A 130 kW, 470 V separately excited dc motor has the following rated values (nameplate): 1940...

 

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A 130 kW, 470 V separately excited dc motor has the following rated values (nameplate): 1940 rpm (full load), 2680 rpm max (no load), 300 A (full load), 0.0.0935 2 armature resistance. The maximum armature current is 1.8 times the rated value. The motor efficiency is 90 %. Armature and field windings have separate power supplies. Assume the magnetic circuit is not saturated and neglect armature reaction. Ignore all mechanical losses in the calculation of torque. The load torque has a constant component equal to 150 N.m, and a component proportional to speed, equal to 300 N.m at rated speed. 1. Motor operation – rated operating conditions, using nameplate information (a) For rated operation, compute the total losses, armature and field copper losses and speed dependent losses. Indicate the armature copper losses. (b) Compute the total input power. (c) Compute the no load speed for rated voltage and field current, and the speed regulation. (d) Compute the field current at maximum speed under full load (rated current) conditions, in % of rated field current. (e) Find the rated and the maximum shaft torque at full field, and at reduced field, as defined in Q1 (d). Neglect mechanical losses. A 130 kW, 470 V separately excited dc motor has the following rated values (nameplate): 1940 rpm (full load), 2680 rpm max (no load), 300 A (full load), 0.0.0935 2 armature resistance. The maximum armature current is 1.8 times the rated value. The motor efficiency is 90 %. Armature and field windings have separate power supplies. Assume the magnetic circuit is not saturated and neglect armature reaction. Ignore all mechanical losses in the calculation of torque. The load torque has a constant component equal to 150 N.m, and a component proportional to speed, equal to 300 N.m at rated speed. 1. Motor operation – rated operating conditions, using nameplate information (a) For rated operation, compute the total losses, armature and field copper losses and speed dependent losses. Indicate the armature copper losses. (b) Compute the total input power. (c) Compute the no load speed for rated voltage and field current, and the speed regulation. (d) Compute the field current at maximum speed under full load (rated current) conditions, in % of rated field current. (e) Find the rated and the maximum shaft torque at full field, and at reduced field, as defined in Q1 (d). Neglect mechanical losses.