A 91-cm axial-flow fan is to deliver air at 16.1m3/sec against a static pressure of 120 Pa when rotating at a speed of 1165 r/min. The fan has the following speed-load characteristic. It is proposed to drive the fan by a 12.5 kW, 230-V, 46.9-A, four-pole dc shunt motor. The motor has an armature winding with two parallel paths and Ca = 666 active conductors. The armature-circuit resistance is 0.215?. The armature flux per pole is ? d = 10-2 Wb and armature reaction effects can be neglected. No-load rotational losses (to be considered constant) are estimated to be 750 W. Determine the shaft power output and the operating speed of the motor when it is connected to the fan load and operated from a 230-V source.

Transcribed Image Text:

Speed, r/min 1200 13.9 700 3.6 800 900 1000 1100 Power, kW 6.5 10.8 4.9 8.4