What is a stepper motor?
A stepper motor is an actuator that is one of the key products of mechatronics and has been widely used in various automation equipment. It’s an open-loop control element that converts an electrical pulse signal into an angular or linear displacement. Upon receiving a pulse signal, the stepper driver drives the stepper motor to rotate a fixed angle (i.e., stepping angle) in the determined direction. Angular displacement can be controlled by controlling the number of pulses to achieve accurate positioning.
Types of stepper motors
There are three basic types of stepper motors: permanent magnet stepper motor (PM), variable reluctance stepper motor (VR), and hybrid stepper motor (HY).
1. Permanent magnet stepper motor. With a permanent magnet rotor and a stepping angle of 7.5 degrees or 15 degrees, this type of stepper motor is usually a two-phase motor, and has small torque and volume. Its stator is similar to that of a conventional two or three phase induction motor. Its rotor is made of permanent magnets, so the motor needs no external excitation and it becomes very useful in applications such as toys, and small motors, etc.
2. Variable reluctance stepper motor. As one of the three-phase high quality stepper motors, this kind of stepper motor has a stepping angle of 1.5 degrees and can achieve large torque output, but has very large noise and vibration. Its electromagnetic stator has a magnetically soft iron rotor, whose teeth and slots are similar to the rotor of an inductor alternator.
3. Hybrid stepper motor. With the advantages of both permanent magnet and variable reluctance stepper motors, this type of motor includes two-phase, four-phase and five-phase motors. The stepping angle of a two-phase stepper motor is generally 1.8 degrees, while the stepping angle of a five-phase stepper motor is generally 0.72 degrees.
Characteristics of hybrid stepper motor
1. High output torque and high speed, and accurate positioning control.
2. The motor generates little heat, low noise and high efficiency.
3. High torque values can be generated by using small size.
4. It can stop at high speed smoothly and quickly, and has no zero-speed oscillation and small vibration noise.
5. Fast response time enables the hybrid stepper motor to be suitable for frequent start/stop situations.
Pros and cons of hybrid stepper motor
Pros: With minimal step and stepping rate, the motor offers high torque that has de-energized windings, and operates with increased performance even at minimal speeds.
Cons: Its inertia is more; its design, weight and construction is complicated; its reliability and efficiency gets disturbed when the magnetic strength is changed.
Working principle of hybrid stepper motor
The structure of a hybrid stepper motor is different from that of the variable reluctance stepper motor, according to stepper motor manufacturers. For the latter one, the stator and rotor are integrated; while for the former one, the stator and rotor are divided into two sections with small teeth distributed on the poles. The two tooth slots of the stator are not dislocated and windings are arranged on them. Obviously, all teeth on the same segment of the rotor piece have the same polarity, while two different segments of the rotor piece have opposite polarity.
The rotor of the hybrid stepper motor is magnetic, so the torque generated at the same stator current is greater than that of the variable reluctance stepper motor, and its stepping angle is usually smaller. Therefore, economic CNC machine tools generally need to be driven by a hybrid stepper motor. However, the rapidity of a hybrid stepper motor is lower than that of the variable reluctance stepper motor due to its complicated rotor structure and large rotor inertia.
Differences between hybrid stepper motor and variable reluctance stepper motor
The main difference between hybrid stepper motors and variable reluctance stepper motors is that when the magnetized permanent magnetic material is demagnetized, oscillation points and out-of-step zones will appear.
1. Structure and material. Permanent magnetic materials are provided inside a hybrid stepper motor, making the hybrid motor have self resistance (that is, there is a certain self-locking force when the motor is not charged), while a variable reluctance stepper motor has no self resistance.
2. Operating performance. A hybrid stepper motor runs relatively smoothly, with relatively high output torque and low operating sound.
3. Price. A variable reluctance stepper motor is cheaper than a hybrid stepper motor.
Applications of hybrid stepper motor
The hybrid stepper motor can be mainly applied to the applications that need quiet and smooth operation, motion control positioning systems, computer and 3D printers, image scanners, and floppy disk drives.
How to choose a hybrid stepper motor?
Many stepper motor manufacturers provide different types of hybrid stepper motors, and you may wonder how to find the best one that suits you. In fact, you should take several factors into consideration when selecting a stepper motor: the method to coupling the motor to the load, the speed requirements for the load, the torque that is required to move the load, and the degree of accuracy when positioning the load, etc.
Changzhou ACT Motor Co., Ltd., one of the most innovative high-tech companies in China focusing on the production of stepper motors and related electrical control systems, offers a wide range of hybrid stepper motors, including two-phase or four-phase hybrid stepper motor, planetary gearbox stepper motor, eccentric gearbox stepper motor, and integrated stepper motor, etc. Here ACT Motor provides several normal hybrid stepper motor selection steps for your reference to find high quality stepper motors.
First, determine the drive mechanism component and required specifications, such as mechanism, rough dimensions, distances moved, and positioning period. Second, calculate the required resolution and determine whether a motor or a geared motor is to be used. Third, determine the operating pattern that meets the required specifications. Fourth, calculate the load torque and acceleration torque and then determine the required torque. Last, select the motor based on the required torque and speed-torque characteristics.
Post time: May-23-2022
