A 40 KVA, single phase transformer has 400 turns on the primary and 100turns on the secondary. The primary is connected to 2000V, 50 Hz supply.Determine:

i. The secondary voltage and

ii. The maximum value of flux.

Q.1

Full load efficiency of a 4,000/400V, 40 kVA, Single Phase Transformer is 94%.Maximum efficiency occurs at 90% of the full-load: Find Iron loss and full-loadcopper loss of the Transformer. The load power factor being 0.8 lagging. [10]

Q2

former is 98% both at full load and half load. The power factor on no-load is0.2 and the full load regulation at lagging power factor of 0.8 is 4%. Draw the

The efficiency, at unity power factor, of a 6600/384V, 200kVA, 1-phase trans-

equivalent circuit referred to L.V. side and insert all values.

Q3.

, 2000/400V, Transformer has iron and full load copper losses of 200

watts and 800 watts respectively. Calculate the efficiency at 1/4Φ

th full load and at 0.8 A 100 KV A, 1-

power factor.

Q4.

results,No-load Test: 200 V, 0.7A, 60W (L.V.side)S.C.Test : 9V, 6A, 21.6W (R.V Side)

Find the efficiency, and voltage regulation of the Transformer on full load at

A 4 KV A, 200/400V, 50 HZ, single phase transformer gave the following testQ5.

0.9 P.F.Lagging

Define regulation of a transformer. Derive the expression for the regulation

Discuss the constructional features of transformers. Draw neat diagrams.[8+8]

Q6.

o.c test 120V 4.2A 80W L.V.sides.c test 9.65V 22.2A 120W H.V.side

Determine

A 10KVA ,450/120V , 50 Hz, transformer gave the following data:Q7.

(a) equivalent circuit constants.

(b) efficiency and regulation for 80% lagging p.f load

−Φ transformer has 360 turns on the primary and 180 turns on the sec-ondary. The respective resistance are 0.233Ω aND 0.067Ω. Calculate theequivalent resistance of

i. the primary in terms of secondary windings

ii. the secondary in terms of primary windings

A 1Q8.

iii. the total resistance of the transformer in terms of primary.

(c) efficiency at half full load and 80% lagging p.f load.s.sree

kanth

a red

dy

sreekantha.292@gmail.com 04/19/2014

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[500 volts][0.0225 web]

[ans:-iron loass=919 watts,full load cu losses=1134.56 watts].

(b) Derive the expression for output KVA corresponding to the maximum effi-ciency of a 1-φ transformer. [8+8]

(a) Derive the condition for maximum efficiency.Q9.

No-load : Low voltage data : 200V, 0.7A, 60WShort Circuit : High voltage data : 9V, 6A, 21.6WCalculate:

(a) the magnetizing current and the component corresponding to iron loss atnormal frequency and voltage

A 4 KVA, 200/400V, 50Hz single phase transformer gave the following test results:Q10.

(b) the efficiency on full load at unity power factor

(c) the secondary terminal voltage on full load at power factors of unity, 0.8lagging and 0.8 leading.

φ transformer has an efficiency of 92 % both at full load andhalf full load at unity power factor. Determine its efficiency at 60% of fullload and 0.8 lagging power factor.

A 600 KVA, 1-Q11.

φ transformer gave the following test results :OC test : 200 V applied to primary, power absorbed is 72 WSC test : 8 V applied to primary, full load current in short circuited secondary,power absorbed is 80 W. Calculate efficiency at:

(a) full load at 0.9 pf lagging (b) half load at 0.9 pf lagging.

A 5 KVA, 200/400V, 1-Q12.

R0 =400Ω, X0 = 231Ω, Rt = 0.16ΩandXt = 0.7Ω. The input voltage is 200 V,and load 5.96 + j4.44Ω. (All values are referred to primary.) The ratio ofsecondary to primary turns is 10. Find the secondary terminal voltage; the

The parameters of the equivalent circuit for a 1-phase transformer areQ13.

96.97% at 0.8 p.f. lagging. It has a core loss of 50 watts and the full loadregulation at 0.8 p.f. lagging is 5%. Find the efficiency and regulation at full

primary current; and the efficiency.

load 0.9 p.f. lagging.

A 5 kVA, 220 / 110 volts, 1-phase transformer has a maximum efficiency ofQ14.

Explain with neat circuit diagrams, the open circuit and short circuit tests tobe carried out in the laboratory on a 1.5 kVA, 230 V / 40 V, 50 Hz, 1-phasetransformer, for the determination of the parameters of the equivalent circuit.

Q15.

Derive the emf equation of a 1-Phase transformer and calculate the emf / turn,if the flux is 0.015 wb at a frequency of 50 Hz.

Q16.

During experimentation on a 5 KVA transformer, it was found that the iron losses and full load copper losses are 100 and 200 watts respectively. Find these losses at half load and ¾ load.

Q17.

A single phase transformer has 400 primary and 1600 secondary form. The net cross –sectional area of the core is 55 cm2. If the primary winding is corrected to 220v, 50Hz 1-Φ supply, calculate maximum value of the x density in the core and its voltage induced in the secondary winding.

Q18.

s.sree

kanth

a red

dy

sreekantha.292@gmail.com 04/19/2014

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