EE - Transformers

A 5 KVA, 2,300/460 V 2 winding transformer is to be connected as an auto-transformer to step-up the voltage from 2,300 V to 2,760 V. When used to transform 5 KVA, calculate the KVA load output.

A 100 MVA, 230/2.4 KV, 3 phase transformer with 2% resistance and 10% reactance is operating full load at 0.8 pf lagging. Find the % VR at the given load.

A 69/13.8 KV, 7.5 MVA, 3 phase transformer has 8% impedance. What is the transformer percent impedance at 100 MVA base?

A single phase transformer is rated 1 KVA, 220/110 V, 60 Hz. Because of an emergency, the transformer has to be used on a 50 Hz system. If the flux in the transformer is to be kept constant, what is the new KVA rating of transformer?

A 100 KVA, 14/2.4 KV, single phase transformer is supplied through a line with 38 + j140 ohms impedance. The transformer impedance referred to the secondary is 0.01 + j0.04 per unit. A load of 90 KW at 0.9 pf lag is connected to the secondary terminals. Find the supply voltage in volts if the voltage at the load side is 2.3 KV.

A 13.8/0.44 KV, 50 KVA, single phase transformer has a leakage reactance of 190 ohms referred to the primary side. Determine the per unit value of the leakage reactance referred to the low voltage side.

A 50 KVA, single phase transformer with ordinary efficiency of 96% at full load operates 8 hours/day to burn street lights. Determine the all day efficiency of the transformer if copper loss is 60% of the full load losses.

Two transformer, each rated at 100 kVA, 13.2/23 kV, 60 Hz are connected in open delta on the primary and secondary sides. What is the total load that can be supplied from this transformer bank in kVA?

The primary of the transformer has 200 turns and is excited by 240 turns and is excited by a 240 v, 60 Hz source. What is the maximum value of the core flux?

A 5:1 ratio ideal transformer has a rated primary line voltage of 230 V. If a load impedance of 4Ω is connected across the secondary, what will be the primary impedance?

A certain four-terminal transmission device has a characteristic impedance of 600 ohms and a propagation constant of 0.5 + j1.0. When terminated with its characteristic impedance, the ratio of the input voltage to the output voltage is what?

A single phase transformer is rated 110/440v, 2.5 kVA leakage reactance measured from the low-tension side is 0.06Ω. Determine leakage reactance in per unit.

A transformer is rated at 11 kV/0.4 kV, 500 kVA, 5% reactance. Determine the short circuit MVA of the transformer when connected to an infinite bus.

It is desired to step down the three-phase voltage from 6600 to 480 volts using Y – Δ transformer connection, What should be the ratio of transformation from transformer?

A transformer has a core loss of 64 watts and a copper loss of 144 watts when it is carrying 20% overload current. The load at which this transformer will operate at the maximum efficiency is percent.