GATE EE

Transformers

Electrical Machines

(Past Years Questions)

Marks 1

More
A single-phase 100 kVA, 1000 V / 100 V, 50 Hz transformer has a voltage drop of 5% across its series impedance at full l...
GATE EE 2018
The following figure shows the connection of an ideal transformer with primary to secondary turns ratio of 1 : 100. The ...
GATE EE 2016 Set 2
If an ideal transformer has an inductive load element at port 2 as shown in the figure below, the equivalent inductance ...
GATE EE 2016 Set 1
The self inductance of the primary winding of a single phase, 50 Hz, transformer is 800 mH, and that of the secondary wi...
GATE EE 2015 Set 1
Assuming an ideal transformer, The Thevenin's equivalent voltage and impedance as seen from the terminals x and y for th...
GATE EE 2014 Set 2
A single phase, 50 kVA, 1000 V/100 V two winding transformer is connected as an autotransformer as shown in the figure. ...
GATE EE 2014 Set 2
For a specified input voltage and frequency, if the equivalent radius of the core of a transformer is reduced by half, t...
GATE EE 2014 Set 1
A single-phase transformer has no-load loss of 64 W, as obtained from an open circuit test. When a short-circuit test is...
GATE EE 2013
A single phase air core transformer, fed from a rated sinusoidal supply, is operating at no load. The steady state magne...
GATE EE 2011
A single-phase transformer has a turns ratio of 1:2, and is connected to a purely resistive load as shown in the figure....
GATE EE 2010
The single phase, $$50$$ $$Hz$$ iron core transformer in the circuit has both the vertical arms of cross sectional area...
GATE EE 2009
It is desired to measure parameters of $$230$$ $$V/115$$ $$V,$$ $$2$$ $$kVA$$, single-phase transformers. The following ...
GATE EE 2008
In a transformer, zero voltage regulation at full load is
GATE EE 2007
In transformers, which of the following statements is valid?
GATE EE 2006
Which three-phase connection can be used in a transformer to introduce a phase difference of 30° between its output and ...
GATE EE 2005
A single phase transformer has a maximum efficiency of 90% at full load and unity power factor. Efficiency at half load ...
GATE EE 2003
A 1 kVA, 230V/100V, single phase, 50 Hz transformer having negligible winding resistance and leakage inductance is opera...
GATE EE 2002
A single-phase transformer is to be switched to the supply to have minimum inrush current. The switch should be closed a...
GATE EE 2001
The core flux of a practical transformer with a resistive load
GATE EE 2001
In a constant voltage transformer (CVT), the output voltage remains constant due to
GATE EE 2000
If an ac voltage wave is corrupted with an arbitrary number of harmonics, then the overall voltage waveform differs from...
GATE EE 2000
The laws of electromagnetic induction (Faraday's and Lenz's law) are summarized in the following equation:
GATE EE 1998
The efficiency of a 100 kVA transform is 0.98 at full as well as at half load. For this transformer at full load the cop...
GATE EE 1998
The magnetizing current in a transformer is rich in
GATE EE 1998
The low voltage winding of a $$400/230V,$$ $$1$$-phase, $$50$$ $$Hz$$ transformer is to be connected to a $$25$$ $$Hz,$$...
GATE EE 1997
The function of oil in a transformer is
GATE EE 1996
Auto-transformer is used in transmission and distribution
GATE EE 1996
Keeping in view the requirement of parallel operation, which of the $$3$$-phase connections given below are possible?
GATE EE 1996
The percentage impedance of a 100 kVA, 11 kV/400V, delta/wye, 50 Hz transformer is 4.5%. For the circulation of half the...
GATE EE 1995
Supply to one terminal of a $$\triangle$$ - Y connected three-phase core type transformer which is on no-load, fails. As...
GATE EE 1995
When a transformers winding suffers a short-circuit, the adjoining turns of the same winding experience
GATE EE 1994
Two transformers of identical voltage but of different capacities are operating in parallel. For satisfactory load shari...
GATE EE 1994
Two transformers of the same type, using the same grade of iron and conductor materials, are designed to work at the sam...
GATE EE 1992
Two transformers of different $$kVA$$ ratings workings in parallel share the load in proportion to their ratings when th...
GATE EE 1992

Marks 2

More
A transformer with toroidal core of permeability $$\mu $$ is shown in the figure. Assuming uniform flux density across t...
GATE EE 2018
A 3-phase 900 kVA, 3 kV / $$\sqrt 3 $$ kV (Δ/Y), 50 Hz transformer has primary (high voltage side) resistance per phase ...
GATE EE 2018
If the primary line voltage rating is 3.3 kV (Y side) of a 25 kVA. $$Y-\triangle$$ transformer (the per phase turns rati...
GATE EE 2017 Set 2
A three-phase, three winding $$\triangle$$ / $$\triangle$$ / Y (1.1 kV/6.6 kV/400 V) transformer is energized from AC ma...
GATE EE 2017 Set 1
A single-phase, 2 kVA, 100/200 V transformer is reconnected as an auto-transformer such that its kVA rating is maximum. ...
GATE EE 2016 Set 2
Three single-phase transformers are connected to form a delta-star three-phase transformer of 110 kV/ 11 kV. The transfo...
GATE EE 2016 Set 2
A single-phase, 22 kVA, 2200 V/220 V, 50 Hz, distribution transformer is to be connected as an autotransformer to get an...
GATE EE 2016 Set 1
A single-phase 400 V, 50 Hz transformer has an iron loss of 5000 W at the condition. When operated at 200 V, 25 Hz, the ...
GATE EE 2016 Set 1
If the star side of the star-delta transformer shown in the figure is excited by a negative sequence voltage, then ...
GATE EE 2016 Set 1
Two three-phase transformers are realized using single-phase transformers as shown in the figure. The phase difference ...
GATE EE 2015 Set 2
A balanced (positive sequence) three-phase AC voltage source is connected to a balanced, star connected load through a s...
GATE EE 2015 Set 2
A three-winding transformer is connected to an AC voltage source as shown in the figure. The number of turns are as foll...
GATE EE 2015 Set 2
Two single-phase transformers T1 and T2 each rated at 500 kVA are operated in parallel. Percentage impedances of T1 and ...
GATE EE 2015 Set 1
A 200/400 V, 50 Hz, two-winding transformer is rated at 20 kVA. Its windings are connected as an auto-transformer of rat...
GATE EE 2015 Set 1
The mean thickness and variance of silicon steel laminations are 0.2 mm and 0.02 respectively. The varnish insulation is...
GATE EE 2014 Set 3
The parameters measured for a 220V/110V, 50 Hz, single-phase transformer are: Self inductance of primary winding = 45 mH...
GATE EE 2014 Set 3
The load shown in the figure absorbs 4 kW at a power factor of 0.89 lagging. Assuming the transformer to be ideal, the ...
GATE EE 2014 Set 3
An open circuit test is performed on 50 Hz transformer, using variable frequency source and keeping V/f ratio constant, ...
GATE EE 2014 Set 3
For a single phase, two winding transformer, the supply frequency and voltage are both increased by 10%. The percentage ...
GATE EE 2014 Set 2
The core loss of a single phase, 230/115 V, 50 Hz power transformer is measured from 230 V side by feeding the primary (...
GATE EE 2014 Set 1
The following arrangement consists of an ideal transformer and an attenuator which attenuates by a factor of 0.8. An ac ...
GATE EE 2013
A single phase 10 kVA, 50 Hz transformer with 1 kV primary winding draws 0.5 A and 55 W, at rated voltage and frequency,...
GATE EE 2012
A balanced star-connected and purely resistive load is connected at the secondary of a star-delta transformer as shown i...
GATE EE 2010
The figure above shows coil $$1$$ and $$2,$$ with dot markings as shown, having $$4000$$ and $$6000$$ turns respective...
GATE EE 2009
The figure above shows coil $$1$$ and $$2,$$ with dot markings as shown, having $$4000$$ and $$6000$$ turns respective...
GATE EE 2009
The star-delta transformer shown above is excited on the star side with balanced, $$4$$-wire, $$3$$-phase, sinusoidal ...
GATE EE 2009
The star-delta transformer shown above is excited on the star side with balanced, $$4$$-wire, $$3$$-phase, sinusoidal ...
GATE EE 2009
The circuit diagram shows a two-winding, lossless transformer with no leakage flux, excited from a current source, $$i(t...
GATE EE 2009
The circuit diagram shows a two-winding, lossless transformer with no leakage flux, excited from a current source, $$i(t...
GATE EE 2009
Three single-phase transformers are connected to form a $$3$$-phase transformer bank. The transformers are connected in ...
GATE EE 2008
The core of two-winding transformer is subjected to a magnetic flux variation as indicated in the figure. The induce...
GATE EE 2008
A single-phase $$50$$ $$kVA,$$ $$250$$ $$V/500V$$ two winding transformer has an efficiency of $$95\% $$ at full load, u...
GATE EE 2007
Two transformers are to be operated in parallel such that they share load in proportion to their $$kVA$$ ratings. The ra...
GATE EE 2006
A $$300$$ $$kVA$$ transformer has $$95\% $$ efficiency at full load $$0.8$$ $$pf$$ lagging and $$96\% $$ efficiency at ...
GATE EE 2006
A $$300$$ $$kVA$$ transformer has $$95\% $$ efficiency at full load $$0.8$$ $$pf$$ lagging and $$96\% $$ efficiency at ...
GATE EE 2006
The resistance and reactance of a 100 kVA 11000|400 V, $$\triangle$$ - Y distribution transformer are 0.02 and 0.07 pu r...
GATE EE 2004
A 50 kVA, 3300/230 V single-phase transformers is connected as an autotransformer shown in figure. The nominal rating of...
GATE EE 2004
A 500 kVA, 3-phase transformer has iron loses of 300 W and full load copper losses of 600 W. The percentage load at whic...
GATE EE 2004
Figure shows an ideal single-phase transformer. The primary and secondary coils are wound on the core as shown. Turns ra...
GATE EE 2003
Figure shows an ideal three-winding transformer. The three windings 1,2,3 of the transformer are wound on the same core ...
GATE EE 2003
Figure shows a $$\triangle$$ - Y connected 3-phase distribution transformer used to step down the voltage from 11000 V t...
GATE EE 2003
A 400V/200V/200V, 50 Hz three winding transformer is connected as shown in Figure. The reading of the voltmeter 'V' will...
GATE EE 2002
A 3-phase transformer has rating of 20 MVA, 220 kV (star) / 33 kV (delta) with leakage reactance of 12%. The transformer...
GATE EE 2001
The hysteresis loop of a magnetic material has an area of 5 cm2 with the scales given as 1 cm = 2 AT and 1 cm = 50 mWb. ...
GATE EE 2001
A 3-phase delta/star transformer is supplied at 6000 V on the delta-connected side. The terminal voltage on the secondar...
GATE EE 2000
A 10 kVA, 400 V/200 V, single phase transformer with a percentage resistance of 3% and percentage reactance of 6% is sup...
GATE EE 1999
A 400V/100V, 10 kVA two-winding transformer is reconnected as an autotransformer across a suitable voltage source. The m...
GATE EE 1999
The percentage resistance and percentage reactance of a 10 kVA, 400 V/200 V, 3-phase transformer are 2% and 10% respecti...
GATE EE 1999
A 10 kVA, 400 V/200 V single-phase transformers with 10% impedance draws a steady short circuit line current of
GATE EE 1999
The windings of a Q kVA, $$\frac{V_1}{V_2}$$ Volt, three-phase, Delta connected, core type transformer are reconnected t...
GATE EE 1999
A 50 Hz transformer having equal hysteresis and eddy current losses at rated excitation is operated at 45 Hz at 90% of i...
GATE EE 1998
A voltage $$V=400$$ sin $$314.16t$$ is applied to a $$1$$-phase transformer on no-load. If the no load current of the tr...
GATE EE 1997
A $$3$$-phase transformer bank consists of three identical $$2300/230$$ $$V,$$ $$15$$ $$kVA$$ single-phase transformers ...
GATE EE 1997
A $$220/440$$ $$V,$$ $$50$$ $$Hz$$ single phase transformer operates on $$220$$ $$V,$$ $$40$$ $$Hz$$ supply with seconda...
GATE EE 1993

Marks 5

More
In a single phase $$3$$ winding transformer the turns ratio for primary: secondary: tertiary windings is $$20:4:1.$$ Wit...
GATE EE 2002
A single phase $$6300$$ $$kVA,$$ $$50$$ $$Hz,$$ $$3300V/400V$$ distribution transformer is connected between two $$50$$ ...
GATE EE 2002
An ideal transformer has a linear $$B-H$$ characteristic with a finite slope and a turns ratio of $$1:1.$$ The primary o...
GATE EE 2001
Two single phase transformers $$A$$ and $$B$$ have the following parameters. Transformer $$A$$: $$400V/200V,$$ $$10$$ $...
GATE EE 1999
In a $$50$$ $$KVA,$$ $$11$$ $$KV/400$$ $$V$$ transformers, the iron and copper losses are $$500$$ $$W$$ and $$600$$ $$W$...
GATE EE 1998

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