Unipolar and bipolar stepper motors are two common types of stepper motors used in various applications. Here’s a comparison between unipolar and bipolar stepper motors:
Unipolar Stepper Motors:
Coil Arrangement:
- Unipolar stepper motors have two windings per phase, with the center tap of each winding connected to a common wire.
- They typically have six or eight leads: four for the two windings and two or four for the common wire connections.
Control:
- Unipolar stepper motors are easier to control because they require simpler driver circuits.
- They can be driven using dedicated unipolar stepper motor drivers, which activate the windings by applying current through the common wire and the individual windings.
Number of Phases:
- Unipolar stepper motors usually have four or five phases per revolution.
- They tend to have lower torque and efficiency compared to bipolar motors due to their construction.
Wiring:
- Unipolar stepper motors are easier to wire since they have a common wire for each winding.
- However, they may require more wires overall compared to bipolar motors due to the center taps.
Control Complexity:
- Unipolar stepper motors are less efficient compared to bipolar motors because only half of the winding is used at any given time.
Bipolar Stepper Motors:
Coil Arrangement:
- Bipolar stepper motors have a single winding per phase, and the current flow can be reversed to change the direction of rotation.
- They typically have four leads: one for each end of the winding.
Control:
- Bipolar stepper motors require more complex driver circuits to control the current flow and direction of the winding.
- They need H-bridge or full-bridge driver circuits to control the current flow and polarity.
Number of Phases:
- Bipolar stepper motors usually have two phases per revolution.
- They tend to have higher torque and efficiency compared to unipolar motors because all of the winding is used for each step.
Wiring:
- Bipolar stepper motors have simpler wiring compared to unipolar motors since they do not have center taps.
- They have fewer wires overall, making them easier to connect and integrate into systems.
Control Flexibility:
- Bipolar stepper motors offer more control flexibility and can achieve higher torque and efficiency compared to unipolar motors.
- They are widely used in applications requiring precise control, such as CNC machines, 3D printers, and robotics.