(1) Principle of reactive stepping motor
The working principle of the reactive stepping motor is relatively simple. The principle of a three-phase reactive stepping motor will be described below.
1. Structure:
The rotor of the motor is evenly distributed with many small teeth. The stator teeth have three excitation windings, and their geometric axes are sequentially shifted from the rotor tooth axis. 0, 1/3 て, 2/3 て, (the distance between the axes of the adjacent two rotor teeth is the pitch of the tooth), that is, A is aligned with the tooth 1, and B and the tooth 2 are 1/3 turn to the right. C and tooth 3 are shifted to the right by 2/3て, A’ is aligned with tooth 5 (A’ is A, tooth 5 is tooth 1)
2, rotation:
If the phase A is energized and the B and C phases are not energized, the teeth 1 are aligned with A due to the action of the magnetic field (the rotor is not subject to any force and below). If phase B is energized, when phase A and phase C are not energized, tooth 2 should be aligned with B. At this time, the rotor is shifted to the right by 1/3て, at which time the teeth 3 and C are offset by 1/3て, and teeth 4 and A are Offset (て-1/3て)=2/3て. If the C phase is energized, the A and B phases are not energized, and the tooth 3 should be aligned with C. At this time, the rotor is shifted to the right by 1/3 て, and the tooth 4 is aligned with the A offset by 1/3 此时. If the A phase is energized, the B and C phases are not energized, the teeth 4 are aligned with A, and the rotor is shifted to the right by 1/3 て so that the A, B, C, and A are respectively energized, and the teeth 4 (ie, the teeth of the tooth 1) Move to phase A, the motor rotor turns to the right by a pitch. If the A, B, C, A… is continuously energized, the motor rotates 1/3 turn per step (per pulse) and rotates to the right. If A, C, B, A… is energized, the motor will reverse.
It can be seen that the position and speed of the motor are in a one-to-one correspondence between the number of times of conduction (number of pulses) and the frequency. The direction is determined by the order of conduction.
However, due to the consideration of torque, stability, noise and angle reduction. The conductive state of A-AB-B-BC-C-CA-A is often used, so that 1/3 每 of each step is changed to 1/6 て. Even through the different combinations of two-phase currents, the 1/3 turns into 1/12 て, 1/24 て, which is the basic theoretical basis for the motor subdivision drive.
It is not difficult to introduce: there is m-phase excitation winding on the stator of the motor, and its axis is offset from the rotor tooth axis by 1/m, 2/m…(m-1)/m,1 respectively. And the conduction of the motor in a certain phase sequence can be controlled by forward and reverse – this is the physical condition of the stepper motor rotation. As long as this condition is met, we can theoretically manufacture stepper motors of any phase. For cost and other considerations, the market generally has two, three, four, and five phases.
3. Torque:
When the motor is energized, a magnetic field (magnetic flux Ф) will be generated between the stator and rotor. When the rotor and the stator are offset by a certain angle, the force F is proportional to (dФ/dθ). The magnetic flux Ф=Br*SBr is magnetically dense, and S is the magnetic conductive area. F is proportional to L*D*Br, L is the effective length of the iron core, D is the rotor diameter Br=N I/RN I is the number of excitation winding amps (current multiplied by the number of turns) R is the magnetic resistance.
The torque is proportional to the effective volume of the motor * ampere number * magnetic density (only linear state is considered). Therefore, the larger the effective volume of the motor, the larger the number of excitation ampere, the smaller the air gap between the stator and rotor, the greater the motor torque, and vice versa. Of course.
(2) Characteristics and classification of inductive stepper motor
1. Features:
Compared with the traditional reactive stepping motor, the inductive stepping motor has a permanent magnet on the structure to provide the working point of the soft magnetic material, and the stator excitation only needs to provide a varying magnetic field without providing the working point of the magnetic material. The energy consumption is high, so the motor has high efficiency, low current and low heat generation. Due to the existence of permanent magnets, the motor has a strong back EMF, and its own damping effect is better, making it relatively stable during operation, low noise, and low frequency vibration.
The inductive stepper motor can be regarded as a low-speed synchronous motor to some extent. A four-phase motor can be operated in four phases or in two phases. (Bipolar voltage drive must be used), while reactive motors cannot. For example: four-phase, eight-phase operation (A-AB-B-BC-C-CD-D-DA-A) can completely adopt the two-phase eight-beat operation mode. It is not difficult to find that the condition is C=, D=.
The internal winding of a two-phase motor is exactly the same as that of the four-phase motor. The low-power motor is usually directly connected to two-phase, and the motor with larger power is used to flexibly change the dynamic characteristics of the motor for convenient use. Lead wire (four-phase), when used, can be used as a four-phase motor, and can be used as a two-phase motor winding in series or in parallel.
2, classification
Inductive stepper motors can be divided into two phases: two-phase motors, three-phase motors, four-phase motors, five-phase motors, and so on. The frame number (motor outer diameter) can be divided into: 42BYG (BYG is the induction stepper motor code), 57BYG, 86BYG, 110BYG, (international standard), and like 70BYG, 90BYG, 130BYG, etc. are domestic.