Transformers

A 250/6,600 V, 50 Hz single-phase transformer has a core of cross section 600 cm² and the flux density in it is 0.707 Tesla. Determine the number of turns in the primary winding.

If the secondary terminals of a 5:1 stepdown transformer is connected to the primary of a 2:1 stepdown transformer then the total stepdown ratio of both transformers is

A 2,000 V/ 400 V single phase transformer has an equivalent resistance of 0.03 pu and an equivalent reactance of 0.08 pu. Find the full load voltage regulation at 0.8 pf lagging if the primary voltage is 1,500 V.

Three units of 1:5 transformers are connected in Δ/Y to supply a 3 phase load from a 480 V, 3 phase source. The line voltage on the load side is _ volts.

A transformer has a maximum efficiency of 95% at a load of 100 kW. What is the constant loss of the transformer?

An amplifier works best into an impedance of 500 ohms but is required to drive a speaker of 20 ohms impedance. The primary to secondary turn ratio of the matching transformer should be

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

A transformer is rated 1 kVA, 220/110 V, 60 Hz. Because of an emergency this transformer has to be used on a 50 Hz system. If the flux density in the transformer core is to be kept the same as at 60 Hz and 220 V, what is the kilovolt-ampere rating at 50 Hz?

A commercial building with an aggregate three-phase load of 170 kVA is to be served using two single-phase transformers connected in V-V bank. What should be the minimum size of each transformer in kVA.

A 240 V to 120 V, 50 Hz step-down transformer is to be operated at 60 Hz. What is the highest safe input voltage?

The net cross section of a transformer is 20 square inches. The maximum flux density is 11 kilogausses. The frequency is 60 Hz. If there are 1,000 turns in the primary, determine the primary induced emf.

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

A transformer is to be used to match a secondary load impedance of 800 ohms to a generator line impedance of 128 ohms. What should be the ratio of transformation of the transformer for maximum power transfer?

The percentage overloading of two 20-kVA transformers when supplying a balanced 3Φ load of 40 kVA in a V-V bank is ______ percent.

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

Find the cross-sectional area of the core of a 10 turns transformer for a voltage of 50 v at 50 HZ. The flux density is 0.9 Wb/m² .

What should be the turns ratio of a three-phase transformer to transform 10,000 KVA from 230 KV to 4,160 V if the transformer is to be connected ∆-Y?

A 15 KVA, single-phase distribution transformer has a core and copper losses at rated condition of 90 w and 300 w, respectively. Determine its maximum efficiency at 0.707 power factor lagging.

A 10:1 single-phase transformer is rated 100 kVA 2,400/240 v. When the low voltage side of the transformer is maintained at 240 v, what is the secondary impedance? 0.676

A transformer has an impedance of 6%. The X/R ratio is 16. Find the per unit admittance G + jB.