A stepper motor is an open-loop controlled motor that converts electrical pulse signals into angular or linear displacement. It is a primary actuator in modern digital program control systems and has extremely wide applications. Under non-overload conditions, the motor's speed and stopping position depend only on the frequency and number of pulse signals, and are unaffected by load changes. When the stepper driver receives a pulse signal, it drives the stepper motor to rotate a fixed angle in a set direction, called the "step angle." Its rotation occurs step by step at fixed angles. The angular displacement can be controlled by controlling the number of pulses, thus achieving accurate positioning; simultaneously, the motor's speed and acceleration can be controlled by controlling the pulse frequency, thus achieving speed regulation.
Main categories
Stepper motors can be classified into several types based on their structural form, including Variable Reluctance (VR) stepper motors, Permanent Magnet (PM) stepper motors, Hybrid Stepping (HS) stepper motors, single-phase stepper motors, and planar stepper motors.
Wiring method
The difference between four-wire and six-wire stepper motors lies in the flexibility of connection to the driver. Two-phase four-wire stepper motors can only use bipolar drivers.
A two-phase six-wire stepper motor can be driven by either a bipolar or a unipolar driver.
The following diagrams illustrate the differences in the connection methods for two-phase six-wire leads.
Connect to a bipolar driver. Leave center taps 2 and 5 unconnected in the diagram; only connect the two leads at both ends. This essentially connects the two phase coils of each group in series, resulting in higher torque and efficiency, but poor high-speed performance. This connection method is preferred for low-speed, high-torque applications. However, it's important to note that the maximum operating current should be less than the rated current, approximately 0.7 times. For example, if the rated current is 3A, the actual operating current should be set to around 2.1A according to the connection shown in the diagram.
The two connections shown in the image above achieve the same effect: the tap is connected to one end, while the other end remains unconnected. This connection method provides better high-speed motor performance, but each phase has one set of coils idle, resulting in lower blocking torque and efficiency; it is preferred for applications with relatively high operating speeds. The maximum operating current for both connections is the motor's rated current.
The above two methods describe connections to a unipolar driver. Both unipolar drive connection methods are identical for the motor; the difference lies in the internal processing of the drive. The power utilization rate of a unipolar drive is lower than that of a bipolar drive. The maximum operating current of the motor is the same as its nominal rated current.
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