We are studying the use of a permanent magnet DC motor in a roller motion application. The motor has a voltage Vk, an armature resistance Ra, and when it turns a cylindrical roller (load) at n revolutions, it draws a current ia. The torque required by the load is proportional to the angular velocity ω with a proportionality coefficient Kφ. All losses except for ohmic are negligible. ia = 19A, Vk = 230V, n = 380, Ra = 4.5.calculate the mechanical torque delivered to the load (roller),

a) To increase the output of an ac generator, a student has the choice of doubling either the generator's magnetic field or its frequency. To maximize the increse in emf output, A - he should double the magentic field.B - he should double the frequency.C - it does not matter which one he doubles. b) Two students display their ac generators at a science fair. The generator made by Student A has a loop area of 100 cm22 rotating in a magnetic field of 20 mT at at 60 Hz. The generator made by Student B has a loop area of 75 cm22 rotating in a magnetic field of 200 mT at at 120 Hz. Calculate the emf of the two generators. Student A: Student B:

× 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…