Through submarine DC cables, two countries (System A and System B) are connected together, as shown in Figure B2 (i). Each submarine cable has a dc voltage rating of 150 kV, and a resistance of 0.005 Ω/km. The primaries of the transformers at each end of the link are connected to the 200 kV ac network. Select an appropriate value for the transformer secondary line voltages, and give reasons for any choices that you make. 200 kV (line) 图 200 kV (line) System A System B ?

In the circuit in Figure 2, the capacitor connected to the a-b terminals of the transformer anda circuit consisting of resistance is defined as a load circuit. a)Find the average power spent by the load circuit? b) How much of the average power calculated in a) by the resistance in the load circuit and how muchspent by the capacitor? Comment on the results obtained?

• If the transformer has N₁=1,000 turns and N₂ = 5,000 turns. What will be the primary Power, (P₁), comparing to the secondary power (P₂)? P1 will be 5 Times lower than P2 P1 is equal to P2 P1 is 50 times lower than P2 P1 will be 5 times higher than P2

2.14 The resistances and leakage reactances of a 40-kVA 60-Hz 7.97-kV-V:240-V single-phase distribution transformer are R1 = 41.6 2 R2 = 37.2 m %3D X1, = 42.1 2 X1, = 39.8 m2 where subscript 1 denotes the 7.97-kV winding and subscript 2 denotes the 240-V winding. Each quantity is referred to its own side of the transformer. Draw the equivalent circuit referred to (i) the high- and (ii) the low-voltage sides. Label the impedances numerically. a. b. Consider the transformer to deliver its rated kVA to a load on the low-voltage side with 240 V across the load. (i) Find the high-side terminal voltage for a load power factor of 0.87 power factor lagging. (ii) Find the high-side terminal voltage for a load power factor of 0.87 power factor leading.

In the single-phase, three- winding, transformer, the primary current is equal to lo at the condition of ints there is no load on tertiary windings the current in secondary windings equal to zero the resistances (R1, R2, and R3) in transformer windings are equal the inductances (L1, L2, and L3) in transformer windings are equal.

A A-A three transformer bank, each of 10 kVA supply a total load of 20 kVA. One of the transformer become, disable and hence the circuit works on V-V open delta connection. Find for this connection. (a) (b) (c) (d) (e) kVA load carried by each transformer. % of rated load carried by each transformer. Total kVA rating of V-V open A connection. Ratio of V-V and closed A ratings. % increase in load on each of the two V-V connected transformers. M

A15 The rating of transformer is stated in terms of Ques (Write True

Problem 1 - Series en Parallel AC networks [19] Look at the circuit in Figure 1 and determine the following: (a) Total Admittance. (b) Total Impedance. (c) Total Current (l:). (d) Current (I1) through impedance Z2. (e) Current (12) through impedance Z3. (f) Current (I3) through impedance Z4. (g) Is this an inductive or capacitive circuit? A. B Zs 220V;50HZ Figure 1 (h) Voltage across Z1. (i) Voltage across A and B. G) Voltage across Zs. Z1 = 3 + j5 ohm Z2 = 10 + jo ohm Z3 = 5 + j15 ohm Z4 = 10 – j30 ohm Zs = 20 – j30 ohm Admittance and Impedance in rectangular notation. All currents and voltage in polar notation. Take voltage as reference.

2.14 The resistances and leakage reactances of a 40-kVA 60-Hz 7.97-kV-V:240-V single-phase distribution transformer are R1 = 41.6 2 R2 = 37.2 m X1, = 42.1 2 X, = 39.8 m2 where subscript 1 denotes the 7.97-kV winding and subscript 2 denotes the 240-V winding. Each quantity is referred to its own side of the transformer. a. Draw the equivalent circuit referred to (i) the high- and (ii) the low-voltage sides. Label the impedances numerically. b. Consider the transformer to deliver its rated kVA to a load on the low-voltage side with 240 V across the load. (i) Find the high-side terminal voltage for a load power factor of 0.87 power factor lagging. (ii) Find the high-side terminal voltage for a load power factor of 0.87 power factor leading. c. Consider a rated-kVA load connected at the low-voltage terminals. Assuming the load voltage to remain constant at 240 V, use MATLAB to plot the high-side terminal voltage as a function of the power-factor angle as the load power factor varies from…

A 50Hz, single phase transformer has a ratio of N2:N1 = 0.2. On full-load, the secondary current is 200A. The resistance and reactance of the primary winding are 0.8 ohm and 4 ohm respectively. The corresponding values for the secondary winding are 0.04 ohm and 0.1 ohm. If the secondary is short circuited, what voltage must be applied to the primary to produce full-load current? What will be the copper loss?