Transformers

The secondary current of a 20 KV/7.79 KV autotransformer is 100 amperes. Determine the current that flows through the common winding.

In a T-T connected transformer, if the terminal voltage in the primary side is 220 volts, what is the voltage across the teaser transformer?

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?

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.

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

Three units of 1:10 Transformers are connected in ∆/Y to supply a 3-phase load from a 400-v, 3-phase source. What is the line voltage on the load side?

A 10:1 ideal transformer has a load of 0.1μF on the secondary. What is the load capacitance, as referred to the primary?

A 50-kVA single-phase transformer has on full-load a copper loss of 560 watts and iron loss of 500 watts. Calculate the efficiency at 25% of full-load for a power factor of 0.8 lagging.

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?

A power transformer rated 50MVA, 34.5kV/13.8 kV is connected wye-wye. What is the rated primary line current?

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?

What will happen to the current of a transformer when the temperature of the transformers winding increases?

Transformers are used to change the value of the following EXCEPT

When a V-V system is converted into Δ-Δ system, increase in the capacity of the system is _____ percent.

The applied voltage in a transformer is increased by 50 % and frequency is reduced by 50 %. The maximum core flux density will become ______________.

A transformer has 4 % resistance and 6 % reactance drop. Find the voltage regulation at full-load 0.8 p.f. lagging.

A 13.8 kV/440 V, 50 kVA single-phase transformer has a leakage reactance of 300 ohms referred to the 13.8 kV side. Determine the per unit value of the leakage reactance on the low voltage base.

Compute for the core loss if the transformer consumes 75 watts when it is connected across a 240 v source and taking 1.4 A. The primary resistance is 0.25 Ω

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

Which is not a characteristic of an ideal transformer?