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3 Phase
Why there is 220v in 1-phase but 440v in 3-phase?
rajakumar1985
- Aug 13th, 2009
The output of generator having 120 degree phaseshift. Ever time the instantaneous magntiude will be root 3 times the phase voltage. The magnitude will be same. While measuring we are considering the two phases which is maximum.
muralykrishna
- Jun 2nd, 2009
The Phase voltage of an generator is 220 - 230 V but the Phase to phase voltage (Line Voltage) will be 400 V. Voltage of R - Phase-230 Y - Phase-230 B - Phase-230 but RY-400V BY-400V ...
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Power Consumed
If v=220V, I=25A, power factor=0.8, frequency=400Hz. If the motor runs for 3 hours, What is the power consumed?
bittu123
- Nov 10th, 2011
Calculating power, frequency and time is not required. P=V*I*Cos0 =220*25*0.8 =4400 watts answer But if you are looking for "How much energy motor consumed?" then you need time Energy consumed ...
dineshkumarsah.mj
- Jun 15th, 2011
Here Freq was given was wrong P V*I*CosAA is power factor V is VoltageI is Current P 220*25*0.8P 4400wattsPower P is 4.4Kwatts for one hour.For 3 hrs 4.4KW*3 = 13.2KW
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What is a Transducer?
BALLU_89
- Feb 21st, 2011
Transducer is a device which converts physical quantity into electrical quantity. As-Thermocouple (convert temperature into electrical volt or current) If it is correct then confirm me.
GeeK_Percy
- Oct 4th, 2009
Transducer is a device which converts any quantity into electrical siganls via mech displacement.
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Earth has the constant potential so we take it as reference.but in steo & touch voltage we use to calculate voltage of ground in 30 inch. How it is possible if no current can flow through ground?
Rahulshelke
- Jul 12th, 2010
During fault to have shortest resistance path is ground. Hence current flows through ground. hence we take 30inch during calculation.Voltage difference is created and current flows.
zakeer
- Aug 30th, 2007
We are taking earth as reference it means it's?potential is not absolutely "ZERO" but approximatelly it is zero .and the potential is not equal allover the earth it varies from place to place so we measure at 30 m in to earth
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Why Transistors are not used as switching devices?
Dr. Raman
- Jul 28th, 2006
This is not a correct question. If an interviewer asks you, you should ask in return what kind of transistor are you talking about? Is it MOSFET, BJT, THYRISTOR etc. All semiconductor transistors are used as switching devices depending upon the application.
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How do you detect the exact location of a cable fault if its cable puncture
suresharon
- Dec 27th, 2008
If it is a buried HT cable, you can avail the use of HT Cable fault locator which inject hi volt pulse into the cable and a person with an instrument can identify the exact location of the cable joint...
ramesh
- Jul 26th, 2007
You can find the fault by using murray loop test or wheatstone bridge test.
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Measure Earth Resistance
How earth resistance is measured? What should be its value?
soulzangel
- Oct 4th, 2010
Earth resisitance can be measured using megger or earth tester and thr resisitance of proper earthing must always be less than 10 ohms and for sensitive installations such as very sensitive communication and computer systems about 2 ohms is recommended.
veerateja
- Jul 9th, 2010
Earth resistance is measured by means of earth tester or megger. The earth resistance must and should be less than 0 to 5 ohms. If it is above the 5 ohms we say earth resistance is not good.
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Change in Frequency
Why do we maintain 50hz frequency? What happens when we change this frequency to any other value?
maxandrean
- Jul 5th, 2010
AC Electrical Network need to have a syncron phase for them to work. Any differences in term of frequency will shift out this syncronisation and lead the whole system to fail.
sankar_jkpm
- Feb 3rd, 2010
In our India, all the electrical power generation is based on 50 Hz. (50 cycles per second) with respect to the production of flux in alternator. So the electrical utility products are designed f...
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Current Transformer
Explain why the secondary terminal of current transformer should not be lift open circuited.
ravs42
- Aug 21st, 2010
Due to high ratio,if the secondary is left open a very large voltage will be developed at the secondary.As a result the core vl be saturated n operator working nearby vl face severe accidents.
deepanshu_jadon
- Mar 10th, 2010
In CT secondary side is not open because it has large voltage difference
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What is meaning by the SKIN effect in electrical circuits
veerateja
- Jun 2nd, 2011
In ac electrical circuits due to varying magnetic fields they induce eddy inside the center of conductor .Due to the induced eddy currents they restrict the current flow on the center and pushes the c...
ravs42
- Aug 8th, 2010
When alternating current flows thru the conductor, magnetic field intensity in the inner side is more, as a result flux concentrated on the inner conductor is very high. Since inductance of the coil i...
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What are the technical reasons for soaking transformers for various times before allowing them to pick load after a fault or maintenance outage or as a new installation.
niceashwin79
- Dec 21st, 2010
I believe it is not soaked in water but is soaked in oil.It kept for some time because to remove all moisture and air if any trapped in insulating material and windings.
SAMIR K CHATTERJE
- Nov 17th, 2007
To improve IR value of the transformer so that it would have higher dielectric strength indeed.
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In a synchronous motor armature current flows due to revolving flux which in turn rotates the load,but in no load condition armature current is zero hence thr is no revolving flux then how motor rotates? pls give books referance.
saginala13
- Jun 19th, 2010
Synchronous motor: we will give dc supply to the armature as a excitation, which causes revolving flux, so that motor will rotate at synchronous speed.if there is no excitation and the armature coils ...
GeeK_Percy
- Oct 4th, 2009
Armature winding is 3 phase winding and is supplied with 3 phase supplyField is supplied with DC supplied First motor is run at syn speed to lock rotor in syn speed now load is applied Questioner is confused actually the rotating field is produced by armature not by field.
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At what condition a synchronous motor acts as a synchronous condenser?
arun uday rana
- Aug 8th, 2008
A synchronous motor act as a synch. Condenser when the its field winding is overexcited and there is no load attached with it. The basic application of this phenomenon can be seen in the hydro power p...
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Power Factor
What do you mean power factor?What is the use of Power Factor?
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rahulr30- Member Since May-2008 | May 30th, 2008
Power factor is the ratio of Active ppwer to apparent power in sysytem,It is an index to see how much of the energy is actually being utilized to do useful work
veerateja
- Jun 11th, 2011
pf is the co-sine of phase angle b/w voltage and current.Generalley it is leading or lagging depanding on the load whether it is inductive(lag) or capactive(lead).Take voltage as reference the current...
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On what basis is the power rating of the generator decided??
bittu123
- Nov 9th, 2011
The core criteria for deciding rating of machine is LOSSES. while this may ultimately justify all the reason specified by above person. Because temperature rise of machine depend on losses. Insulatio...
raviiisc
- Jun 9th, 2011
For any electrical equipment the power rating is decided by the thermal rating.orThe temperature withstanding capability of the machine.For generator the power rating depends on temperature, volume of rotor.
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How torque is developed in motor ?
raviiisc
- Jun 9th, 2011
It is due to the interaction of one flux and one current.For example in Motor (induction motor 3-phase), the stator flux interacts with the rotor current leads to torque development.Somebody also says...
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Large Size Synchronous Machines
Why almost all large size synchronous machines are constructed with rotating field system type?
Rhombus
- Jun 11th, 2011
All the large size synchronous machines have rotating field winding because in the other case where armature is rotating we require four slip rings.. but in case of rotating field we can do with only..2 slip rings..!! :):)
veerateja
- Jul 11th, 2010
Large size synchronous machines or Alternators have rotating field winding on rotor for many reasons of them the important reasons are:- 1. The rotor can rotate at very high speeds. 2. The voltage reg...
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What should be power angle for 11KV AC generation ?
For 600 MW Generation Purpose.
raviiisc
- Jun 9th, 2011
It will be 30 to 45 degrees.We wont allow the generator to operate at its maximum power transfer such as 90 degrees.At this the reactive power supplied by generator is the leading reactivepower. But w...
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Power Generation
What measures will take for cost saving in utility and power generation
bittu123
- Nov 9th, 2011
POWER GENERATION 1. Try to increase "Diversity factor" as much as u can. 2. Try to increase "Load factor" 3. Try to decrease "Maximum demand" UTILITY : 1. Use Power factor improvement instrument lik...
Nishant Choudhary
- Jun 3rd, 2011
The first thing always be remembered that for economical purpose the power factor should always be kept around unity or close to unity this u can do by avoiding light loads or by using APFC panels to improve power factor
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Explain how direct current is produced in single-loop d.c. generator?
Nishant Choudhary
- Jun 3rd, 2011
The current produced in the armature is ac current but the commutator segment and the brushes acts as mechanical rectifier which converts ac voltage to dc voltage
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