# Motor Selection



## hanz (Jun 17, 2013)

Hey guys, I'm currently making a variable speed manufacturing conveyor belt for my mechanical engineering senior design project. I am lacking in my electrical skills, but I figured out the theoretical requirements needed to run the system and was hoping someone could help out with figuring out how to choose a motor/speed reducer. The requirements are as follows:

Motor Type: Brushless
Torque Range: 10.5-11.2 Nm = 94-99in.-lbs.
Motor Speed Range: 2-13 RPM
Power Range: 2.2-152.4 W = 0.0029-0.205 HP
Temp Range: 50-110 F = 10-45 C
It will be run continuously in a humid environment. There are no restrictions to size or whether it's AC or DC, but if it's AC then 120V is preferred.

I realize that motor will not have those exact specs so I was not sure how to choose it. I've tried Googling a few things and so far came up with these pointers:

1) Given a constant load (i.e. torque) the speed of a motor is solely dependent on the voltage applied to the motor.
2) Power is the product of speed and torque. The maximum power of a DC motor is produced at the operating point that is defined by operation at half the no-load speed and half the stall torque. 
3) The general rule of thumb for operation of a DC micromotor is to operate the motor at approximately 70% to 90% of its no-load speed and from 10% to 30% of its stall torque. 
4) For use with gearing, the motor should be selected for the minimum speed practical by choosing a motor with higher voltage ratings than the available voltage supply. 
5) For DC motors operated at a constant voltage, the speed and torque produced are inversely related. The higher the torque produced, the lower the speed of the motor will be.

However, I am not sure where to go from here. Hopefully someone can help!


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