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Current Transformer Protection Class
What is the 5p 10 , burden in current transformer?
sanjay.patel
- Nov 28th, 2008
It means CT have minimum inaccuracy is 5% when it experiences 10 time of it's rated current.5 is minimum% inaccuracyP mean Protection Class10 How much time of rated currentis Rated current
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Capacitor Banks on DG
Why many people not connect the APFC/Capacitors in DG circuit?
shrinirmal
- May 1st, 2009
When normal supply is 'On' that time APFC will be on, At that time it will consume current, for correcting P.F, in case of D.G will not run continously so avoid over load on D.G APFC panel not connected.
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Lightening
Does lightening contain voltage or current, Explain.
shrinirmal
- May 1st, 2009
An electrical discharge between cloud and earth, between the charge centre of the same cloud is known as LIGHTENING,A direct or indirect lightening stroke on a transmission line produces steep-fronted voltage wave on line, the voltage of this wave may be rise?from zero to peak value.
gdhana2006
- Apr 25th, 2009
You just imagine a heavy source accumulated in the form of clouds at the sky. You just think the very nearest contact point of earth potential to the cloud. Eg Tower, Lighting arrester etc. Once ...
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Save Power
Suppose the electricity board gives 11 kw, but the machine requires only 8 kw in such case how can we save the excess power?
bittu123
- Nov 9th, 2011
Guys, Do u really think electricity board give us power in kw??? No, We demands power as our requirement. This assumption is wrong of giving power. Suppose, In your house, 1 bulb is switched ON, so U...
rajakumar1985
- May 15th, 2009
Even the supply is capable of deliver more power than the required power, the machine will take howmuch power that needed.
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Short Circuit Calculation
How short circuit calculation done at secondary side of transformer?
yasheen
- May 25th, 2009
The low voltage side is short circuited with measuring instruments(Ammeter and wattmeter) in HV side. Now the input voltage is increased to read rated current in LV side. Corresponding HV side reading is noted
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Concrete Transformer Frame
What are the problems that may occur if a transformer frame is made of concrete instead of metal?
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CT connection for T/F differential protection
Why CTs are connected in star on T/F delta connected winding side & in delta on T/F star connected winding side for T/F differential protection?
bejoyengineer
- Mar 1st, 2009
The differential relay will not activate when we energize the transformer as the relay will activate only if there is a difference in the flow of current and that to if it exceeds the setting values.
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VFD Input Frequency
Can VFD step up to 60 Hz if it is designed to receive 50 Hz input?
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Motor Starting
The single phase induction motor starts with two phases(Using capacitor). Why can't the three phase induction motor starts with two phase?
jeet29
- Jun 8th, 2009
For the starting of a single phase motor we need two different fields and the resultant of both the fields works as the operating field revolving the motor in the direction of strong field (for more...
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60Hz Transformer
What would happen if a transformer is made to operate at 60Hz instead of 50Hz ?
expertnayak
- Jun 8th, 2009
In transformer eddy current lossesPe=Kv^2 it is not dependent on frequency so only hyteresis losses will get affectedPh=KfB^x
jeet29
- Jun 8th, 2009
If we are connecting a 50 hz transformer to a 60 hz transformer then there?hystersis and eddy current both losses increases considerably (for detail check effect of frequency on transformer losses).
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Power Factor
What is the power factor?
bashir varsi
- Jun 14th, 2009
Power factor is the ratio of active power to apperant power. for better energy efficiency it should be unity.
jeet29
- Jun 8th, 2009
Power Factor means that what amount of the power the circuit is using. If the power factor is .807 that means circuit is using 80.7% of power and the remaining 19.3% is returning back to supplying source.
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Voltage Standing Wave Ratio
List the basic ways of determining the voltage standing wave ratio in a transmission line.
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Voltage Standing Wave Ratio
List the basic ways of determining the voltage standing wave ratio in a transmission line.
naveed_ahmed
- Jul 13th, 2009
VSWR is a ratio of? Vmax to Vmin or Imax by?Imin?which can be theoretically?determined by using smith chart or practically determined by using vswr meter.
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Measure DC Current
How can we measure the DC current directly?
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Does HVDC mode of transmission has an economic advantage over EHV-AC transmission. Justify
sainathdi
- Aug 16th, 2009
HVDC- High Voltage DC Transmission system ,from the name itself we can say that its a dc transmission system and a dc transmission has two conductors one phase and other neutral. phase conductor is us...
venky_sastra
- Dec 28th, 2008
HVDC means high voltage DC transmission. Usually when we speak in common terms power p=I*I*R therefore p is propotional to I*I, A high voltage will generally involve low current so as a result the power losses are less. So it has an economic advantage over EHV-AC transmission.
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Circuit Breaker
What is single and 2 pole circuit breaker?
OLIELCTRICAL
- Aug 18th, 2009
Single pole only connect in phase incoming and out going line the load. Single pole holes top one & bottom one. max rating - 25 amps. Two pole?connect in phase & neutral. 2 holes top two & bottom two. max rating - 32. example mcb.
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Insulation resistance for of generator
What is the value of insulation resistance between Neutral and earth of a 65 KVA Generator?
csbalu
- Aug 29th, 2009
First of all let me clarify this,Insulation value does not depend on KVA rating of the Generator.It depends only on the rated voltage of the Generator.The insulation resistance is measured between the...
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When there is a sudden loss in the demand what happens to the transformer and generation?
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csbalu- Member Since Aug-2009 | Aug 29th, 2009
When there is a sudden loss of load, The Generator terminal voltage increases due to the fact that the IX drop in the generator winding decreases. The EMF generated being the same the reduced reactance loss leads to a sudden rise in generator voltage..but the AVR (Automatic Voltage Regulator) will act instantly to bring this voltage to the set value by reducing the excitation.
There is practically no effect of this on the transformer barring the reduction in I2R (copper Losses) and reduced IX drop.csbalu
- Aug 29th, 2009
When there is a sudden loss of load, The Generator terminal voltage increases due to the fact that the IX drop in the generator winding decreases. The EMF generated being the same the reduced reactanc...
spcspc1654
- Jul 19th, 2009
When there is a sudden loss in the demand then there is over-excitation of the generation and the power factor is increased. Also the rotor angle of generator is changed (unstable) for a while.
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Rated Voltage and Frequencey
Why OC test is carried out at rated voltage and frequency?
rajakumar1985
- Aug 10th, 2009
Normally the OC test is done to find out the losses. The losses depends on the voltage and frequency applied to the machine. So that while testing, the rated voltage and frequency are applied to the machine.
Electrical Engineering Interview Questions
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