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Star/star transformers work satisfactorily when?
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Mar 19, 2018
by
anonymous
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answered
Mar 19, 2018
by
anonymous
Star/star transformers work satisfactorily when
load is balanced .
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asked
Mar 19, 2018
by
anonymous
Delta/star transformer works satisfactorily when?
Last answer:
Delta/star transformer works satisfactorily when on balanced as well as unbalanced loads.
transformer
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1
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asked
Jul 27, 2019
by
anonymous
State and justify which of the following two transformers is better: Transformer A = 4% voltage regulation Transformer B = 6% voltage regulation
State and justify which of the following two transformers is better: Transformer A = 4% voltage regulation Transformer B = 6% voltage regulation
Last answer:
Transformer A with 4% voltage regulation is better. Justification: Voltage regulation refers to the percentage change in secondary voltage when load is changed from no-load to full-load with primary voltage ... 4% voltage regulation, which is less as compared to 6% of transformer B, it is better.
transformer
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102
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1
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asked
Mar 19, 2018
by
anonymous
Transformer breaths in when?
Last answer:
Transformer breaths in when load on it decreases.
transformer
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67
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1
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asked
Mar 19, 2018
by
anonymous
When a given transformer is run at its rated voltage but reduced frequency, its?
Last answer:
When a given transformer is run at its rated voltage but reduced frequency, its core flux density is increased.
transformer
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1
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asked
Mar 19, 2018
by
anonymous
When secondary of a current transformer is open-circuited its iron core will be?
When secondary of a current transformer is open-circuited its iron core will be?
Last answer:
When secondary of a current transformer is open-circuited its iron core will be hot because of heavy iron losses taking place in it due to high flux density.
secondary
current
transformer
open-circuited
iron
core
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asked
Apr 29, 2018
by
anonymous
If an unsymmetrical line to ground fault occurs at the secondary terminals of a delta/star, ungrounded
If an unsymmetrical line to ground fault occurs at the secondary terminals of a delta/star, ungrounded transformer, then (A) zero sequence currents are present on both sides of the transformer (B) zero sequence currents are absent on both sides of the transformer (C) zero sequence currents are present on the secondary side but not on the primary side (D) zero sequence currents are present on the primary side but not on the secondary side
Last answer:
If an unsymmetrical line to ground fault occurs at the secondary terminals of a delta/star, ungrounded transformer, then zero sequence currents are absent on both sides of the transformer
unsymmetrical
line
ground
fault
secondary
terminals
delta
star
transformer
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asked
Apr 28, 2018
by
anonymous
A 4000 kVA, 11 kV/132 kV delta-star connected 3-phase transformer has reactance, x1 = 0.12 p.u.
A 4000 kVA, 11 kV/132 kV delta-star connected 3-phase transformer has reactance, x1 = 0.12 p.u. The actual value of x1 referred to the low voltage side is (A) 0.85 Ω (B) 3.63 Ω (C) 36.3 Ω (D) 252 Ω
Last answer:
A 4000 kVA, 11 kV/132 kV delta-star connected 3-phase transformer has reactance, x1 = 0.12 p.u. The actual value of x1 referred to the low voltage side is 3.63 Ω
delta-star
transformer
reactance
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asked
May 7, 2020
by
anonymous
State the modification to be done in dc series motor to work satisfactorily as ac series motor. State applications of ac series motor.
State the modification to be done in dc series motor to work satisfactorily as ac series motor. State applications of ac series motor.
Last answer:
Modifications are necessary in a dc series motor so that it operates satisfactorily on ac supply. The modifications are as follows: 1) AC series motor is built with a few field turns as ... and grinders 5) High speed vacuum cleaners 6) Sewing machines 7) Food processors 8) Drilling machine
state
the
modification
to
be
done
in
dc
series
motor
work
satisfactorily
as
ac
applications
of
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79
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1
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asked
Mar 14, 2018
by
anonymous
Why does a transformer only work with an AC supply?
Why does a transformer only work with an AC supply?
Last answer:
The transformer work depends on the induction as main principle ,for that AC is the right means
transformer
only
work
ac
supply
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3
answers
asked
Dec 9, 2017
by
anonymous
why transformer don't work on DC supply?
why transformer don't work on DC supply?
Last answer:
A DC current does not produce a changing magnetic field which is capable of inducing current on the secondary windings of a transformer through mutual induction process.
transformer
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2
answers
asked
May 22, 2020
by
anonymous
Explain the effect of Harmonics on the Transformer.
Explain the effect of Harmonics on the Transformer.
Last answer:
Effect of Harmonics on the Transformer: 1. Core loss: Harmonic voltage increases the hysteresis and eddy current losses in the lamination. The amount of the core loss depends on ... small core vibrations. 5. Saturation problem: Sometimes additional harmonic voltage causes core saturation.
harmonics
transformer
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1
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asked
May 22, 2020
by
anonymous
List two special feature of welding transformer.
List two special feature of welding transformer.
Last answer:
Special features of welding transformer: i) It is a step down transformer that reduces the source voltage to a voltage desired according to the demands of the welding process. ii) Having large primary turns and less ... V ii) Secondary voltage - 40 to 60 V iii) Secondary current - 200 to 600 A
special
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welding
transformer
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asked
May 22, 2020
by
anonymous
State two applications of isolation transformer
State two applications of isolation transformer
Last answer:
Applications of isolation transformer: i) Isolates the load equipment from supply ground: ii) Reduction of voltage spikes iii) It acts as a decoupling device. iv) Protects loads from harmonic distortion.
applications
isolation
transformer
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1
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asked
May 22, 2020
by
anonymous
State why a transformer always have an efficiency of more than 90%.
State why a transformer always have an efficiency of more than 90%.
Last answer:
As transformer is static device with no moving parts, the losses due to friction & windage are completely absent. Hence transformer has efficiency of more than 90%.
transformer
efficiency
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asked
May 17, 2020
by
anonymous
Equivalent circuit of transformer
Equivalent circuit of transformer
Last answer:
Equivalent Circuit Diagram of Transformer Referred to Primary: V1 -Primary Input voltage I1 - Input Current I0- Exciting current/ No load current Im- Magnetizing component ... equivalent of secondary terminal voltage ZL- Load impedance ZL ′- Primary equivalent of load impedance
equivalent
circuit
transformer
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2
answers
asked
May 16, 2020
by
anonymous
Single phase transformer
Single phase transformer
Last answer:
Single phase Transformer Transformer
single
phase
transformer
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1
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asked
May 15, 2020
by
anonymous
What is the use of transformer?
What is the use of transformer?
Last answer:
The use of transformer is to do lower or raise the voltage or currents in an electrical circuit. That's quite so simple.
use
transformer
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139
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1
answer
asked
May 10, 2020
by
anonymous
Transformer on DC
Write about transformer on DC.
Last answer:
Transformer on DC : Transformer cannot work on DC. Transformer works on electromagnetic induction principle. Electromagnetic induction principle means when flux linking with coil changes and EMF induced in it ... winding insulation will burn. https://youtu.be/TVp_0fIfxqY
transformer
on
dc
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asked
Apr 28, 2020
by
anonymous
Even at no-load, a transformer draws current from the mains. Why?
Even at no-load, a transformer draws current from the mains. Why?
even
at
no-load
a
transformer
draws
current
from
the
mains
why
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answers
asked
Jul 27, 2019
by
anonymous
State any four characteristics of core type transformer.
State any four characteristics of core type transformer.
Last answer:
Characteristics of core type transformer: i) It has one window. ii) It has one magnetic circuit. iii) Core surrounds the winding. iv) Average length of core is more. v) Area of cross ... Better cooling for winding. vii) Mechnical strength is comparatively less. viii) Repair and maintenance is easy.
core
type
transformer
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1
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asked
Jul 26, 2019
by
anonymous
Explain construction and working of single phase Auto transformer.
Explain construction and working of single phase Auto transformer.
Last answer:
Construction of single phase auto transformer: (i) It has only one winding wound on a laminated circular magnetic core. (ii) The core is made of silicon steel stampings. (iii) The two terminals of the ... help of handle. 5) The same transformer can be used as step-up or step down auto-transformer
transformer
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1
answer
asked
Mar 19, 2018
by
anonymous
No-load current in a transformer?
Last answer:
No-load current in a transformer lags behind the voltage by about 75°.
transformer
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1
answer
asked
Mar 19, 2018
by
anonymous
The purpose of providing an iron core in a transformer is to?
Last answer:
The purpose of providing an iron core in a transformer is to decrease the reluctance of the magnetic path.
transformer
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1
answer
asked
Mar 19, 2018
by
anonymous
In the transformer which winding has got more cross-sectional area?
Last answer:
In the transformer low voltage winding has got more cross-sectional area.
transformer
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asked
Mar 19, 2018
by
anonymous
A transformer cannot raise or lower the voltage of a D.C. supply because?
Last answer:
A transformer cannot raise or lower the voltage of a D.C. supply because Faraday's laws of electromagnetic induction are not valid since the rate of change of flux is zero.
transformer
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1
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asked
Mar 19, 2018
by
anonymous
Primary winding of a transformer?
Last answer:
Primary winding of a transformer could either be a low voltage or high voltage winding.
transformer
primary
winding
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asked
Mar 19, 2018
by
anonymous
Which winding in a transformer has more number of turns ?
Last answer:
High voltage winding in a transformer has more number of turns.
transformer
turns
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1
answer
asked
Mar 19, 2018
by
anonymous
Efficiency of a power transformer is of the order of?
Last answer:
The efficiency of a power transformer is of the order of 98 percent.
transformer
efficiency
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1
answer
asked
Mar 19, 2018
by
anonymous
The no load current in a transformer lags behind the applied voltage by an angle of about?
Last answer:
The no load current in a transformer lags behind the applied voltage by an angle of about 75°.
transformer
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1
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asked
Mar 19, 2018
by
anonymous
In a transformer routine efficiency depends upon?
Last answer:
In a transformer, routine efficiency depends upon load current and power factor of load.
transformer
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1
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asked
Mar 19, 2018
by
anonymous
The maximum efficiency of a distribution transformer is?
Last answer:
The maximum efficiency of a distribution transformer is at 50% full load.
transformer
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1
answer
asked
Mar 19, 2018
by
anonymous
No-load current of a transformer has?
Last answer:
No-load current of a transformer has small magnitude and low power factor.
transformer
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1
answer
asked
Mar 19, 2018
by
anonymous
Spacers are provided between adjacent coils?
Last answer:
Spacers are provided between adjacent coils to provide free passage to the cooling oil.
transformer
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202
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1
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asked
Mar 19, 2018
by
anonymous
Greater the secondary leakage flux?
Last answer:
Greater the secondary leakage flux less will be the secondary induced e.m.f.
transformer
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1
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asked
Mar 19, 2018
by
anonymous
The purpose of providing iron core in a step-up transformer is?
Last answer:
The purpose of providing iron core in a step-up transformer is to decrease the magnitude of magnetizing current.
transformer
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290
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1
answer
asked
Mar 19, 2018
by
anonymous
The power transformer is a constant?
Last answer:
The power transformer is a constant main flux device.
transformer
power
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asked
Mar 19, 2018
by
anonymous
In a transformer the tappings are generally provided on?
Last answer:
In a transformer, the tappings are generally provided on low voltage side.
transformer
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1
answer
asked
Mar 19, 2018
by
anonymous
The use of higher flux density in the transformer design?
Last answer:
The use of higher flux density in the transformer design reduces weight per kVA.
transformer
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1
answer
asked
Mar 19, 2018
by
anonymous
The chemical used in breather for transformer should have the quality of?
Last answer:
The chemical used in breather for transformer should have the quality of cleansing the transformer oil.
transformer
breather
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96
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1
answer
asked
Mar 19, 2018
by
anonymous
The chemical used in breather is?
Last answer:
The chemical used in breather is silica gel.
breather
transformer
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54
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1
answer
asked
Mar 19, 2018
by
anonymous
An ideal transformer has infinite values of primary and secondary inductances. The statement is?
Last answer:
An ideal transformer has infinite values of primary and secondary inductances. The statement is false.
transformer
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asked
Mar 19, 2018
by
anonymous
The transformer ratings are usually expressed in terms of?
Last answer:
The transformer ratings are usually expressed in terms of kVA.
transformer
rating
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212
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asked
Mar 19, 2018
by
anonymous
Material used for construction of transformer core is usually?
Last answer:
Material used for construction of transformer core is usually silicon steel.
transformer
core
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asked
Mar 19, 2018
by
anonymous
The thickness of laminations used in a transformer is usually?
Last answer:
The thickness of laminations used in a transformer is usually 0.4 mm to 0.5 mm.
transformer
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1
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asked
Mar 19, 2018
by
anonymous
The function of conservator in a transformer is?
Last answer:
conservator or a reservoir tank for insulating oil in transformer which used for balanced the onload oil level with help of oil level indicator which mount on middle part of reservoir tank.
transformer
conservator
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3
answers
asked
Mar 19, 2018
by
anonymous
A transformer oil must be free from?
Last answer:
A transformer oil must be free from moisture.
transformer
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asked
Mar 19, 2018
by
anonymous
Gas is usually not liberated due to dissociation of transformer oil unless the oil temperature exceeds?
Last answer:
Gas is usually not liberated due to dissociation of transformer oil unless the oil temperature exceeds 150°C.
transformer
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asked
Mar 19, 2018
by
anonymous
The main reason for generation of harmonics in a transformer could be?
Last answer:
The main reason for generation of harmonics in a transformer could be saturation of core.
transformer
harmonics
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Mar 19, 2018
by
anonymous
The magnetising current of a transformer is usually small because it has?
Last answer:
The magnetising current of a transformer is usually small because it has small air gap.
transformer
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asked
Mar 19, 2018
by
anonymous
The leakage flux in a transformer depends upon?
Last answer:
The leakage flux in a transformer depends upon load current.
transformer
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