Question

Q5.8：The specifications of machine

5.8. For the machine in the previous question, calculate (a) its no-load speed (b)its rated efficiency-olcoxL-n/nN (c) the following when the speed is zero (stall condition) (i)induced voltage (ii) nput current (ii) output torque (iv) ut power (v)output power (vi) efficiency (d) he speed (in rpm) when the torque is 0.2 Nm 5 A DC machine has a no-load speed of 10,000 rpm and a rated speed of 8,000 rpm when operating with its rated supply voltage of 20 V. It has a resistance of 0.52. (a) Calculate the input current and output torque when the machine is at zero speed. (b) Calculate the input current and output torque when the machine is at rated speed (c) Sketch the machine voltage-current and torque-speed characteristics on the template provided. Label the no-load, full-load and stall operating points on both graphs and indicate the corresponding induced voltage, current, torque and speed on the appropriate axes. By observation from the graphs (without doing any calculations), what is the current and speed corresponding to operation at half rated torque? (d) 5.12. Consider the machine in the previous question. On the axes provided sketch the torque versus speed characteristies when operating at rated supply voltage and half rated supply voltage. For both curves show the values of the stall current and torque, and the no-load induced voltage and speed A DC machine has a back-emf constant of 0.24 V/(rad/s) and a resistance of 0.5 ohms. It is operating from a 12V DC power supply. At its rated speed of 400 rpm, calculate its rated hack-emf voltage (that is the hack-emf at rated sneed

Answer 1