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#1 newbie

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Posted 10 July 2008 - 08:13 AM

I really need ur help to answer this question....


3. Reading of an 11kV 3 phase system at 100/5 CT secondary is 3A. If current is leading voltage by 30 degree, is power consumed or generated? How much?



4. Why neutral current is not zero in 3 phase 4 wire system?



5. Why does a test pen light up?



6. Will an unlighted flourescent lamp consume power if switched on?



7. Can 3 single phase generators be used to make 1 three phase generator?



#2 subrao

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Posted 17 July 2008 - 12:19 PM

QUOTE (newbie @ Jul 10 2008, 08:13 AM) <{POST_SNAPBACK}>
I really need ur help to answer this question....


3. Reading of an 11kV 3 phase system at 100/5 CT secondary is 3A. If current is leading voltage by 30 degree, is power consumed or generated? How much?



4. Why neutral current is not zero in 3 phase 4 wire system?



5. Why does a test pen light up?



6. Will an unlighted flourescent lamp consume power if switched on?



7. Can 3 single phase generators be used to make 1 three phase generator?



#3 subrao

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Posted 17 July 2008 - 12:37 PM

Let me attempt your queries to best of my knowledge.
3.If the current is leading, it means the system is receiving reactive power.It does not indicate whether active power is received or delivered. It is indicated by direction of power flow. It simply means if kw meter is showing power or having a reverse kick when it is connected correctly.
4. Neutral current will not be zero if individual phase currents or not balanced.
5. A test pen lights up because of flow of current between line and ground.
6. It hardly consumes any power.
7. Theoretically yes but almost not possible to achieve practically
To have 3phase system the three voltages to be equal, easily achieved.
It is also necessary to keep phase angle between each phase at 120 degrees. This can be attempted by staring each single phase generator at different instants to keep required relative rotor positions which is practically may not be possible.







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