Question

A 255 V, DC lathe machine, (not a 2 pole machine) has armature resistance and series resistance are 0.15Ω and 170Ω respectively. The motor has 25mWb flux per pole. The ratio of pole to parallel paths is unity. The product of this ratio and number of turns in armature section is 1000. When it runs light, it has a speed of 1200 rpm. If it runs at maximum load, it takes a current of 70A.
(1) Which machine is this one, shunt or series ? (2) Is machine lap wound or wave wound? (3) Calculate the no load back EMF. (4) Calculate the no load armature current. (5) Calculate the no load shunt current. (6) Calculate the current drawn by the machine. (7) Calculate the variable losses on load. (8) Calculate the armature power when it runs light. (9) Calculate the stray losses when it runs light. (10) Calculate the full load armature current. (11) Calculate the full load back EMF. (12) Calculate the Variable losses on maximum possible load. (13) Calculate the armature power on maximum load. (14) Calculate the constant losses at maximum load. (15) Calculate the hp rating of the machine. (16) Calculate the full load speed of the machine. (17) Calculate the armature torque on maximum load. (18) Is the full load speed the maximum speed of the motor? (19) Calculate the efficiency at maximum possible load. (20) Is machine operating at maximum efficiency when runs on full load? If not, describe it with supporting evidence?

Answer 1

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North pole is the answer.

Answer 2

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North pole