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Capacitor Connection
Why the capacitors are connected in delta? What advantage it having than star connection?
bittu123
- Nov 8th, 2011
Prime reason : Delta connection will give 3 times more reactive power(kVARs) than star connection.
there are few more reason....
1. less triplen harmonic
2. less heat loss, since current is I/1.732 where I will be the current star connection pr phase
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Electrostatic Power
Is it possible to generate electrostatic power? If yes, how?
bittu123
- Nov 8th, 2011
Yes electrostatic power generation is possible as VAN DE GRAAFF generator is best example of it. But this is not economical and usable for general purpose, So, Electrostatic power generation is not pr...
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Electrical Wiring and Circuit Questions
1)How much current can a 3-1/2 core 100 mm wire carry?
2)What is the latest generation of circuit breakers called?
3)What are the special cables required for explosion proof wiring?
4)What are the different types of soft starters for large motors?
5)What is the similarity and what is the difference between relays and PLC?bittu123
- Nov 8th, 2011
I am answering few of them................. 1)How much current can a 3-1/2 core 100 mm wire carry? - It depends on "what conductor(aluminium, copper or else) you are using" and "whether it is insula...
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Contactors in circuits
Why we use contactors in ckts....how many types of contactors are there.. how we select the contactor for in ckt for its operation
bittu123
- Nov 8th, 2011
Contactor is basically a large relay kind of thing which is used to switch large amount of power. It has multiple contacts and all contacts can be switched together. all multiple contacts are controll...
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APFC Panel Circuit Fuse Units
Why We should use only Fuse units in APFC Panel circuit instead of ACB/MCCB/MCB?
bittu123
- Nov 8th, 2011
Automatic power factor correction panels will control the load power factor by sensing various available parameters like Current, Power Factor, and KVAR.... Since sensing units are already there whi...
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DC Generator Brush
Why the brush is fitted in M.N.A axis? What is its effect on speed?
bittu123
- Nov 9th, 2011
Since reversal of current take places at MNA not at GNA, So, commutation can be improved by putting brush at MNA. Otherwise it leads sparking and damaging brushes and commutator. If load connected ac...
Nishant Choudhary
- Jun 3rd, 2011
It does not effect the speed it is done to reduce sparking at the commutator contacts
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Power Supply Phase
Why do we use a single phase and a three phase power? Why dont we use two phase or four phase upward?
bittu123
- Nov 10th, 2011
Continuing my answer............... I wrote above "Differentiating single and double phase is really a big task. As single phase stand alone don't work, it always need neutral(returning path), U may ...
bittu123
- Nov 9th, 2011
As we increase the phase, output rating of machine also increases(like output rating of 3ph is 1.5 times more than 1 ph),pulsation in output decreases, this really encourage to have greater phase BU...
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CT Earthing
Why ct earthing should be connected at one end only? if ,we connect more than one end means what will happen?
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Neutral Circuit and Core Balance Circuit Protection
What is the difference between neutral circuit and core balance circuit protection?
Raman Jain
- Nov 25th, 2011
In neutral circuit protection , the CT is placed in neutral conductor and it is true earth fault protection.
on the other hand , in core balance protection the CT is placed in 3-phase cable and measured the unbalanced current in the cable. So it is protection against the unbalance between phases. -
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Electric motor start-up
Why there is a fivefold increase in a current at electric motor start-up?
eng: ahmed gharieb
- Dec 5th, 2011
Every thing in the first being hard but with time it get better. The IM is one of this thing, as in the start n=0 so that the equivalent cct of IM
exactly as before
Thanksbittu123
- Nov 8th, 2011
If You may be talking about DC motor, here is the explanation........ current through rotor is given by i=(V-E)/R. But during starting no emf is induced, E=0, So, i= (V-0)/R must be greater than if ...
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Alternator Regulation
Why most of the alternator is connected in star and have high regulation around 30% as compared to transformer?
sinuhe
- Dec 7th, 2011
There will be a large amount of third harmonics in current flowing "inside" the delta connected generator.
Raman Jain
- Dec 3rd, 2009
The cost of insulation is the deciding factor . If one is using delta connection , the insulation required will be for Ph-Ph voltage but in the case of Star connection the voltgae will be 1/1.732 times. So cost will be less.
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Touch phase wire
Can we Touch phase wire in air when we r not touch ground what happens
amolgaonkar
- Dec 9th, 2011
When you touch the phase wire in air the current will enter your body but it will have no way to escape or complete the circuit thats why you will not feel the shock...the best example is you might ha...
Tarun Aggarwal Ymca
- Jul 22nd, 2011
only high potential cannot cause flow of current. So, when a Human being touch such a wire, its whole body is at a high potential, but due to the absence of a lower potential, the current cannot flow....
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What is welding transformer ?
Why we use it in welding and what is the difference in welding and ordinary transformer?
Srinivas
- Dec 20th, 2011
Welding transformer is used for welding purpose, these are the special type of Transformer. which will be having only few turns on secondary side of the transformer winding. it will operate at low voltage in the range of 60 to 110 v Ac where as current will be very high upto several thousand amps.
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Synchronous Motor Vs Induction Motors Speed
Synchronous motor rotates with constant speed but induction motor is not like that, Why?
What is the construction difference between Synchronous motor and Induction Motor?pveee
- Dec 26th, 2011
Synchronous motor are constant speed motors where IM are variable speed motors.
Synchronous motor requires special starting set up where as IM are self stared. -
What is the resistance between neutral and earth.
RAJA.P
- Dec 29th, 2011
The difference between the earth and neutral is 0.8 or below 1
bittu123
- Nov 8th, 2011
If neutral is grounded, resistance bet earth and neutral will be ideally 0 (zero). or very low depends what conductor is used to connect neutral with earth.
If neutral is not grounded, resistance will depend on atmospheric condition and air density, will be very high, tends to infinity -
Transformer Capacity
If the capacity of a Transformer is 20/26 then what does 20/26 shows? what is its purpose?
pveee
- Dec 29th, 2011
If 20/26 is in kva 20kva indicates capacity of transformer under ONAN cooling.
If the capacity is 26kva it is provided with ONAF cooling.
If 20/26 is voltage 20 indicate primary side voltage, 26 indicates secondary voltage, it is stepup transformer. -
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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Electrical Engineering Interview Questions
Ans