Stepper motors are widely used in precision control systems due to their ability to convert electrical pulses into precise mechanical movements. One of the key parameters that define a stepper motor’s performance is its inherent step angle, which refers to the angle the motor rotates with each pulse it receives from the control system. This value is set at the factory and varies depending on the motor type. For example, the FY56ES300A motor has an inherent step angle of 0.9° for half-step operation and 1.8° for full-step operation. However, the actual step angle during operation may differ based on the driver used.
The number of phases in a stepper motor also plays a crucial role in determining its step angle. Common types include two-phase, three-phase, four-phase, and five-phase motors. Each phase configuration affects the motor's resolution and performance. Two-phase motors typically have a step angle of 0.9°/1.8°, while three-phase motors offer finer steps such as 0.75°/1.5°, and five-phase motors can achieve even smaller steps like 0.36°/0.72°. While increasing the number of phases improves accuracy and smoothness, it also increases complexity and cost.
Holding torque, also known as maximum static torque, is the maximum torque the motor can hold when energized but not rotating. It is a critical parameter for measuring a motor's strength and is often used as a reference point for low-speed performance. As speed increases, the output torque decreases, which is why holding torque is essential for applications requiring high force at rest. For instance, a 2N.m motor usually refers to its holding torque unless otherwise specified.
Step accuracy determines how precisely the motor moves with each pulse. It can be measured in terms of positioning error or step angle error. The moment-angle characteristic describes the relationship between the static torque and the angular displacement from the equilibrium position. This feature is important for understanding how the motor behaves under different load conditions.
Static temperature rise refers to the increase in temperature when the motor is stationary and operating at rated current. Dynamic temperature rise, on the other hand, measures the temperature increase during continuous operation under no-load conditions. Both factors are important for assessing the motor's thermal performance and long-term reliability.
Torque characteristics describe the relationship between the motor’s torque and the excitation current when only one phase is energized. Starting torque characteristics define the relationship between the starting frequency and the load torque, which is essential for understanding the motor’s acceleration capabilities. The lift frequency time indicates how quickly the motor can change its speed from the starting frequency to the maximum operating frequency or vice versa.
Detent torque is the torque that holds the rotor in place when the motor is not energized. However, this concept is more applicable to permanent magnet stepper motors. In reactive stepper motors, where the rotor is not made of permanent magnet material, detent torque does not exist. Therefore, it is important to understand the type of motor being used before interpreting this parameter.
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