallel supplying a load of $125$ kVA. If transformer A is rated $50$ kVA, with $14$ ohms equivalent reactance and transformer B is rated $75$ kVA with $11$ ohms equivalent reactance. Solve for the loading in kVA of each transformer.
A55 kVA, 70 kVA
B50 kVA, 75 kVA
C58 kVA, 67 kVA
D52 kVA, 73 kVA
#74📜 EE Board March 1998
A $125$-kVA distribution transformer with $4\%$ impedance is connected in parallel with another transformer rated $75$-kVA and with $3\%$ impedance. Both have the same voltage ratio. Neglect resistance of each transformer. The total load is $140$ kVA at $85$ percent power factor. How much load does each carry?
A80.5 kVA / 59.5 kVA
B77.78 kVA / 62.22 kVA
C80 kVA / 60 kVA
D87.5 kVA / 52.5 kVA
#75
Two parallel transformers have $8\%$ reactance each. One is rated $25$ MVA and the other at $15$ MVA. For a given $30$ MVA load with a lagging pf of $0.8$, Determine the load carried by each transformer?
A18.50 MVA, 11.50 MVA
B18.75 MVA, 11.25 MVA
C15.25 MVA, 14.75 MVA
D16.45 MVA, 13.55 MVA
#76
A $500$-kVA single-phase transformer "A" with percentage impedance of $0.010 + j0.05$ is connected in parallel with a $250$-kVA transformer "B" with a percentage impedance of $0.015 + j0.04$. If the transformers are serving a single-phase load rated $800$-kVA, $80\%$ lagging pf, determine the operating pf of each transformer. Assume the transformers have the same turns ratio.
AA = 0.762, B = 0.803
BA = 0.772, B = 0.856
CA = 0.762, B = 0.856
DA = 0.772, B = 0.803
#77📜 EE Board April 1993
The MERALCO has two single-phase transformers with equal turns ratio and ratings and are operated in parallel to supply a load of $280$ kW at $0.80$ lagging pf. Transformer A has a resistance of $2\%$ and a reactance of $8\%$. Transformer B has a resistance of $1\%$ and a reactance of $6\%$. Determine the power delivered by the transformers A and B to the load.
AA = 123 kW, B = 157 kW
BA = 125 kW, B = 155 kW
CA = 122 kW, B = 158 kW
DA = 127 kW, B = 153 kW
#78📜 EE Board April 1994
Two single-phase transformers with equal ratings and turns ratio are operated in parallel to supply a load of $180$ kW at a lagging pf of $0.90$. Transformer A has a resistance of $1\%$ and a reactance of $6\%$. Transformer B has a resistance of $2\%$ and a reactance of $5\%$. Calculate the power delivered by each transformer.
A80 kW, 100 kW
B83 kW, 97 kW
C79 kW, 101 kW
D88 kW, 92 kW
#79
Two single-phase transformers A and B are connected in parallel to serve a $600$-A single-phase load at $0.80$ pf lagging. The equivalent impedance of the transformers are $2 + j3$ and $2.3 + j5$ ohms, respectively. Determine the ratio of the kW output of transformer A to the kW output of transformer B. Assume the transformers have equal ratings and turns ratio.
