A separately excited motor has fixed field voltage of V,=240V, and armature voltage V, that varied from (120 to 240V), R,=1000, Rdi varied from (1000 to 4000), A adj R=0.440, and N,=4000 turns. The magnetizing curve is given at n,=1200rpm as in the following table: E, (V) 150 200 220 260 270 280288290 I, (A) 0.350.480.560.780.87 1 1.2|1.4| 1. What is the speed, the torque and the efficiency when L=25A, Rd=1750 and V,=180V? `adj 2. Find the speed regulation. A 3. What is the maximum speed could be reached by varying both V, and Rd when1,=25A? A `adj 'A 4. What is the maximum speed when I,=50A and F.=520A.turn. AR 5. Draw the torque-speed characteristic.

The current generated by the waterwheel generator changes direction as the wheel rotates, that is, it is an alternating current.  Could you design a simple generator like this that would induce a current that continuously flowed in one direction (a DC current)?  If not, explain why not.  If so, describe and sketch your model solution below.

× 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…