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Motor Stator Length Affects...?

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dknguyen

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All things being equal, larger diameter motors provide more torque but spin more slowly. I forget what longer stator length does. THe only one I remember is that longer stator length makes motors more efficient. DOes it affect torque or RPM? I can't remember.
 

RCinFLA

Well-Known Member
Not sure what 'all else being equal' means. Type, size, diameter, rotational speed, power, air gap all are variables. Application usually sets compromises.

You have to have a certain amount of core area for a given power motor to keep flux density within capability of core material used.

Brush based, AC-DC motors usually have longer length but more due to application limiting desired diameter. (like hand drill) For a necessary hp motor, if you don't want too big a diameter then you lengthen the core. It may take some hit on efficiency over a larger diameter shorter motor but also depends on rotor gap and rotational speed.

A high rotational speed motor can have more air loading loss in a large diameter motor. In this case a longer, thinner motor may be more efficient. But maybe you want this to help cool the windings.

A small motor, like vibrator motor in mobile phone the air gap become a dominate factor. This along with application looking for thin motor drive long narrow form factor.
 
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shortbus=

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Most Helpful Member
as the "gurus" are always saying - not enough information!

AC or DC motor? brushed or brushless? inductive or synchronous?

for the most part RPM is a result of the number of poles, not the diameter.

cary
 

user_88

Member
.... I used to work for a water pump company.
The downhole water pumps came in a variety of power ratings. 1/2 hp, 1 hp, 2 hp ... maybe a little larger.
As the design motor horsepower increased, so did the length of the pump motor cylinder. However, the motor diameters were all the same.
They were sized to fit into a 4" diameter PVC pipe ... resting at various depths below the ground.

It would seem that unless there is a particular reason ... such as residing in a well bore ... the more efficient design would be to go with a larger diameter motor, as opposed to a longer cylindrical length. I guess the idea is to obtain the largest magnetic field strength/flux density ... and field intensity. .... That is, to obtain the most efficient motor design. This ought to be the larger diameter version.
 
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