Learn about stepper motors with Cooldog

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Learn about stepper motors with Cooldog [Copy link]

1. Classification and advantages and disadvantages of stepper motors

Reactive stepper motor: Reactive stepper motor is a traditional stepper motor that rotates by the interaction between the magnetic rotor core and the pulsed electromagnetic field generated by the stator. The working principle of the reactive stepper motor is relatively simple. There are many small teeth evenly distributed on the rotor. The stator teeth have three excitation windings, and their geometric axes are staggered with the rotor tooth axes respectively. The position and speed of the motor are in one-to-one correspondence with the number of conduction times (number of pulses) and the frequency. The direction is determined by the order of conduction. The market is generally dominated by two-, three-, four-, and five-phase reactive steppers. Reactive stepper motors are characterized by simple structure and durability. Some countries also call them variable reluctance stepper motors. Advantages and Disadvantages: Advantages: high torque-inertia ratio; high stepping frequency; fast frequency response; the rotor can rotate freely when power is not supplied; simple mechanical structure and long life; can rotate in both directions; has appropriate damping; normal motor has no step-out zone. Disadvantages: no positioning torque when power is not supplied; oscillation and overshoot at each step. Permanent magnet stepper motor: Permanent magnet stepper motor, also known as PM stepper motor. The rotor uses permanent magnet. The stator of this stepper motor is stamped into claw-shaped tooth poles, and the rotor uses radial multi-pole magnetized permanent magnet. This motor is low-cost. Principle: The magnetic field generated by the direction of the coil current repel each other with the rotor magnetic field, so that the motor rotates forward/reverse. Permanent magnet stepper motors are divided into 2-phase and 4-phase, with small torque and volume. The step angles are as follows: 5.625°/7.5°/11.25°/15°. The motor has two parts: the rotor and the stator: generally, the stator is a coil and the rotor is a permanent magnet; it can also be a stator with a permanent magnet and a rotor with a coil. Advantages and Disadvantages: Advantages: It is characterized by good dynamic performance and large output torque. Disadvantages: The motor has poor accuracy and a large step angle (generally 7.5° or 15°). Hybrid stepper motor: What we often use now is the hybrid stepper motor, which is a stepper motor designed by combining the advantages of permanent magnet and reaction. It is divided into two-phase, three-phase and five-phase. The two-phase step angle is generally 1.8 degrees, the three-phase step angle is generally 1.2 degrees, and the five-phase step angle is generally 0.72 degrees. The rotor of the hybrid stepper motor is magnetic, so the torque generated under the same stator current is greater than that of the reactive stepper motor, and its step angle is usually smaller. Therefore, economical CNC machine tools generally need to be driven by hybrid stepper motors. However, the structure of the hybrid rotor is more complex, the rotor inertia is large, and its speed is lower than that of the reactive stepper motor. Advantages and Disadvantages: Advantages: The torque-inertia is smaller than that of the reactive type; the step frequency is high, which is similar to the reactive type, and the frequency response is fast; the rotor can be self-locking when not powered; it can rotate in both directions; there is internal damping; there is no oscillation point when the permanent magnet is not demagnetized; the step angle can be as small as the reactive type; it can be used as a low-speed synchronous motor. Disadvantages: The output is smaller than the reactive type, there are oscillation points and out-of-step areas when the permanent magnet is demagnetized; the permanent magnet is easy to demagnetize; the number of phases cannot be selected at will.

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