Holding torque, also known as static torque, refers to the force that the stator exerts on the rotor when the stepper motor is energized but not rotating. This torque is crucial because it represents the maximum torque the motor can hold when stationary. At low speeds, the torque of a stepper motor is close to its holding torque, but as speed increases, the torque drops rapidly, and so does the output power. Therefore, holding torque is one of the most important parameters used to evaluate a stepper motor’s load capacity.
First, consider the holding torque. It is a key factor in determining the motor’s ability to carry a load. For example, a motor rated at 1N.m typically means its holding torque is 1N.m. Choosing the right holding torque ensures the motor can handle the required workload without overheating or losing steps.
Second, choose the number of phases. Two-phase motors are cost-effective, with a step angle of at least 1.8 degrees. However, they tend to vibrate more at low speeds and have lower high-speed performance. Three-phase motors offer smaller step angles (at least 1.2 degrees), reduced vibration, and better low-speed performance, with speeds up to 30–50% higher than two-phase motors. Five-phase motors provide even finer control and smoother operation, though they come at a higher cost and are ideal for precision applications.
Third, select the motor based on the application. The selection process should start with understanding the load characteristics. Compare the static torque and torque-speed curves of different motor types to find the best match. If high accuracy is needed, use mechanical reduction systems to optimize performance. Avoid operating the motor in its vibration zone—adjust voltage, current, or add damping if necessary. For power supply, DC voltages between 24V and 36V are common, while larger motors may require higher voltages. High-inertia loads need motors with larger frame sizes. For high-speed and high-inertia applications, gradually increase the frequency to prevent stepping loss and reduce noise. When torque exceeds 40Nm or speeds go beyond 1000RPM, consider using a servo motor instead, as they can operate at much higher speeds and provide better control.
Fourth, select the driver and subdivision settings. Avoid full-step mode due to increased vibration. Use drivers with lower current, higher inductance, and lower voltage for smoother operation. If high precision or low vibration is required, use a subdivision driver. For high-torque motors, a high-voltage driver is recommended to improve high-speed performance. If the motor runs at high speed with low accuracy requirements, avoid high subdivision settings to save costs. For low-speed applications, use a high subdivision setting to ensure smooth motion and reduce noise. Ultimately, the choice of subdivision should be based on factors like motor speed, load torque, gear setup, accuracy needs, and noise level.
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