Comparison of Characteristics: Long-Body vs. Short-Body Stepper Motors

In stepper motor selection, body length is a key parameter influencing performance suitability. Long-body and short-body motors exhibit significant differences in torque output, response speed, cooling requirements, and power supply compatibility, which directly affect their applicability in various scenarios.

Note: For common frame sizes such as NEMA 23, NEMA 17, and NEMA 34, the term "long-body" is not defined by the NEMA standard itself, but rather reflects industry conventions and manufacturer-specific designs.

Characteristic Comparison:

• Torque Performance: Long-body motors, due to their higher rotational inertia, experience more significant current loss during startup. Their actual maximum running torque is typically only about 70% of the holding torque, showing notable torque degradation. In contrast, short-body motors benefit from lower rotational inertia, resulting in minimal startup current loss. The deviation between their running torque and holding torque is generally kept within 10%–15%, offering higher output stability.

• Startup Response: Influenced by differences in rotational inertia, the startup characteristics also vary. Long-body motors require more time to accelerate from standstill to rated speed, exhibiting a lag in response. Short-body motors, with their lower inertial resistance, offer rapid startup and are better suited for applications requiring frequent start-stop cycles.

• Cooling Requirements: Long-body motors feature longer stator stacks and windings. Combined with the additional heat generated from higher startup current loss, they demand more robust cooling solutions—often requiring optimized housing designs or additional cooling components—to ensure stable operation. Short-body motors have more compact windings and generate less heat, allowing standard cooling structures to suffice without extra cost.

• Power Supply Compatibility: Long-body motors require drivers with higher output capacity to compensate for torque degradation and ensure adequate power output. Short-body motors have lower demands on driver performance; standard stepper motor drivers are generally sufficient, helping reduce overall system costs.

• Back-EMF Characteristics: Back electromotive force (Back-EMF), primarily generated when windings cut through the magnetic field during rotation, is directly related to motor length. To achieve higher torque, long-body motors are often designed with more winding turns and longer magnetic paths. This results in a greater range and number of windings cutting the magnetic field during rotation, leading to a higher Back-EMF peak. Short-body motors, with fewer winding turns and more compact magnetic circuits, exhibit significantly lower Back-EMF peaks.

Summary: The two motor types offer complementary characteristics: long-body motors are suitable for low-speed, high-torque applications requiring sustained force, while short-body motors are better suited for high-speed, light-load applications demanding high dynamic response.

Updated on: 23/09/2025