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Earthing Resistance
What is Earthing Resistance?
farhan
- Jun 27th, 2013
Question:- what is earth risistance.explain the earth risistance with the diagram
sushree16
- Feb 1st, 2009
It is used to reduce the damage on an earth fault. It capture the fault current when fault occur so that the extra current will not flow in the equipment in this way equipment is protected.
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AC & DC System Components
In DC only resistive component exists where as in AC system resistive, capacitive & inductive component exists. Why its so?
Harish P. Girhe
- Jan 16th, 2011
It is because of loads reactance. Reactance either capacitive or inductive that depends on frequency. XL=2(pi)FL Where f is supply frequency. In DC supply f=0 hence XL=zero. Similarly Xc=1/2(pi)F.C=0 in dc supply. Thats why only resistance is to be present in DC system.
arjun karnati
- Jan 19th, 2009
Good question. to answer this question first of all we need to study the terms resistance, inductance, capacitance on atom level. Generally what we know is Resistance: which opposes the flow of electr...
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Synchronous Generator
How and when synchronous generator acts as a synchronous condenser?
mallick.subratkumar
- Mar 20th, 2009
When synchronous generator is over exited by connecting an induction motor parallel to it, the generator gives a leading power factor which act as asynchrous condenser, it used where most of load are pure inductive (like motor).
vishweswarrao
- Mar 11th, 2009
Whenever synchronous motor is operating under over excitation it acts as synchronous condensor. This mode of operations are used for improving power factor.
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Alternator
Why alternator is operated at lagging power factor?
How alternator responses with changing the load?sinhasunilk
- Jul 3rd, 2010
The Alternator has very little margin to run in the leading P.F. so far electrical stability of alternator is concered. If we operate generator at higher leading P.F. machine will become uns...
rajakumar1985
- Sep 9th, 2009
Since the Synchronous generator having the property of supplying the reactive power along with the real power, this can be operated in lagging power factor only. Suppose if it want to work with leadin...
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Induction Generator
Is it possible to run the induction generator only with the inductive load (without the use of capacitors for supplying the reactive power)? Explain
bittu123
- Nov 9th, 2011
I believe, You must be trying to ask "Will induction generator generate power with only inductive load??"... No, never....... Proper working of IG(Induction Generator) must need two thing 1. speed h...
anupam_srivastav
- Oct 2nd, 2009
We use capacitor in single phase induction motor to produce displacement in two winding which consequently produce rotating feild, now we can have a similar effect by using shaded pole method, but used only in small sized motor (40w
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Voltmeter Measurement
If we connect a voltmeter between earth and ground wire, how much it will measure?
bittu123
- Nov 9th, 2011
there is no difference bet earth wire and ground wire, both are same thing. BUT, if U mean earth as soil (i will refer soil as earth), and U disconnected ground wire from soil and put a voltmeter in ...
p2atik
- May 16th, 2009
Since the earth and ground wires are at same potential there will be no potential displayed in the voltmeter,But on the contrary volts?may be displayed between the?NEUTRAL and the ground/earth wire.
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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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LT Panels
What are the various types of LT panels? Name them.
Nisar shaikh
- Sep 25th, 2011
Properly Earthing and Bus bar side some Gape and properly insulation
Total load Distribution system
Power factor properly Automation system
Properly switch system -
Use of DC machine
We have enough category of AC machines more relliable than DC machine then why we are using DC machines in some application yet?
rajakumar1985
- Sep 7th, 2009
Each AC and DC machine having its own characteristics.According to the reguirement, the motors will be selected. Also the availability of supply is taken into consideration. But normally AC is preffered than DC due to its low maintenance and relaiability.
shravan.rawal
- Sep 4th, 2009
Take an eg. of DC series motor, it's properties are suitable for Railway engine, at the start it has high torque and low speed and once the core gets saturated it's torque is low but the speed is higher, so for this kind of special requirement we require DC M/C
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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.
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Capacitor Banks
What is the best method to connect two capacitor bank?
behera.tapan
- Nov 13th, 2009
It is best to connect bank in delta because if connect in star it will required three times more?capacitance as?in case?delta for same reactive power supply and finally connect both bank parallel across load or out going feeders.
buntysurat
- Nov 13th, 2009
Capacitors should be connected in star with their star point is earthed. This arrangement reduces Phase voltage to each unit by root 3 and thus the voltage withstand capability of each unit. The star ...
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3 Phase Motors
Why do 3 phase motors rotate in the opposite direction when any two phases are interchanged?
deepanshu_jadon
- Mar 10th, 2010
By the interchange of two phases Force acted in the winding inverse.if motor rotate clockwise then by the changing the two phases it start rotate in anticlockwise direction
M.Mohanraj
- Dec 8th, 2009
Magnitude is different in 3 phases so it is possible to rotate reverse direction.
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Voltage Drop
How to can calculate voltage drop in a cable?
pveee
- Dec 29th, 2011
Voltage drop in 3 phase circuits is Vd=(1.732xI(Rcos + Xsin)L)/(1000xno.of runs)
I is full load current,
R resistance of the conductor,
x resistance of the conductor,
L length of conductor in meters.
bijumenon
- Oct 25th, 2009
According to me this is how the voltage drop in a cable is calculated.If*SQRT(Rf Cos(phi) + Xf sin(phi)) / no. of runswhere....If is the full load currentRf and Xf is the resistance and reactance of the feeder. (Rf = R *L/1000; L= length of the feeder).
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Earthing Standards
What is the standard for Cable sizing & Voltage Drop?What is the standard for earthing?
maxandrean
- Jul 5th, 2010
Standart Earthing Cable in practice is :1. For the cable size is 16 mm2 , the size is equal to the line cable.2. For cable size above 16 mm2, the size is half size of the line cable, but not less than...
salman_moazzam
- Feb 2nd, 2010
Depth to which you must dig. How much should be the amount of salt and charcole to be put. Especially in earthing we must go to the depth untill you get wet mud.
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Transformers and Varying DC Current
Will DC current that varies, for example a DC square wave, but that only sinks to neutral (0V) and not enough to cause current to flow in the opposite direction, pass through a transformer? If so, how will you be able to calculate reactance for this?
ravs42
- Aug 8th, 2010
A DC square wave will have a very high value of dv/dt as compared to the pure sine wave. When it is striked to transformer, a high value of dv/dt would not be responded by it, as a result, the waves ...
Abhijit_atrangi
- Feb 22nd, 2010
No, only change in flux will induce the emf in a ckt. and that only feasible with AC that goes in opposite direction also. But in case of DC that produce flux with no change that never cause any emf in circuit. In case of DC square wave you change the magnitude of a wave from zero to max.
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Potential Transformer
What is the function of a potential transformer?
dhands
- Jun 6th, 2010
Potential transformer is used to measure the high voltage. It is nothing but stepdown transformer. In our metring systems are dsigned only for 110 v or 220 v but we are using 11000, 22000, 33000, ect. For ex PT input is 11000 v but output is 110v.
deepanshu_jadon
- Mar 10th, 2010
Potential Transformer is used to measure VoltageIt is used in protection
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Power Lines Protection
Why the 1st zone of protection relay is 90% not 100%?
ashokumarrk
- Nov 14th, 2010
Zone-1 protection is 80% in (NTPC, POWER GRID, NPCIL, NHPC, BBMB....) bcz we have consider the errors in CT, PT and also the line length. Datas provided should be same as the actual, but it wont. In order to compensate all these Zone-1 protection is 80%
pradipsabar2009
- Jul 29th, 2010
If we consider the 100%, 100% in the sense there is another CB present there. so there is a dilemma which CB should operate first. Hence the first zone of protection is never 100%
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Main Switch
What the name given for to connect the main switch supply to the various appliances?
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Voltage Levels
Why all voltage level are multiples of 11, like 220V, 440V, 1100V instead of 200V, 400V, 1000V?
pradipsabar2009
- Jul 30th, 2010
The value of form factor is 1.1 which is calculated for the sine wave. At this value of form factor, leakage flux is minimum and efficiency is maximum for any electrical machines. These machines are operated at sine waves.
dhrumil041189
- Jun 11th, 2010
Because number of disc of insulators are rated in order of 11 kV so all these are transmitted in the multiple of 11.
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