Main technical driving modes and types of stepper motor

1.Detailed introduction of stepper motor

A stepper motor is a brushless, synchronous electric motor that converts digital pulses into discrete mechanical steps of rotation. It is used for precision control in applications like 3D printers and CNC machines because its shaft moves in precise, repeatable increments and can hold its position without a feedback sensor. A stepper motor consists of a rotor with a permanent magnet and a stator with windings, and it moves by energizing these windings in a specific sequence. 

2.Working principle of stepper motor

1.Digital pulses to mechanical movement: Each digital pulse sent to the motor's controller causes the rotor to move to the next precise angular position, or "step".

2.Phases: The stator has multiple coils of wire organized into phases. By energizing these phases in a specific sequence, a magnetic field is created that turns the rotor.

3.Precise rotation: The number of steps per revolution is predetermined by the motor's design, and the total angle of rotation is directly proportional to the number of pulses sent.

4.Holding position: A stepper motor can hold its position when a specific phase is energized, even when the motor is off, which is crucial for applications needing precise alignment.        

3.Main technical driving modes of stepper motor

1.The full step is the basic stepping mode used to control the movement of the motor. In this mode, the motor rotates to one full step for every electrical pulse sent to the coil. In a traditional stepper motor, each phase consists of two coils. To take one full step in these motors, one coil of each phase is energized sequentially.By controlling the sequence of energising and duration of each pulse, the motor can either clockwise or anti-clockwise. In a full-step mode, the rotor moves at a specific step angle for each pulse sent to the coil. It provides better torque to the motor but changes from one step to another sometimes creating noise and vibration in some applications.

2.Half-step mode is a stepping mode that offers a balance between full-step and micro-stepping mode. In this mode, the motor takes half the size of the step as compared to the full-step mode steps. In a two-phase stepper motor, the coils are energised in such a way that first activates one coil at a time and then activates two coils simultaneously but at a low current level. It results in smaller steps as compared to full steps.In half-step mode, the motor takes half the step angle for each pulse. This doubles the number of steps as compared to full-step mode but results in smoother operation and better resolution. Half-step mode improves the movement of the motor as smaller steps result in more precise control over the position of the motor and reduce the noise and vibrations.

3.Microstepping mode is an advanced stepping mode used to achieve extremely precise control over the movement of the motor. In this mode, each step is divided into smaller micro steps. As compared to full-step and half-step modes, the micro-stepping mode offers better control over the movement of the motor. In this mode, rather than energizing the coil fully or alternately, it involves applying various levels of current to the motor coil. By precisely changing the current level in the coil, the rotor can hold positions easily. The number of micro steps between each full step of the motor can be several dozen or more.   

4.Main types of stepper motor

1.Hybrid Stepper Motor:The design benefits of variable reluctance (VR) and permanent magnet (PM) stepper motors are combined in hybrid stepper motors. They offer improved performance in terms of precision, torque, and step resolution, making them the most popular type of stepper motor in industrial and commercial applications.Both the rotor and the stator of hybrid stepper motors are toothed, and the rotor has a permanent magnet. This structure results in precise control of step angles—typically 1.8°, though smaller angles like 0.9° are also common.

2.Permanent Magnet (PM) Stepper Motor:PM stepper motors lack the toothed structure present in hybrid stepper motors and instead use permanent magnets in the rotor. Their step angles, which range from 7.5° to 15°, are often bigger. They are more affordable and provide greater torque at lower speeds than hybrid motors, despite their lack of precision.PM motors are often used in applications where high precision isn’t necessary, but simplicity and affordability are preferred.

3.Variable Reluctance (VR) Stepper Motor:There are no permanent magnets in VR stepper motors. They use the magnetic reluctance principle instead. The soft iron rotor shifts to the place of least resistance when the stator poles are turned on. These motors offer fast stepping response and are ideal for high-speed but low-torque applications.Their step angle can be quite small (e.g., 1.2°), and they are often used in systems where lightweight and simple structures are a priority.

4.Synchronous Stepper Motor:Synchronous stepper motors are a subset of stepper motors that maintain rotor position locked to the rotating magnetic field, enabling precise synchronization with the input pulses. They are sometimes considered a broader category under which stepper motors fall, but in this context, we refer specifically to synchronous motors with step characteristics used in control systems requiring exact positioning.Unlike induction motors, synchronous stepper motors rotate at a constant speed determined by the supply frequency and are commonly used where timing and speed precision are essential.