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What is a PM Stepper Motor?

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What is a PM Stepper Motor?

A permanent magnet stepper motor (PM stepper motor) is a type of stepper motor that uses a permanent magnet as the rotor instead of a traditional wound rotor. This allows for a simpler and more compact design, with high torque and precise motion control.

Construction of a PM Motor

The construction of a PM stepper motor is relatively simple; it consists of a rotor and stator. The rotor is made up of two permanent magnets and the stator is constructed of a series of electromagnetic coils. The stator typically has two or more phases, each phase consisting of a pair of coils. The stator is also made of soft magnetic material with teeth or poles that are arranged in a circular pattern. The rotor is typically made of a soft magnetic material, such as iron, and contains teeth or poles that align with the stator teeth or poles. The number of poles on the rotor and stator determines the step angle, with higher pole counts resulting in smaller step angles and smoother motion. These parts all come together to make a PM stepper motor. 

Working Principle

A PM stepper motor operates based on the principle of magnetic attraction and repulsion. As mentioned, the construction of the rotor is such that there are two permanent magnets. The stator is made up of two or more electric coils that are arranged in a circular pattern around the rotor. When a current is applied to one of the coils, it generates a magnetic field, which attracts the permanent magnets in the rotor toward it. As the rotor moves towards the magnetic field, it aligns with the next set of poles in the stator, and the current to the previous coil is turned off. This process is repeated sequentially for each coil, causing the rotor to move in a precise and controlled manner.

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Advantages of PM Stepper Motors

PM Stepper motors have many advantages over other types of motors leading to them being used in a wide range of applications. Some of the most common advantages of PM stepper motors include: 

  • Compact Size: For their compact size and low cost, PM steppers can deliver a suitable amount of torque. 
  • Simplified Design: The absence of a wound rotor and the use of a permanent magnet rotor simplifies the motor design, resulting in a more compact and lightweight motor.
  • Low Cost: PM stepper motors have a simple construction, making them easy and cheap to manufacture. They also do not require any feedback mechanisms, reducing the overall cost and complexity of the motion system.
  • Energy Efficiency: Requiring less energy than other types of motors, PM stepper motors only require power during the step sequence, reducing the overall power consumption of the system.

PM Stepper Motor Applications

PM stepper motors are used in a wide range of applications due to their ability to achieve positioning, high torque output, and energy efficiency. Some typical applications of PM stepper motors include:

  • Robotics: In robotic systems, they are utilized for motion control and essential positioning.
  • Consumer Electronics: Different consumer electronics such as cameras, printers, and scanners employ them to control movement and positioning.
  • Automotive: Applications in the automotive industry, such as power window systems, seat adjusters, and headlight leveling systems, use them.
  • Industrial Automation: They are used in various industrial automation applications, such as conveyor systems, assembly lines, and packaging machinery.
  • Textile Machinery: Regarding textile machinery like looms and knitting machines, they are utilized to manage the movement of the fabric.
  • ATMs and Vending Machines: Due to their cheap cost and basic positioning control, PM steppers are used in vending machines to retrieve an item and operate the bill acceptor



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PM stepper motors are essential in various industrial and consumer applications to provide precise positioning, smooth performance at low speeds, and a decent amount of torque in a compact design. They are suitable for a wide range of applications. Understanding the construction and operation of PM stepper motors is crucial for selecting the correct motor for your next application and ensuring its optimal performance

PM Stepper Motors
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