Transformers

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?

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?

A transformer has negligible resistance and a p.u. reactance of 0.1. What is its voltage regulation on full load with a leading p.f. angle of 30°?

The output current corresponding to maximum efficiency for a transformer having a core loss of 100 watts and an equivalent resistance referred to the secondary of 0.25 Ω is ________ amperes.

If the copper loss of a transformer at 7/8 of full load is 4,900 W, what is its full-load copper loss?

Two transformers are connected in open delta and deliver a balanced three-phase load of 245 kW at 460 volts and a power factor of 0.707. Calculate the power delivered by the individual transformers.

A 20 kV/7.87 kV autotransformer has a secondary line current of 100 A. What is the current in the common winding?

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.

A 20 KV/7.87 KV autotransformer has a secondary line current of 100 A. What is the current in the common winding?

Two single-phase, 25-kVA transformers are connected in an open-delta bank. Determine the maximum kW the bank can supply without overloading at 0.8 p.f. lagging.

Three 1:1 transformer units connected Δ/Y supply a 3-phase load from a 400 volt, 3-phase source. What is the line voltage on the load side?