Problem a. (i) Sketch the ideal power curve of the turbine with the following characteristics: • rated speed is 14 m/s ⚫rated power is 1.25 MW ⚫ cut-in speed is 5 m/s ⚫furling or cut-out speed is 20 m/s (ii) Given part (i), calculate the energy produced in one day if the wind blows continuously between 15 and 20 m/s all day (iii) Can the energy produced in one year be determined if you are told that the average wind speed is 14 m/s? Explain why.

5-25 Electric power is to be generated by installing a hydraulic turbine-generator at a site 110 m below the free sur- face of a large water reservoir that can supply water steadily at a rate of 900 kg/s. If the mechanical power output of the turbine is 800 kW and the electric power generation is 750 kW, determine the turbine efficiency and the combined turbine- generator efficiency of this plant. Neglect losses in the pipes.

× 4:03 K s.eng.ruh.ac.lk □ Û 8. Figure 4 shows the core of a simple dc motor. The magnetization curve for the metal in this core is given by Figure 5 and Figure 6. Assume that the cross-sectional area of each air gap is 18 cm² and that the width of each air gap is 0.05 cm. The effective diameter of the rotor core is 4 cm. L It is desired to build a machine with as great a flux density as possible while avoiding excessive saturation in the core. What would be a reasonable maximum flux density for this core? ii. What would be the total flux in the core at the flux density of part (i)? iii. The maximum possible field current for this machine is I A. Select a reasonable number of turns of wire to provide the desired flux density while not exceeding the maximum available current. Flux Density, B (T) 2.8 སྤྲ ཤཱ ཀ ཀཱ བྷ ཀ ཡཱཾ བ ་ 1.2 1.0 0.4 0.2 4-48cm Figure 4 0 10 20 30 40 50 100 → Depth 4 cm -0.05 cm 200 300 500 1000 2000 Magnetizing Intensity, H (A.turns/m) Figure 5 Magnetization curve…