Why is There a Small Peak in the Torque Curve Before Zero Speed, and Why Doesn't the Curve Extend to Zero?

To understand this, we need to clarify how the torque-speed curve of a stepper motor is plotted and the physical differences between the motor when stationary and when moving. The image below shows the torque curve for the 24E1K-30 stepper motor.

As can be seen from the graph, the curve generally starts from 100 RPM. Here are the key points to understand:

Torque Curve Measurement Method: The torque-speed curve describes the maximum continuous torque the motor can output at different rotational speeds. The word "continuous" is key. The test method typically involves: running the motor at a fixed speed, then gradually increasing the load until the motor loses synchrony (i.e., can no longer follow the commands). The torque value at this point is the maximum continuous torque for that speed.

Holding Torque: At zero speed, the motor is in a stationary, locked state. The torque it can generate in this state is called the "Holding Torque." This is the maximum resistance torque you feel when trying to rotate the rotor by hand while the motor is powered but stationary. This value is usually higher than the continuous torque in the low-speed region.

Why the Curve Doesn't Extend to Zero: Because at the zero-speed point, the motor cannot simultaneously satisfy the conditions of "rotating" and "outputting torque." The torque-speed curve describes performance under dynamic rotating conditions. At zero speed, the motor is static, and its ability to output torque (Holding Torque) is a static characteristic, which is a different concept from the continuous torque under dynamic rotation. Therefore, standard practice is to represent the holding torque with a vertical dashed line or a separate data point, while the dynamic torque curve starts plotting from that "small peak."

Conclusion: At very low speeds, stepper motors are highly susceptible to resonance, making it difficult to measure torque accurately. This is why torque measurement typically starts from around 100 RPM. This article introduces the maximum speeds and recommended operating speeds for various stepper motor sizes: Max. Motor Speed and Recommend Motor Speed | Help Center

Updated on: 26/09/2025