Selection and Calculation of Stepper Motor

Release Time：

2025-03-20

A stepper motor is an actuator that converts electrical pulses into angular displacement. By controlling the number of pulses, the angular displacement is controlled to achieve precise positioning. Under various control signals such as digital, analog, and communication, stepper motors are widely used in various position and speed control applications.

Selection and Calculation of Stepper Motor
A stepper motor is an actuator that converts electrical pulses into angular displacement. By controlling the number of pulses, the angular displacement is controlled to achieve precise positioning. Under various control signals such as digital, analog, and communication, stepper motors are widely used in various position and speed control applications.

load characteristics

Load types: rotating load, linear load, frictional load, gravity load, etc.

Load Inertia (Jload): The moment of inertia of the load about the axis of rotation (unit:) kg·m²）。

Load torque (Tload): Static torque that overcomes friction or gravity (unit:) N·m）。

Motion Parameters

High speed (N_ {\ text {max}} Nmax): High speed required by the load (unit: rpm）。

Acceleration and deceleration time (t_ {\ text {acc}} tacc, t_ {\ text {dec}} tdec): Acceleration and deceleration time (unit: s）。

Positioning accuracy: Step angle (such as 1.8 °, 0.9 °) and driver subdivision settings.

Transmission mechanism parameters

Reduction ratio (ii): If a reducer is used, its amplification effect on torque and speed should be considered.

Transmission efficiency (\ eta η): The transmission efficiency of gears, belts, etc. (usually taken as 0.8-0.95).

Determining the required torque: Static torque is one of the main parameters for selecting a stepper motor. A stepper motor consists of three main elements: step angle, static torque, and current. Once these three elements are determined, the model of the stepper motor is determined.

1. The selection of step angle for the motor depends on the requirements of load accuracy. Convert the small resolution (equivalent) of the load to the motor shaft, and determine how many angles each equivalent motor should walk. The step angle of the motor should be equal to or less than this angle. The step angle of stepper motors on the market generally includes 0.36 degrees/0.72 degrees (five phase motors), 0.9 degrees/1.8 degrees (two and four phase motors), 1.5 degrees/3 degrees (three-phase motors), etc.

2. The selection of static torque is difficult to determine at once for stepper motors, so we often first determine the static torque of the motor. The selection of static torque is based on the load of the motor, which can be divided into two types: inertial load and frictional load. A single inertial load and a single frictional load do not exist. When starting directly (usually at low speed), both types of loads need to be considered. When accelerating, inertial loads are mainly considered, while when running at constant speed, frictional loads only need to be considered. In general, the static torque should be within 2-3 times the frictional load. Once the static torque is selected, the motor base and length can be determined.

3. The selection of current for motors with the same static torque varies greatly due to different current parameters. Based on the torque frequency characteristic curve, the current of the motor should be below the curve.