A 10-hp 120-V 1000 r/min shunt dc motor has a full-load armature current of 70 A when operating at rated conditions. The armature resistance of the motor is RA = 0.12 W, and the field resistance RF is 40
W. The adjustable resistance in the field circuit may be varied over the range from 0 to 200 W and is currently set to 100 W. Armature reaction may be ignored in this machine. The magnetization curve for this motor, taken at a speed of 1000 r/min, is given in tabular form below:
![2227_f657b699-1328-4b9f-b6d2-5eaab52fffc3.png](https://secure.tutorsglobe.com/CMSImages/2227_f657b699-1328-4b9f-b6d2-5eaab52fffc3.png)
a) What is the speed of this motor when it is running at the rated conditions specified above?
(b) The output power from the motor is 10 hp at rated conditions. What is the output torque of the motor?
(c) What are the copper losses and rotational losses in the motor at full load (ignore stray losses)?
(d) What is the efficiency of the motor at full load?
(e) If the motor is now unloaded with no changes in terminal voltage or , what is the no-load speed of the motor? Radj
(f) Suppose that the motor is running at the no-load conditions described in part (e). What would happen to the motor if its field circuit were to open? Ignoring armature reaction, what would the final steady-state speed of the motor be under those conditions?
(g) What range of no-load speeds is possible in this motor, given the range of field resistance adjustments available with