NEMA stepper motor sizes chart and selection guide

 

When selecting a stepper motor, you may encounter the term “NEMA size.” A NEMA size refers only to mounting dimensions and not motor performance. It does not define torque or electrical characteristics, so you cannot choose a motor based on the NEMA size alone. This article explains NEMA size definitions, provides a NEMA stepper motor chart and highlights other critical factors for selecting the right stepper motor.

What is NEMA?

NEMA (National Electrical Manufacturers Association) is a U.S. standards organization. For stepper motors, specifications are defined in NEMA ICS 16-2001, which standardizes flange dimensions, mounting hole positions, etc. This ensures mechanical compatibility across different manufacturers.

NEMA size specifies physical mounting dimensions only, not performance

Designations such as NEMA 17 or NEMA 23 correspond to the approximate width and height of the square mounting flange in inches. For example:

NEMA ICS 16-2001 primarily defines the following dimensions:

The NEMA sizes only specify physical dimensions on the mounting and shaft, and do not define torque, speed, or electrical ratings. Stepper motors of the same NEMA size can differ greatly in length, winding, and performance.

Dimension values defined by NEMA and size chart

The following table shows examples of dimensions specified for each NEMA size in inches. These have been excerpted and formatted from “Table 2 — Shaft number designation” and “Table 4 — Dimensions for mounting flanges for inch dimension motors” in NEMA ICS 16-2001.

NEMA standard: “Motion/Position Control Motors, Controls and Feedback Devices” 

Example of an external view drawing of the ASPINA stepper motor STA-42D series. The elements enclosed in the square are specified by the NEMA standard.

The diameter of the round flange and the position of the mounting holes are strictly defined by the NEMA standard. For square flanges, the width and height are treated as a reference value in the standard. However, as a customary practice, ASPINA sets those of the square flange of our stepper motors to match the NEMA size number.

At ASPINA, we provide clear information for each model to make it easier for customers who select stepper motors by size. The following table lists our stepper motor models along with their NEMA sizes and typical applications.

The information in this table is current as of the publication date of this article.

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NEMA size specifies only certain physical dimensions of a stepper motor. The following specifications are not defined in NEMA sizes, yet they are critical when selecting the right motor for your application:

Check the mounting dimensions

Determine which NEMA size corresponds to the mounting interface on your equipment. Then, select a motor from the manufacturer’s lineup that can deliver the required torque within that size. However, if there is insufficient axial space, you may need to choose a stepper motor with a larger NEMA size to achieve the necessary torque.

Example of torque ranges (pulse frequency: 1000pps) by step angle, NEMA size, winding type, and axial length for ASPINA stepper motors

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Understand torque requirements

Calculate the torque needed for your application and check its relationship to motor size. In addition to NEMA size, factors such as drive method and the motor’s axial length are important for identifying the right stepper motor.

Consider drive conditions

Review the relationship between drive method and current. The driver’s control method determines the winding configuration, which in turn affects torque, circuit ratings, and the current capacity of your equipment. These considerations help define the rated current.

Review other specifications

Shaft length, the necessity of a gear mounted on the shaft, connector type and position, which may affect mounting, as well as environmental conditions such as temperature are also important considerations.

ASPINA supplies not only standalone stepper motors, but also system products that incorporate drive and control systems as well as mechanical design. These are backed by comprehensive support that extends from prototyping to commercial production and after-sales service.

ASPINA can offer solutions that are tailored to suit the functions and performance demanded by a diverse range of industries, applications, and customer products, as well as your particular production arrangements.

ASPINA supports not only customers who already know their requirements or specifications, but also those who are facing problems at early stages of development.

Do you struggle with the following concerns?

Motor selection

Motor and associated component development

Unique requirement

Seeking answers to these problems? Contact ASPINA, we are here to help.