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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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Circuit Breaker
Which Circuit Breaker is better either Air CB or Vacuum CB? Why?
rajakumar1985
- Sep 7th, 2009
The vacuum C.B is better than A.B C.B for medium voltage because of its better operation and longer life. But in high voltages we cant use the vacuum C.B.
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Induction Motor
Why star point of star connected motor is not grounded?
rajakumar1985
- Sep 10th, 2009
Normally the 3 phase induction motors are not star connected. In the star connected machine, the phase voltage will be 1/ 3 times. So that the torque of the machine will be reduced. Because of this reason normally all the induction motors are having delta connected field windings.
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Alternator Operation
If we put field winding on stator and armature winding on rotor then how will it operate? Will it rotate at synchronous speed or not? (Assuming that the alternator is feasible)
nikhilsharma2009
- Sep 15th, 2009
Yes, It would surely operate and run at synchronous speed. But it would be uneconomical because we should have 3 slip rings of very high current handling capacity and because of this efficiency will decrease and we will require to have high level of insulation and cooling also.
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Transformer Sound
Why do you get a typical sound when the transformer is put into operation?
nikhilsharma2009
- Sep 15th, 2009
Transformer noise is caused by the phenomenon magnetostriction. When a piece of any magnetic sheet is placed in the magnetic field it gets magnetised and elongate. But when the magnetic field is remov...
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Wattage related to Frequency
A motor rated 230V, 50HZ taking 100KW no load amps, what happen if just frequency goes to 60Hz?
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Floting Earth
What is meant by Floting Earth? What will happen if we use regular earthing instead of floting earth and Where do we have to use only floting earth.
sn_rangari23
- Sep 28th, 2009
Floating Earth used in High Voltage equipment for high voltage Pit-Earth Test carried out for Transformer, Generator, Compressor, cables etc. for checking the condition?of moister & dryness of the cable.?
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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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How to Simulate an Induction motor?
jatin patel
- Oct 16th, 2007
Transformer with secondary shorted is simulation of sq. cage induction motor
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Motor Frequency
Motor manipulator detail is 230v 50hz frequency. If you increase frequency what will happen?Is there any need for coil protection?
vijay5586
- Oct 19th, 2009
Speed N=120f/p so if we increase the frequency the seed will also increase as per our electrical stands in India we are maintaining 50Hz as the constant frequency it is better maintaining the freq...
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What is the voltage drop for 100kw motor if the length of the cable is 200m and what is the cable size.
soumendasbiswas
- Oct 21st, 2009
1.The (0.48) is it resistivity of conductor ? or any other value Well here 0.48 is the estimated voltage drop in XLPE cable.(You can get this value from any cable manufacture catalogue)2.You hav...
mustafa_musvi
- Oct 20th, 2009
Mr Biswas please specify Below is the case you mentioned regarding cable losses I have 2 questions request for your answer1 The (0.48) is it resistivity of conductor ? or any other value 2 You hav...
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Direct Current for Transformer
What happens when a transformer is supplied with direct current?
pmazulfi
- Oct 22nd, 2009
If DC supply is given to transformer there will be no change in the flux with time so there is no emf induced in the primary and secondary windings and hence transformer action will not take place.
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Calculate Voltage Drop
How to calculate voltage drop in cables?
buntysurat
- Oct 23rd, 2009
Each Cable is specified with their R & X values per Km or Mtrs. For calculating Voltage Drop across cable the effective impedance Z must be calculated for given length of cable as Z = Square Root ...
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Reactive Power Relation with Alternator
How reactive power is related to alternator? Wheather it is generated or consumed? Explain
bittu123
- Nov 9th, 2011
If alternator is Overexcited, it will deliver reactive power with lagging current while in Underexcited, it absorb reactive power with leading curreent But, it always(under or over-excited) deliver ...
buntysurat
- Oct 23rd, 2009
An Inductive Load say Induction Motor connected to an Alternator requires Active (KW) & Reactive Power (KVAr) both. This Motor receives Apparent Power (KVA --> KW + KVAr) from th...
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Power Factor
What is Power Factor? How it is calculated?
venkey_048
- Oct 29th, 2009
Power factor is the ratio between Real power to the Apparent power. It indicates, how much power was actually utilised by the present system. For example, if any system had a power factor of 0.8 mea...
Ravindra2008
- Oct 20th, 2008
In A.C. ckt their is some difference in vtg & current that angle is called as phase angle,the cosine of that angle is called as power factor. It is the ratio of resistance to impedance.
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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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Electrical Engineering Interview Questions
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