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The Difference Between Unipolar and Bipolar Stepper Motors

Release Date:2023-09-11
Author:LEESN

Unipolar and bipolar stepper motors are two common configurations of stepper motors, and they differ primarily in their wiring and operation. Here's a breakdown of the key differences between these two types:

  1. Coil Wiring:

    • Unipolar Stepper Motors: Unipolar stepper motors have two windings per phase, and the center tap of each winding is brought out to a separate wire. This configuration results in five or six wires, including the center taps. Unipolar motors are easier to control since they use the center taps to switch current direction, allowing the use of simple transistor switches or driver circuits.
    • Bipolar Stepper Motors: Bipolar stepper motors have only two wires per phase. This means there is no center tap, and the current flows through the coil in both directions. Controlling bipolar motors requires more complex driver circuits capable of reversing the current flow through the coils.
  2. Control Complexity:

    • Unipolar Stepper Motors: Unipolar motors are generally easier to control and require simpler driver electronics. They use the center taps to reverse the direction of current flow, making it convenient for many applications.
    • Bipolar Stepper Motors: Bipolar motors require more complex driver circuits as the direction of current flow needs to be reversed without the use of a center tap. This complexity can lead to more sophisticated control but may also require more advanced electronics.
  3. Torque and Performance:

    • Unipolar Stepper Motors: Unipolar motors typically have lower torque compared to bipolar motors of the same size. This is because only half of the coil winding is active at any given time.
    • Bipolar Stepper Motors: Bipolar motors generally offer higher torque and better performance since the entire coil winding is active throughout the operation.
  4. Applications:

    • Unipolar Stepper Motors: Unipolar motors are often used in applications where simplicity and ease of control are more critical than maximizing torque and performance. Examples include consumer electronics, small robotics, and hobbyist projects.
    • Bipolar Stepper Motors: Bipolar motors are preferred in applications where higher torque, precision, and performance are required. This includes CNC machines, 3D printers, and industrial automation.

In summary, the primary difference between unipolar and bipolar stepper motors lies in their wiring configurations, control complexity, and performance characteristics. Unipolar motors are simpler to control but may offer lower torque, while bipolar motors are more complex to control but provide higher torque and better performance, making them suitable for a wide range of demanding applications.