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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Dear Friends, Need your help for connecting APFC panel, Quotation : I have 2 No’s 1000 KVA Transformers, both transformers are having separate APFC panels, ( Tr-1,400KVAR, TR-2,450 KVAR) Now I want to stop One transformer, present load is 650Amps, Max, So One transformer is enough, I have switched OFF TR-1, but PF is not maintaining properly, its 0.5, So now I want to connect TR-2 APFC also in TR-1 Loads, Can any one answer for my Quotation with drawing, how to connect TR-2 APFC panel in TR-1 Loads,

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