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About stepper motors
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What was stepper motor?
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Where are the motors used?
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The operation of the stepper motors
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How is the structure of the different drives different?
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What you should pay attention to when buying stepper motors
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Practical advice
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Bottom line
What was stepper motor?
Figure: Square stepper motors with stepper in different sizes
Stepper motors are electric drives that allow the shaft moved by the rotor to a certain angle.
The motors, also known as stepper motors, have the ability, unlike rotary motors, not only to move the connected elements, but also to let them remain in a certain position.
The special feature of stepper motors is that no other components such as rotary encoders or sensors are required to position the shaft. Your position determination is already an integral part of the motor.
This makes them much easier to use than a combination of a motor and a position sensor.
Where are the motors used?
Stepper motors are used where rotary movements with small step angles and precise positioning are required. In robots, for example, they ensure exact movement for pick-and-place tasks, as they allow the necessary fine control. Thanks to their reliability and precise positioning, they can also be found in a wide range of other areas: Craft and machine tools are just as much part of this as they are used in automation, medical or control technology.
The operation of the motors
Stepper motors exist in different versions, but all of them have one
Have similar functionality:
For example, there are reluctance and permanent magnet motors or a combination of both, the hybrid stepper motor. However, the basic operating principle is the same for all.
the internal moving rotor is driven by a variety of coils (1a to 2b) in the external stator.
The windings supplied with current in sequence produce successive magnetic fields which ultimately stimulate the rotary movement of the rotor or allow it to remain exactly at a certain angle.
Figure: Simplified representation of the operation of a stepper motor
How is the structure of the different drives different?
In the reluctance stepper motor, the rotor consists of a toothed soft iron core. The motors are comparatively inexpensive, have an exact step angle and are suitable for higher speeds, but they have only a relatively small torque.
Permanent magnet stepper motors present themselves almost to the contrary. They have a cylindrical, radial magnetized permanent magnet as a rotor. This means that the resolution of the step angle is larger, since fewer coils can be installed, but the motors have a high torque.
Hybrid stepper motors combine the advantages of the two previously mentioned drives. Here the rotor is formed by an axial permanent magnet with toothed caps, which are offset against each other in such a way that north and south poles alternate (see diagram above). Through this structure, they achieve high torques at small and precise step angles.
What you should pay attention to when buying stepper motors
In addition to the advantages and differences described in the individual engine variants, there are a number of other features that you should consider when purchasing:
Control/activation technology
Stepper motors can use unipolar or bipolar control technology. This has an impact on various aspects such as engine speed or connection. Bipolar stepper motors can produce higher speeds depending on the circuit and provide higher torque than unipolar at low speeds. However, they also place greater demands on the respective power supply and are more complicated to connect.
Accuracy
The accuracy of the drives depends on the number of steps per complete revolution. The number of steps is usually between 24 and 200 steps, but now there are also motors with higher numbers. The number of steps is directly linked to the step angle: This is for example 1.8 degrees for 200 steps. This can also be used to make statements about the accuracy of the motor.
Holding torque: /
The holding torque provides information about the torque at which the motor may be loaded when stationary. The holding torque is thus one of the most important key figures, since it must be taken into account for both later use and for safe commissioning.
Protection class
The degree of protection of the motor provides information about the areas of application for which the drive is later suitable with which environmental influences. The degree of protection is usually specified in accordance with the international IP standard.
Practical tip: Built-in controls
Step motors are sometimes already available with integrated controls, such as encoders, to control the steps taken. These can be a worthwhile alternative, especially for automation processes, or a supplement in the field of computerized numerical control (CNC). If you select a product with control, you must pay attention to the correct interfaces.
Bottom line
Stepper motors offer simple and reliable solutions for all pending positioning tasks. With the information presented here, it is also possible for you to find the right product for your application.