There are two types of stepper motors: bipolar-connected and unipolar-connected, each with its own advantages and disadvantages, so you need to understand their characteristics and choose them according to your application needs.
Bipolar connection
The bipolar connection method, shown in the figure, uses a drive method in which current flows in both directions in one winding (bipolar drive). The motor in this way has a simpler structure and fewer terminals, but the drive circuit is more complex because the polarity of one terminal must be controlled. However, this type of motor has good winding utilization and allows fine control, so high output torque can be obtained. In addition, it is possible to reduce the counter-electromotive force generated in the coil, so motor drives with lower withstand voltage can be used.
Single pole connection
As shown in the figure, the single-pole connection has a central tap and uses a drive method in which current always flows in a fixed direction in one winding (single-pole drive). Although the structure of a stepper motor is more complex, the drive circuit of a stepper motor is simpler because only the current ON/OFF control is required. However, the utilization of its winding is poor, and only about half of the output torque can be obtained compared to a bipolar connection. In addition, since current ON/OFF generates a high counter-electromotive force in the coil, a motor driver with high withstand voltage is required.
Key Points
Bipolar connection of stepper motors
A drive method in which current flows in both directions in one winding (bipolar drive) is used.
Simple structure, but complex drive circuit for stepper motors.
The winding utilization is good and fine control is possible, so stepper motors can obtain high output torque.
The counter-electromotive force generated in the coil can be reduced, so motor drivers with low voltage withstand can be used.
Single pole connection of stepper motors
A drive method that has a center tap and uses a winding in which current always flows in a fixed direction (single-pole drive).
Complex structure, but simple drive circuit for stepper motors.
Poor winding utilization, only about half of the output torque of a stepper motor can be obtained compared to a bipolar connection.
A motor driver with high withstand voltage is required because a high counter-electromotive force is generated in the coil.
Post time: Nov-09-2022