Fan load curve generation and matching with a given motor size

guest; look in the grainger catalog for your answer. pac

Friend you are almost there.The point of intersection of the motor Torque speed curve and the that of fan determine the operating point.The area between the two curves gives the accelerating torque required to be produced by the motor to bring the fan to rated speed.You need to know the GD sq of the fan and that of the motor.Now add the two and determine the acceleration time by the formula Ta=GD sq*speed/TA*375.where Ta =acceleration time

Speed=Speed in Rpm

TA =acceleration Torque obtained from the graph

375 a constant

GD sq-= sum of motor+fan GD sq.

This time should be less than the hot withstand time of motor.If not either select another motor with a higher withstand time or go in for a special motor if fan is large and acceleration times are high.The above applies if you select a cage induction motor.If you go in for a wound rotor(Also called slip Ring motor)then you can select a suitable starter to give high starting torque and manage it as most of the heat generated during acceleration will be dissipated in the resistance.For large fans in cement and power plants requiring ratings of the order of 5000Kw normally slip ring motors are used