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What is the back EMF in Transformers?
asked
Mar 15, 2018
by
anonymous
What is the back EMF in Transformers?
back
emf
transformers
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asked
Mar 15, 2018
by
anonymous
What is back EMF in inductor?
What is back EMF in inductor?
back
emf
inductor
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asked
Mar 15, 2018
by
anonymous
What is the back EMF of a dc motor?
What is the back EMF of a dc motor?
back
emf
dc
motor
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asked
Mar 15, 2018
by
anonymous
What is the back EMF of the motor?
What is the back EMF of the motor?
back
emf
motor
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asked
Mar 15, 2018
by
anonymous
What is the back EMF?
What is the back EMF?
Last answer:
When the armature of a d.c. motor rotates under the influence of the driving torque, the armature conductors move through the magnetic field and hence e.m.f. is induced in them as in a generator. The ... that energy conversion in a d.c. motor is only possible due to the production of back emf.
back
emf
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1
answer
asked
Apr 27, 2020
by
anonymous
What is back emf?
What is back emf?
Last answer:
Back EMF: When a current carrying conductor is placed in a magnetic field it experiences a force; when it moves due to the force it (conductor) cuts the magnetic field due to which an emf is ... (hence the applied armature voltage) is opposed by the induced emf which is therefore called as Back emf.
what
is
back
emf
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asked
Mar 15, 2018
by
anonymous
What is back EMF of synchronous motor?
What is back EMF of synchronous motor?
back
emf
synchronous
motor
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asked
Mar 15, 2018
by
anonymous
Do AC induction motors have back EMF?
Do AC induction motors have back EMF?
ac
induction
motors
back
emf
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answers
asked
Mar 18, 2018
by
anonymous
The back emf of synchronous motor depends on?
The back emf of synchronous motor depends on?
Last answer:
The back emf of synchronous motor depends on load angle.
back
emf
synchronous
motor
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1
answer
asked
Mar 20, 2018
by
anonymous
What will happen if the back e.m.f. of a D.C. motor vanishes suddenly?
Last answer:
The armature may burn if the back e.m.f. of a D.C. motor vanishes suddenly.
back
emf
dc
motor
vanishes
suddenly
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1
answer
asked
Mar 20, 2018
by
anonymous
In case of D.C. shunt motors the speed is dependent on back e.m.f. only because?
Last answer:
In case of D.C. shunt motors the speed is dependent on back e.m.f. only because flux is practically constant in D:C. shunt motors.
dc
shunt
motors
speed
back
emf
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1
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asked
Mar 20, 2018
by
anonymous
The mechanical power developed by a shunt motor will be maximum when the ratio of back e.m.f. to applied voltage is?
Last answer:
The mechanical power developed by a shunt motor will be maximum when the ratio of back e.m.f. to applied voltage is 0.5.
mechanical
power
shunt
motor
maximum
ratio
back
emf
voltage
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144
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1
answer
asked
Sep 7, 2018
by
anonymous
What is Phase sequence? Draw waveforms of 3 phase emf.
What is Phase sequence? Draw waveforms of 3 phase emf.
Last answer:
Phase sequence: It is the order in which the three phases reach their peak or maximum values. It is shown in below fig. the phase sequence is A-B-C (or R-Y-B). In the following waveforms, it is ... 120º, B- phase voltage attains its positive maximum value. So the phase sequence is R-Y-B.
phase
sequence
waveforms
emf
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1
answer
asked
Jan 15, 2018
by
James
of what use are current and voltage transformers in protective systems
Last answer:
Current transformers (CT) : Current transformer (CT) actually step down the high current to low current for the operation of relays. Current transformer is use for measurement of ... use for relay. This is about potential transformer.
relay-
transformers
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115
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1
answer
asked
Dec 22, 2017
by
anonymous
What is the EMF equation of the transformer?
What is the EMF equation of the transformer?
Last answer:
E1 =2(3.142)fN1 (flux)1E2 =2(3.142)fN2(flux)2
emf
equation
transformer
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123
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1
answer
asked
Mar 19, 2018
by
anonymous
What will happen if the transformers working in parallel are not connected with regard to polarity ?
Last answer:
Winding will be damaged
transformers
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2
answers
asked
Aug 13, 2019
by
Alacrity
the volt per turn of a certain single phase transformers is 1.7. the transformer has a step ratio of 3825/255volt. calculate the respective number of turns in each winding
single
phase
transformers
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asked
Apr 29, 2018
by
anonymous
Which of the following is the advantage of using CRGO steel in transformers?
Which of the following is the advantage of using CRGO steel in transformers? A) High magnetic flux density B) Low permeability C) Both A and B D) None of these
Last answer:
It definitely High Magnetic Flux Density since a crgo steel has always a more around 3% of silicon proportion among the remaining ferrite which make cold rolled grain oriented steel having high flux magnetic ... for more about the crgo core you can learn here https://nicoreindia.com/crgo-core/
crgo
steel
transformers
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79
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2
answers
asked
May 8, 2018
by
anonymous
The friction losses in Real Transformers are :
The friction losses in Real Transformers are : (A) 0% (B) 5% (C) 25% (D) 50%
Last answer:
A
friction
losses
real
transformers
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2.5k
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2
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asked
Aug 8, 2018
by
anonymous
Explain the term self induced EMF with a neat diagram.
Explain the term self induced EMF with a neat diagram.
self
induced
emf
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answers
asked
Aug 8, 2018
by
anonymous
List the two types of induced EMF.
List the two types of induced EMF.
Last answer:
There are two types of EMF one is statically induced EMF and second is dynamically induced EMF.
induced
emf
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1
answer
asked
Apr 29, 2018
by
anonymous
The induced emf in the armature of a lap -wound four -pole dc machine having 100 armature conductors
The induced emf in the armature of a lap -wound four -pole dc machine having 100 armature conductors rotating at 600 rpm and with 1 Wb flux per pole is (1) 1000V (2) 100V (3) 600V (4) 10,000V
Last answer:
The induced emf in the armature of a lap -wound four -pole dc machine having 100 armature conductors rotating at 600 rpm and with 1 Wb flux per pole is 1000V
induced
emf
armature
lap-wound
four-pole
dc
machine
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161
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1
answer
asked
Apr 30, 2018
by
anonymous
Two 3-phase transformers cannot be operated in parallel, if their :
Two 3-phase transformers cannot be operated in parallel, if their : (A) kVAs are different (B) phase sequences are different (C) % impedances are different (D) voltage ratios are different
Last answer:
Two 3-phase transformers cannot be operated in parallel, if their : phase sequences are different
3-phase
transformers
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1
answer
asked
Aug 17, 2019
by
anonymous
Self induced emf and Mutually induced emf
Self induced emf and Mutually induced emf
Last answer:
(i) Self-induced e.m.f.: The e.m.f. induced in a coil due to the change of its own flux linked with it, is called self-induced e.m.f. (ii) Mutually induced e.m.f.: The e.m.f. induced in a coil due to the changing current in the neighbouring coil, is called mutually induced e.m.f.
mutually
induced
emf
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1
answer
asked
Sep 4, 2018
by
anonymous
Compare statically induced emf with dynamically induced emf on any four points.
Compare statically induced emf with dynamically induced emf on any four points.
Last answer:
Statically induced emf Dynamically induced emf Emf is induced without any relative motion between conductor and magnetic field. Emf is induced due to relative motion between conductor ... induced in transformer windings e.g emf induced in Generator, Alternator armature windings
compare
statically
induced
emf
dynamically
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2
answers
asked
Aug 8, 2018
by
anonymous
Define: 1) statically induced EMF 2) dynamically induced EMF
Define: 1) statically induced EMF 2) dynamically induced EMF Write the names of equipments in which these two types of EMF get induced
Last answer:
Concept of statically induced emf: The emf induced in coil or conductors without any relative motion between it and magnetic field is called statically induced emf. When conductor is stationary and flux ... it. This emf is dynamically induced emf. e.g. Emf induced in generators, alternator.
statically
induced
emf
dynamically
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370
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3
answers
asked
Apr 28, 2018
by
anonymous
The fractional-pitch used for eliminating 7th harmonic from the emf wave of an alternator is
The fractional-pitch used for eliminating 7th harmonic from the emf wave of an alternator is (A) 2/3 (B) 5/6 (C) 7/8 (D) 6/7
Last answer:
The fractional-pitch used for eliminating 7th harmonic from the emf wave of an alternator is 6/7
fractional-pitch
7th
harmonic
emf
wave
alternator
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289
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1
answer
asked
Mar 19, 2018
by
anonymous
Two transformers do not have equal percentage impedance. This is likely to result in?
Two transformers are connected in parallel. These transformers do not have equal percentage impedance. This is likely to result in?
Last answer:
Two transformers are connected in parallel. These transformers do not have equal percentage impedance. This is likely to result in loading of the transformers not in proportion to their kVA ratings.
transformers
parallel
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69
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1
answer
asked
May 8, 2018
by
anonymous
Which of the following connection of transformers will give highest value of secondary voltage ?
Which of the following connection of transformers will give highest value of secondary voltage ? (A) Delta primary delta secondary (B) Delta primary star secondary (C) Star primary star secondary (D) Star primary delta secondary
Last answer:
Which of the following connection of transformers will give highest value of secondary voltage ? (A) Delta primary delta secondary (B) Delta primary star secondary (C) Star primary star secondary (D) Star primary delta secondary
connection
transformers
highest
value
secondary
voltage
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105
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1
answer
asked
Mar 19, 2018
by
anonymous
If the percentage impedances of the two transformers working in parallel are different, then?
Last answer:
If the percentage impedances of the two transformers working in parallel are different, then parallel operation will still be possible, but the power factors at which the two transformers operate will be different from the power factor of the common load.
transformers
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56
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1
answer
asked
May 8, 2018
by
anonymous
Two transformers A and B having equal outputs and voltage ratios but unequal percentage
Two transformers A and B having equal outputs and voltage ratios but unequal percentage impedances of 4 and 2 are operating in parallel. The transformer A will be overloaded by
Last answer:
Two transformers A and B having equal outputs and voltage ratios but unequal percentage impedances of 4 and 2 are operating in parallel. The transformer A will be overloaded by 33%
transformers
voltage
ratios
percentage
impedances
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195
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1
answer
asked
May 8, 2018
by
anonymous
Core type transformers are popular in___________.
Core type transformers are popular in___________. (A) High voltage applications (B) Low voltage applications (C) All of the above (D) None of the above
Last answer:
Core type transformers are popular in High voltage applications
core
type
transformers
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1
answer
asked
May 8, 2018
by
anonymous
In a transmission line if booster transformers are to be used, preferred location will be
In a transmission line if booster transformers are to be used, preferred location will be (A) At the receiving end (B) At the sending end (C) At the intermediate point (D) Anywhere in the line
Last answer:
In a transmission line if booster transformers are to be used, preferred location will be At the intermediate point
transmission
line
booster
transformers
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208
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1
answer
asked
Mar 19, 2018
by
anonymous
Losses which occur in rotating electric machines and do not occur in transformers are?
Losses which occur in rotating electric machines and do not occur in transformers are?
Last answer:
Friction losses windage losses
losses
rotating
electric
machines
transformers
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107
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2
answers
asked
Apr 27, 2020
by
anonymous
Explain dynamic and static induced emf with neat diagram.
Explain dynamic and static induced emf with neat diagram.
Last answer:
Dynamically Induced EMF:- In this case, either coil moves or magnet moves, so that there is relative motion between coil & magnetic field. Thus magnetic field is cut by coil & emf is induced in it. The emf ... The expression for induced EMF is e= -L(di/dt) or = -N(dϕ/dt).
explain
dynamic
and
static
induced
emf
with
neat
diagram
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93
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1
answer
asked
Dec 13, 2019
by
UMESH y
Emf definition
emf
definition
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117
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0
answers
asked
Mar 19, 2018
by
anonymous
For the parallel operation of single phase transformers it is necessary that they should have?
Last answer:
Necessary conditions required to be satisfied in order to ensure successful parallel operation of single phase transformers: 1. Only transformers having the same phase displacement between primary and secondary ... . 7. The phase sequence must be followed strictly on HV and LV side connection.
parallel
operation
single
phase
transformers
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111
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2
answers
asked
Apr 29, 2018
by
anonymous
An additional condition for parallel operation of three-phase transformers over single-phase transformers is that
An additional condition for parallel operation of three-phase transformers over single-phase transformers is that
Last answer:
An additional condition for parallel operation of three-phase transformers over single-phase transformers is that the transformers should belong to the same vector group
parallel
operation
three-phase
transformers
single-phase
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81
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1
answer
asked
Mar 19, 2018
by
anonymous
Natural oil cooling is used for transformers up to a rating of?
Last answer:
Natural oil cooling is used for transformers up to a rating of 3000 kVA.
transformers
cooling
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130
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1
answer
asked
Mar 19, 2018
by
anonymous
Short circuit test on transformers is conducted to determine?
Last answer:
Short circuit test on transformers is conducted to determine copper losses.
short
circuit
test
transformers
conducted
determine
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106
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1
answer
asked
Mar 19, 2018
by
anonymous
Natural air cooling is generally restricted for transformers up to?
Last answer:
Natural air cooling is generally restricted for transformers up to 1.5 MVA .
natural
air
cooling
restricted
transformers
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140
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1
answer
asked
Aug 30, 2018
by
anonymous
Classify the transformers based on the construction, frequency and power.
Classify the transformers based on the construction, frequency and power.
Last answer:
Classification of Transformer Based On: i) Construction: Shell type, Core type, Berry type ii) Change in voltage level: Step-Up, Step-Down, iii) Number of phases: Single phase, Three phase iv) ... Control vi) Cooling: Self-cooled, Air-cooled, Forced-air cooled, Oil-cooled, Forced-oil cooled.
classify
transformers
construction
frequency
power
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105
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1
answer
asked
Mar 19, 2018
by
anonymous
The efficiency of two identical transformers under load conditions can be determined by?
The efficiency of two identical transformers under load conditions can be determined by?
Last answer:
The efficiency of two identical transformers under load conditions can be determined by back-to-back test.
efficiency
identical
transformers
load
conditions
determined
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107
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1
answer
asked
Mar 19, 2018
by
anonymous
The efficiencies of transformers compared with that of electric motors of the same power are?
The efficiencies of transformers compared with that of electric motors of the same power are?
Last answer:
Transformers have high efficiency than the same ratted motors
efficiencies
transformers
electric
motors
power
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93
views
2
answers
asked
Mar 21, 2018
by
anonymous
Instrument transformers are?
Last answer:
Instrument transformers are potential transformers, current transformers.
instrument
transformers
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56
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1
answer
asked
Mar 19, 2018
by
anonymous
Distribution transformers are generally designed for maximum efficiency around?
Last answer:
Distribution transformers are generally designed for maximum efficiency around 50% load.
transformers
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90
views
1
answer
asked
Mar 19, 2018
by
anonymous
Power transformers are generally designed to have maximum efficiency around?
Last answer:
Power transformers are generally designed to have maximum efficiency around near full-load.
transformers
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74
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1
answer
asked
Dec 17, 2017
by
anonymous
Why do transformers make noise?
Why do transformers make noise?
Last answer:
Transformers make noise based on it out put if an transformer outputs is 400v maximum than a 398v be apply to that transformer it also make a noise because of that
transformers
noise
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72
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1
answer
asked
Sep 18, 2018
by
anonymous
What is back emf in DC motor? Explain its significance.
Last answer:
Back emf: When the armature of DC motor rotates under the fixed magnetic field and cuts it, by Faraday's law an emf is induced in them. The induced emf acts in opposite direction to the ... the flow of armature current i.e. it automatically changes the armature current to meet load requirements.
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45
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1
answer
asked
Jul 24, 2019
by
Deepak kumar bharti
What is largest rating transformer
transformers
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2.5k
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0
answers
asked
Apr 10, 2018
by
anonymous
If the back emf of a dc motor is doubled and its speed is also doubled, the torque developed in the machine...
If the back emf of a dc motor is doubled and its speed is also doubled, the torque developed in the machine will (1) get doubled (2) become 4 times (3) get halved (4) remain unaltered
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