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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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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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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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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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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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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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Pure Sine Wave Inverter
What are the applications of pure sine wave inverter?
engineerfaisal
- Apr 13th, 2009
Pure Sine Wave Inverters will: Allow inductive loads like microwave oven and motor driven products to run faster, quieter and cooler. Reduce or eliminate audible and electrical noise in fans, flo...
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Three Phase Induction Motors
Why capacitors are not used in 3 phase induction motors?
mohann2008
- Apr 11th, 2009
In three phase induction motors, capacitors are not needed, because when the current passes through? three wires, three magnetic fields will be produced. Due to the interaction between those magnetic fields, RMF will be produced automatically without the help of capacitors.
naresh20047038
- Mar 20th, 2009
In 3 phase Induction motors rotating magnetic field will be created which in turn interacts with the rotor conductors resulting in rotation of rotor, so there is no need of capacitors for starting pur...
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APFC/Capacitors in DC circuit
Why many people do not connect the APFC/Capacitors in DC circuit?
KKMSURESH
- Apr 8th, 2009
APFC means Automatic Power Factor Controller. Power Factor is applicable only in an AC Supply, DC is one of direct current, there is no Power Factor in DC Supply.
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Phase Shifting
Why do we use phase shifting at Current Transformer?
raul10
- Apr 8th, 2009
We use phase shifting in current transformer to transfer the magnetic flux density around the core
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Current Circulation
Is it possible if their is no voltage then their is no current circulation or does it depend on circuit condition?
manojprabu
- Apr 4th, 2009
You are right without voltage their is no current circulation in any circuit (EMF is electro motivate forces is the force that produces movement of electrons in circuit if it is closed)Voltage is the major source of current.
arun uday rana
- Aug 2nd, 2008
Current is nothing but flow of charge inside the conductor. It is always true that any fluid or gas always flow from higher pressure to lower pressure (or temp.). It is same in the case of charged p...
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Power Factor
Why the Voltage rises when Leading Power Factor is occurs?
shobhit bansal
- Apr 3rd, 2009
When there is a case of leading power factor, that means synchronous generator works in over excitation mode, reactive power will be generated, and as we know that change in voltage is directly prop...
SURAJTHEGREAT
- Mar 18th, 2009
We know flux is 90 degree ahead of voltage...If leading p.f. load is connected,the armature flux and main flux aid each other,Bcoz current(field current=flux)is 90 degree ahead of voltage. (Thus 2 fluxes aid each other)and since voltage propotional to flux,voltage increases..
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Sub-Station Label
Why the Substaions are labled as 11KV/33KV or 66/11KV etc instead of label with the POWER TRANSFORMERS Rating (In MVA/KVA)?
kannanvellai
- Mar 31st, 2009
All electrical equipments operated depend on voltage.In substations we can get same ratio transformers with various power ratings.Ex:400/200KV with 800MVA 315 MVAPower rat...
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Lightening Arrestor
Location of lighting arrestor should be near transformer or not? Why?
mallick.subratkumar
- Mar 30th, 2009
Yes it must be near to the transformer,because when there is a lightening occurs the total power must go through Lightening Arrestor to ground with out damaging the transformer.
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Conductor Size of Fuse and Cable
For 63A load we can use 25/35sqmm cable. For same rating fuse conductor size is too low. How is it possible?(Its not depends on meterial, because single strand for above cable size is enough for fuse)
haveasafeday
- Mar 24th, 2009
Generally Fuse is used for short circuit protection. That means it should be higher(normally 2 to 3 times of rated current depending on design) than other installation in a perticular circuit.
sindhejs
- Feb 16th, 2009
As we know that fuse use for the safety purpose. And current will flow on the bases of resistance, as fuse?wire of small length (so it has lesser resistance), it can withstand 63A (as 25/35sq. mm cab...
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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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BusBar
What is a busbar?
manojprabu
- Mar 22nd, 2009
Busbar is nothing but just a cable in which two or more alternator or transformer are connected after synchronising them as single cable foe connecting to load
Nwannaa
- Jan 22nd, 2009
A busbar is the metal bars of copper or alluminum depending on design that are installed in panels. The bars are dimensioned according to stipulated current carring capacity and installation type.The ...
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Wattmeter
Wattmeter has two coils in it-the current coil & pressure coil, why is the pressure coil so named? How is the power being measured by the Wattmeter?
mallick.subratkumar
- Mar 21st, 2009
Current coil means it measure current of circuit & pressure coil means it measure voltage, when current coil is connected series, pressure coil connected parallel in one circuit ,as P=V*I*cos?,
So we have V, I, & ?=[1/tan(V/I)],
Now the power is being measured. -
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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Tripper Drops
Consider you have a tripper at your house. The instant you switch on your motor, the tripper drops. What could be the problem?
mallick.subratkumar
- Mar 20th, 2009
The tripper drops because the motor is an pure inductive load & when we switch ON it, as the properties of inductive load define it oppose sudden change in current so the tripper drops when motor switch is ON.
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