Two single phase transformers with equal ratings and turns ration are operated in parallel to supply a load of 300 KVA, 0.80 lagging power factor. Transformer A has a resistance of 2.5% and reactance of 5.5%. Transformer B has a resistance of 2.0% and a reactance of 5.5%. Find the KVA load of each transformer.
A147.7,152.2
B148.7,151.5
C149.7,150.5
D150.7,149.5
#62📜 EE Pre-Board March 2015📘 PowerhouseMedium
The core loss of a 5 KVA single phase transformer with normal voltage applied to the primary is 75 watts. The maximum efficiency occurs 60% of full load KVA. What is the full load efficiency of the transformer at 0.80 power factor?
A95.16%
B93.38%
C89.52%
D91.36%
#63📜 EE Pre-Board March 2015📘 PowerhouseMedium
The secondary current of a 20 KV/7.79 KV autotransformer is 100 amperes. Determine the current that flows through the common winding.
A60 amps
B100 amps
C79 amps
D50 amps
#64📜 EE Pre-Board August 2015📘 PowerhouseMedium
A 13.8 kV/480 V, 30-MVA three-phase transformer has a 0.03 pu resistance and 0.04 pu reactance. What is the transformer actual impedance referred to the primary?
A0.3174 Ω
B0.6348 Ω
C0.1587 Ω
D0.2749 Ω
#65📜 EE Pre-Board August 2015📘 PowerhouseMedium
A 20 kVA, 2000/220 V, single-phase transformer has a primary resistance of 2.1 Ω and a secondary resistance of 0.026 Ω. The corresponding leakage reactances are 2.5 Ω and 0.03 Ω. Determine the transformer per unit impedance.
A0.065 pu
B0.043 pu
C0.033 pu
D0.055 pu
#66📜 EE Pre-Board August 2015📘 PowerhouseMedium
The core loss of a 5-kVA single-phase transformer with normal voltage applied to the primary is 75 watts. The maximum efficiency occurs 60% of full- load kVA. What is the full-load efficiency of the transformer at 0.80 power factor?
A95.16%
B93.38%
C89.52%
D91.36%
#67📜 EE Pre-Board March 2016📘 PowerhouseMedium
A three phase wye delta connected, 50MVA, 345/ 34.5 Kv transformer is protected by differential protection. The current transformer on the high side for differential protection is 150:5. What is the current on the secondary side of CT’s?
A3.83A
B2.53A
C4.50A
D4.83A
#68📜 EE Pre-Board August 2017📘 PowerhouseMedium
A 20 kV/7.87 kV autotransformer has a secondary line current of 100 A. What is the current in the common winding?
A39.35 A
B60.65 A
C100 A
D139.35 A
#69📜 EE Pre-Board August 2017📘 PowerhouseMedium
Three 30:1 step-down transformers are connected Y–Δ for stepping down the 132,000 volt three-phase transmission voltage. Calculate the secondary line voltage.
A4,400 V
B7,621 V
C2,540 V
D1,467 V
#70📜 EE Pre-Board March 2018📘 PowerhouseMedium
A 20 KV/7.87 KV autotransformer has a secondary line current of 100 A. What is the current in the common winding?
A139.25 A
B100 A
C60.65 A
D39.35 A
#71📜 EE Pre-Board August 2018📘 PowerhouseMedium
A transformer is rated 10kVA, 440/110V and 60 Hz when operated as conventional 2 winding transformer. This transformer is to be used as 550/440 V step-down autotransformer in a distribution system. What is the new kVA rating of the transformer in this manner?
