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The stepper motor is an open-loop control element that converts an electrical pulse signal into angular displacement or line displacement. In the case of non-overload, the motor speed, stop the location depends only on the pulse signal frequency and pulse number, without the impact of load changes, that is, to the motor plus a pulse signal, the motor is a step angle. The existence of this linear relationship, coupled with the stepper motor only periodic error without cumulative error and so on. So that in the speed, position and other control areas with stepper motor to control the change is very simple.
Although the stepper motor has been widely used, but the stepper motor and can not like ordinary DC motor, AC motor under normal use. It must be double ring pulse signal, power drive circuit and other components of the control system can be used. So it is not easy to use stepper motor, it involves the mechanical, electrical, electronics and computer and many other professional knowledge.
At present, the production of stepper motor manufacturers do a lot, but with professional and technical personnel, to develop their own, the development of the manufacturers are very few, most of the manufacturers only one or twenty people, even the most basic equipment are not. Only in a blind imitation stage. This gives the user in the product selection, use caused a lot of trouble. Signed in the above situation, we decided to take a wide range of induction sub-stepper motor as an example. Describe its basic working principle. Hope to the majority of users in the selection, use, and machine improvement to help.
Second, the induction sub-type stepper motor works
(A) reactive stepper motor principle
As the reactive stepper motor works is relatively simple. The following describes the three-phase reaction stepper motor principle.
The motor rotor is evenly distributed with many small teeth, the stator teeth have three excitation winding, and their geometric axes are respectively shifted from the rotor tooth axis. 0, 1/3 te, 2/3 te, (the distance between the adjacent two teeth of the teeth to the distance to te), that is, A and teeth 1 aligned, B and teeth 2 right 1 / C and 3 are shifted right by 2/3, A 'is aligned with tooth 5, (A' is A, tooth 5 is tooth 1)
If the A-phase power, B, C phase is not energized, due to the role of the magnetic field, teeth 1 and A aligned, (the rotor is not subject to any force below). If the B phase power, A, C phase is not energized, the teeth should be aligned with B, then the rotor moved to the right 1/3 て, then teeth 3 and C offset of 1/3 te, teeth 4 and A Offset (て -1/3 て) = 2/3 te. Such as the C-phase power, A, B phase is not power, teeth 3 should be aligned with C, then the rotor and then moved to the right 1/3 て, this time 4 and A offset 1/3 て alignment. If the A phase is energized, B, C phase is not energized, the teeth 4 are aligned with A, and the rotor is moved to the right by 1/3 ¢ so that the A, B, C and A are energized respectively, ) To the A phase, the motor rotor to the right turn a pitch, if constantly press A, B, C, A ... ... power, the motor on each step (per pulse) 1/3 te, turn right. Such as by A, C, B, A ... ... power, the motor on the reverse.
It can be seen: the location and speed of the motor by the number of times (pulse number) and frequency into a one-to-one relationship. And the direction is determined by the order of conduction.
However, in terms of torque, smooth, noise and reduce the angle of consideration. Often use A-AB-B-BC-C-CA-A this conductive state, so that the original 1/3 て each change to 1/6 te. And even through the combination of different two-phase current, so that 1/3 te to 1/12 te, 1/24 te, which is the basic theoretical basis for motor subdivision drive.
It is not difficult to introduce: the motor stator has m-phase excitation around the shaft, respectively, and the rotor tooth axis offset 1 / m, 2 / m ... (m-1) / m, And the conductive phase can be controlled by a certain phase sequence motor - this is the physical condition of the stepping motor rotation. As long as we meet the conditions we can create any phase of the stepper motor, for cost and other considerations, the market generally to two, three, four, five as much.
When the motor is energized, a magnetic field (magnetic flux Ф) is generated between the stator and rotor. When the rotor is shifted from the stator by a certain angle, the force F is proportional to (dФ / dθ). The magnetic flux Ф = Br * S Br is the magnetic flux, The area F is proportional to L * D * Br is the effective length of the iron core, D is the rotor diameter Br = N · I / RN · I is the number of turns on the impedance of the loop (current multiplier) R is the reluctance.
Torque = force * radius
Torque and motor effective volume * ampere-turns * magnetic density is proportional to (only consider the linear state) Therefore, the greater the effective volume of the motor, the greater the number of excitation turns, the smaller the inter-rotor gap, the greater the motor torque, Then.
(2) Inductive sub-stepper motor
Inductive sub-stepper motor Compared with the traditional reactive stepping motor, the structure of the rotor plus a permanent magnet to provide soft magnetic material operating point, and stator excitation only to provide a change in the magnetic field without the need to provide magnetic material operating point Of the energy consumption, so the motor efficiency, current is small, low heat. Due to the presence of permanent magnets, the motor has a strong back electromotive force, its own damping effect is better, so that it is relatively smooth in the process of running, low noise, low frequency vibration.
Inductive sub-stepper motor can be seen as a low-speed synchronous motor to some extent. A four-phase motor can be used for four-phase operation, can also be used for two-phase operation. (Must be driven by bipolar voltage), while the reactive motor can not be so. For example, the four-phase, eight-phase operation (A-AB-B-BC-C-CD-D-DA-A) can be used in two-phase eight-beat mode, and it is not difficult to find that the condition is C =, D =.
A two-phase motor internal winding and four-phase motor exactly the same, low-power motor is generally directly connected to the two-phase, and the power of the motor, in order to facilitate the use of flexible changes in the dynamic characteristics of the motor, often its external wiring for the eight Lead (four-phase), so use, can be used for four-phase motor, can be used for two-phase motor winding or parallel use.
Inductive sub-type stepper motor can be divided into two-phase motor, three-phase motor, four-phase motor, five-phase motor. 17BYG, 86BYG, 110BYG, (international standard), and like 70BYG, 90BYG, 130BYG and so on are the domestic standard. The frame size (motor outside diameter) can be divided into: 42BYG (BYG for the induction sub-stepper motor code)
3, stepper motor static indicators terminology
Number of phases: the number of excitation coils that produce different pairs of N, S magnetic fields. Commonly used m said.
The number of pulses required to complete a periodic change of the magnetic field or the state of the conductivity is indicated by n, or the number of pulses required to turn the motor through a pitch angle. Take the four-phase motor as an example. -BC-CD-DA-AB, four-phase eight-beat operation mode A-AB-B-BC-C-CD-D-DA-A.
Step angle: corresponds to a pulse signal, the motor rotor to turn the angular displacement with θ said. Θ = 360 degrees (rotor teeth J * run the number of beat), to conventional two, four-phase, rotor teeth for the 50 teeth motor as an example. Four-beat running time step angle θ = 360 degrees / (50*4) = 1.88 degrees (commonly known as the whole step), eight beat running time angle θ = 360 degrees / (50*8) = 0.9 degrees Half step).
Positioning torque: the motor in the non-power state, the motor rotor's own locking torque (by the magnetic field tooth profile and mechanical errors caused by)
Static torque: the motor under the rated static electricity, the motor is not rotating movement, the motor shaft locking torque. This torque is a measure of the motor volume (geometry) of the standard, and drive voltage and drive power has nothing to do.
Although the static torque is proportional to the number of turns of the electromagnetic field and is related to the air gap between the stator and rotor, it is not advisable to reduce the air gap and increase the excitation frequency to increase the static moment. This will cause the motor Heat and mechanical noise.
4, stepper motor dynamic indicators and terminology:
1, step angle accuracy:
The error between the actual value of the step motor and the theoretical value. Expressed as a percentage: error / step angle * 100%. Different running beat the value of different, four-beat operation should be within 5%, eight-beat operation should be less than 15%.
2, out of step:
The number of steps running when the motor is running is not equal to the theoretical number of steps. Called out of step.
3, the offset angle:
Rotor tooth axis offset the angle of the stator tooth axis, the motor operation must exist offset angle, the error generated by the offset angle, the use of subdivision drive is not resolved.
4, the maximum no-load start frequency:
Motor in a certain drive form, voltage and rated current, in the case of no load, can directly start the maximum frequency.
5, the maximum no-load operating frequency:
Motor in a certain drive form, voltage and rated current, the motor without load the maximum speed frequency.
6, running torque characteristics:
The curve that the output torque and frequency of the motor is measured under certain test conditions is called the running moment characteristic, which is the most important of many dynamic curves of the motor and the basis of the motor selection. As shown below:
Other features include frequency characteristics, starting frequency characteristics.
Once the motor is selected, the static torque of the motor is determined and the dynamic torque is not the same. The dynamic torque of the motor depends on the average current (not the quiescent current) when the motor is running. The larger the average current, the greater the motor output torque, The harder the frequency characteristics.
Among them, the curve 3 current maximum, or the highest voltage; curve 1 current minimum, or the lowest voltage, curve and load the intersection of the maximum speed point for the load. To make the average current large, as much as possible to improve the drive voltage, so that the use of small inductor high current motor.
7, the resonance point of the motor:
Stepper motor has a fixed resonance area, two, four-phase induction sub-type stepper motor resonance zone is generally between 180-250pps (step angle of 1.8 degrees) or about 400pps (step angle of 0.9 degrees) The higher the motor drive voltage, the greater the motor current, the lighter the load, the smaller the motor volume, the resonance area is shifted upward, and vice versa, in order to make the motor output torque is large, without losing the noise and the whole system, The working point should be offset the resonance area more.
8, the motor is reversing control:
When the motor winding energization timing is AB-BC-CD-DA or () is positive, the power-on sequence is DA-CA-BC-AB or ().
Permanent magnet stepper motor, recommended Shenzhen Zhengdezhi Control Co., Ltd., welcome to consult!