A14,92kw , 400 v , 400 r. p.m . dc shunt motor draws a current of 40a when running at full-load. the moment of inertia of the roating system is 7,5kg-m^2. if the starting current is 1.2 times full load current. calculate a) full-load torque. b) the time required for the motor to attain the reted speed against full-load.

First we determine the motor's efficiency - a ratio of the mechanical output power and the electrical input power:

The output mechanical power is directly proportional to torque and angular speed. From this relationship we can isolate the torque:

whereby the last expression uses the angular speed in rpm units.

(a) we calculate the torque, given that the motor draws 1.2 times the rated current, i.e., 48 Amps:

(b) use formula for the acceleration time:

The startup time will be 0.74s

i'm just gonna leave this comment here, so i can get a challange done-

explanation: