Six Common Stepper Motor Questions Engineers Still Ask
Despite being one of the most widely used motion technologies, stepper motors still generate many questions during system design and commissioning. These common stepper motor questions often come from real-world performance gaps between datasheets and actual machine behavior.
Based on field experience across packaging equipment, CNC machines, 3D printers, and automated handling systems, the following six questions appear again and again. Understanding them early can save time, cost, and unnecessary redesigns.
1. Why Is the Actual Torque Much Lower Than the Rated Torque?
One of the most frequent stepper motor questions relates to torque. Many users select a motor based solely on its holding torque value, only to find that the motor struggles once it starts moving.
Holding torque is measured at standstill. As soon as the motor rotates, available torque drops sharply, especially at higher speeds. This is why speed–torque curves are far more important than the holding torque number.
A practical rule is to design with a safety margin. Instead of using the full published curve, assume only 50–70% of the stall torque is usable in continuous operation.
2. Is It Normal for a Stepper Motor to Run Very Hot?
Yes—this is completely normal. Stepper motors are designed to operate at high temperatures. Most industrial models use Class B insulation, allowing winding temperatures up to 130°C.
Because stepper systems operate in open-loop control, the drive supplies constant current regardless of load. This maximizes torque availability but also results in higher heat generation, even at standstill.
If surface temperatures exceed expectations, reducing current via the drive settings or enabling idle current reduction can significantly lower heat without sacrificing performance.
3. Can I Use a 12V Power Supply for My Stepper Motor?
Supply voltage is directly related to achievable speed. While the motor’s rated voltage may appear low, that value is derived from winding resistance and rated current—not dynamic operation.
When the motor rotates, it generates back EMF that limits current rise. To maintain torque at speed, the drive requires a much higher supply voltage.
Always reference speed–torque curves published with the same drive and voltage. Using a 12V supply when the curve was generated at 48V will result in dramatically reduced performance.
4. Why Can’t I Drive a Stepper Motor Directly from PLC Outputs?
Another common stepper motor question is whether a dedicated drive is really necessary. Technically, simple stepping can be achieved using multiple PLC outputs—but this approach ignores current regulation, microstepping, and acceleration control.
A proper stepper motor drive regulates phase current using PWM control, overcomes back EMF, and enables smooth microstepping motion. Advanced drives also manage acceleration profiles internally, reducing mechanical shock.
For any industrial or production system, a dedicated drive is not optional—it is essential.
5. Why Is the Stepper Motor So Noisy at Low Speed?
Stepper motor noise at low speed is typically caused by mechanical resonance. Each step excites the motor’s natural frequency, especially when running in full-step mode between 1–5 rps.
Noise is often worst when the motor is tested unloaded. Once mounted and coupled to a real load, resonance usually decreases significantly.
Microstepping, mechanical damping, or drives with built-in anti-resonance algorithms can further reduce vibration and acoustic noise.
6. Do I Need an Encoder to Use a Stepper Motor?
No encoder is required for standard open-loop stepper operation. Stepper motors are unique in their ability to position accurately without feedback, provided the load and motion profile are predictable.
Open-loop control works well when loads are stable, speeds are moderate, and missed steps are not safety-critical. If conditions vary, adding feedback can enhance reliability or enable closed-loop operation.
Many modern systems start with open-loop control and upgrade later if the application demands it.
Final Thoughts
These common stepper motor questions highlight the gap between theory and real-world motion control. Most issues are not motor defects but system-level misunderstandings involving torque curves, voltage, resonance, and drive configuration.
Selecting the right motor, matching it with a suitable drive, and configuring it correctly will deliver reliable performance in the majority of industrial automation applications.
If you are unsure about motor sizing, drive selection, or operating margins, it’s often best to discuss your application with an experienced motion control engineer.
You can contact the HDBMOTOR engineering team to review your requirements and get practical recommendations before finalizing your design.