Answer / sagarika dash

An integrated course in Electrical Engineering J.B.GUPTA

what is the reason for choosing DYn11 in transformer, why not DYn12 or something else

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1. A 380 / 220 V r.m.s. 3-phase 4-wire circuit carries loads of 8 + j8.1 ohm; 4 + j4.1 ohm; and 2 +j2.1 ohmin the three phases respectively. The length of the circuit is 100 m, and the resistivity of the phase conductors is 0.0005 Ω/m. The neutral conductor is of the same size as the phase conductors. a) Select a reference angle 0for the first phase. Then write down the three phase voltages in both polar format and complex number format. b) Make appropriate assumptions, and take temperature effects on resistance is insignificant. Calculate the currents in the three phases. (Note: Determine conductor resistance, and apply Kirchhoff’s Voltage Law) Based on the result, suggest a main switch rating for the circuit. c) Show your preferred direction of neutral current in a diagram, and then determine its value. (Note: Apply superposition principle, and Kirchhoff’s Current Law) Use its magnitude to show that in this circuit, the unbalanced load may increase the voltage drop in some of the phases. (Note: Also observe the common volt drip in neutral) State your assumptions, if there are any. d) Suddenly the neutral wire of the circuit is broken. Estimate the new currents in the first phase, i.e. Phase L1. State your assumptions, if there are any.

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On what basis no of earth pits are to be decided either for transformers or for equipment?

8 Answers   BEL, Reliance,

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1. Why is the speed of shunt motor practically constant? 2. Why dc series motor use to start with heavy loads? 3. advantages & disadvantages of separately excited generator over self excited generator?

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Is it possible to use AC supply insted of DC supply in trip coil operation? if not, why?

5 Answers   HAL,

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Why the transformers are rated in KVA ? in new view

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WHAT IS THE USE OF PIG TAIL IN WINDOW TYPE CT ?

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What is NUMBER OF RUN for power cable means?

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I'm looking for a softcopy manual set for a Credence ASL- 3000. Anyone know where I can get it?

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how a.c. genarator control power factor when its conected to grid supply by incrising or decresing excitation voltage.

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I am getting differential earth fault in my transformer realy , i have checked all its CT & control wiring but do not get fault, Please help

6 Answers  

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hello if any one have papers vof hpcl or sail, plz send me

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