NEMA Frame Sizes, what they mean and typical torque speed ratings by size

The NEMA frame size of motors is used for both stepper motors and brushless DC motors but it is used most commonly with stepper motors as a useful shorthand for the size of the motor (and hence the power and torque).

Always remember that (within the NEMA sizing system) the length of the motor will vary but the NEMA frame size simply refers to the diameter of the motor face.

Most commonly these faces are square (for example the ZDN2319 which is a square faced 1.9Nm NEMA 23 stepper motor) but in some cases they may be circular (as with the ZDBLM57600 brushless DC motor for example)

Frame sizes are split up into NEMA (National Electronic Manufacturers Association) ratings.

Diameter isn't everything when it comes to stepper motor power

Changing the stack length will generally not impact on the speeds that you can get but it will have a major impact on the torque (turning force) that you are able to achieve.

For example the ZD2N2318 and ZD10N2318 stepper motors are both NEMA 23 motors (therefore 57mm diameter) but the ZD2N2318 is 42mm long whereas the ZD10N2318 is 104 mm long.

The difference in torque between the 2 motors is 0.6Nm for the ZD2N2318 and 2.4Nm for the ZD10N2318. The difference in stack length of a motor with the same NEMA rating has therefore quadrupled the possible torque. The reason for this is quite simply that everything else in the motor design (bearings, distance between stator and rotor, materials etc.) has remained constant but the extra length has allowed a greater electrical power (and hence magnetic power) to get into the motor at any one time and this delivers more torque to the motor shaft.

The stepper motor controller you choose won't change the NEMA motor size of the motor but it will change the performance you get from it!

Equally the stepper motor controller that you use will have a major impact on the mechanical performance you are able to achieve using the motor. If the controller is not able to deliver more power than the motor can handle then it is unlikely that you will be able to achieve the maximum possible mechanical performance from the motor. 

One of the key reasons for this is that a certain controller may be able to deliver full power from one motor but, as the motor stack length is increased that particular motor controller may struggle to get the power into the larger motor coils to deliver the required torque. There are other reasons that can affect this. Why not have a look at our support section for more information on these factors.

As an example of this, our stepper motors with integrated controllers have higher powered controllers the bigger the motors get.

See the table below for an overview of frame sizes.

MOTOR FRAMES AND TYPICAL SPECIFICATIONS FOR STEPPER MOTORS

What next?

If your interest in motor sizes was purely academic then we hope we have helped. If you have any questions about this please do not hesitate to get in touch and we will do our best to help.

Alternatively if you are looking for a motor and aren’t sure which is best for your application then you could start by having a quick look at our standard range.

We offer a range of stepper motors of different sizes which are available in geared or standard format.

As always, if you have any questions about choosing the right motor or the pros and cons of a long stack NEMA 17 versus a short stack NEMA 23 (for example) then you can get in touch with us via online chat, phone or email.

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