The basic characteristics of a stepper motor include the static characteristics of the motor
2020年2月27日The basic characteristics of a stepper motor include the static characteristics of the motor, successive motion characteristics (dynamic characteristics), motor starting characteristics, and motor braking characteristics (transient characteristics). The following are introduced separately: Static torque characteristics When the coil of the stepping motor is DC, the electromagnetic torque of the rotor with a load (the rehabilitation electromagnetic torque that occurs when it is balanced with the load torque is called static torque or stop torque) and the rotor The connection of the power angle is called the viewpoint-stop torque characteristic, which is the static characteristic of the motor. Because the rotor is a permanent magnet, the air gap magnetic density that emerges is sinusoidal, so theoretically the stopping torque curve is a sine wave.
This viewpoint-stop torque characteristic is an important indicator of the electromagnetic torque capability of a stepper motor. The larger the maximum torque, the better, and the closer the torque waveform to the sine, the better. In fact, there is cogging torque under the magnetic poles, which causes the distortion of the combined torque. For example, the cogging torque of a two-phase motor is 4 times the harmonic of the viewpoint period of the stop torque and is added to the sinusoidal stop torque. The torque shown is: TL = TMsin [(θL / θM) π; / 2] TL and TM each indicate the load torque and the maximum stopping torque (or holding torque), and the corresponding power angle is θL And θM, the change of this displacement angle determines the azimuth accuracy of the stepper motor. According to the above formula: θL = (2θM / π;) arcsin (TL / TM) The step angle θs of PM type permanent magnet stepper motor and HB hybrid stepper motor was mentioned in the previous course: θs = 180 \u0026 deg ; / PNr, the viewpoint is changed to the mechanical viewpoint (radian), then becomes the following formula: θs = π; / (2Nr) The above formula Nr is the number of rotor teeth or pole pairs, so two-phase motor θM = θs. The load torque is the load of the electromagnetic torque (such as the spring force or the lifting force of a heavy object).
If the motor is to move forward and backward, a viewpoint error of 2θL will occur. To improve the azimuth accuracy, θL will be small. Therefore, According to the formula θL = (2θM / π;) arcsin (TL / TM), a stepping motor with a large maximum stopping torque Tm and a small step angle θs, that is, a high-resolution motor, should be selected. According to the formula θs = π; / (2Nr), it can be known that the smaller θs is, the larger Nr is, the better. In addition, the rotor structure of high-resolution stepper motors is roughly divided into three types: PM type, R type, and HB type, among which HB type has the best resolution. Because of the connection of PM type stator poles with claw-level structure, the addition of stator poles is restricted by machining. The HB type rotor has no teeth on the surface. The N and S poles are replaced with magnets on the surface of the rotor. Therefore, the number of poles is the number of pole pairs Nr. Similarly, the addition of the rotor poles Nr is also restricted by the magnetizing machinery. When the number of teeth of the R-type rotor is the same as that of the HB-type, because permanent magnets are not used, although the same Nr is used, the step angle θs is twice that of the HB-type, and because there is no permanent magnet pole, the maximum torque Tm is smaller than the HB-type.两 When the outer diameter of the two-phase stepping motor is about 42mm, Nr = 100 teeth, the step angle is 0.9 \u0026 deg ;, which is the highest resolution in practical applications. As Nr becomes larger and reactance is added, the torque decreases at high speeds. Therefore, the motor with Nr = 50 and step angle of 1.8 \u0026 deg; is widely used. For the HB structure, the step angle accuracy in the full step state is ± 3%. The stepper motor operation point of view θ = nθs. There is no cumulative error in each step of the operation. If the speed of the motor is large enough, try to improve n (θs as small as possible) ) To improve azimuth positioning accuracy. Dynamic torque characteristics Dynamic torque characteristics include driving pulse frequency-torque characteristics and driving pulse frequency-inertia characteristics. Pulse frequency-torque characteristic Pulse frequency-torque characteristic is an important characteristic for selecting a stepping motor. The vertical axis is the dynamic torque (dynamictorque), and the horizontal axis is the response pulse frequency. The response pulse frequency is expressed in pps (pulsepersecond), which is the number of pulses per second. As shown in the figure, the dynamic torque onset of a stepper motor includes two torques, pull-out-torque and pull-in-torque. The former is called out-of-step or lost torque, and the latter is called starting or pull-in torque.
The pull-in torque scale ranges from zero to the maximum self-starting pulse frequency or the maximum self-starting frequency. The area enclosed by the pull-in curve is called the self-starting area. The motor performs synchronous forward and reverse starting operation. The running area is between the pull-in and out-of-step areas. The motor can run with the corresponding load in this area. The load torque beyond the scale will not be able to run in succession, and the out-of-step phenomenon will appear. . The stepping motor is controlled by an open-loop drive. There must Range hood motor factory https://www.chinakxdq.com/product/range-hood-motor-integrated-stove-motor/ be a margin between the load torque and the electromagnetic torque, and its value should be 50% ~ 80%. Out-of-step torque is equal to pull-in torque at 0pps. With the increase of the control pulse frequency, the load can decrease. At the beginning of the operation, the control pulse frequency should be added slowly in order to use the large torque at low speed to supply the acceleration torque required by the motor at low speed operation to reduce the acceleration time. The smaller the inductance of the stator coil of the stepper motor is, the larger the maximum response pulse frequency is, so that the slow acceleration driving can be changed to the fast acceleration driving operation. Pulse frequency-inertia characteristics When stepping motors start quickly with inertia load, they must have sufficient starting acceleration. Therefore, if the inertia of the load is added, the starting pulse frequency will decrease. For this reason, the two must be summarized and considered when selecting a stepper motor. In the figure below, the vertical axis is the maximum self-starting frequency, and the horizontal axis is the load inertia. The curve shows the relationship between the load inertia and the maximum self-starting pulse frequency. Here take PM type claw pole stepping motor (two-phase, step angle 7.5 \u0026 deg;) as an example. Under load PL, the relationship between the maximum self-starting pulse frequency PL and the load inertia Jc is as follows: In the formula, the JR stepper motor rotor inertia, Ps is the maximum self-starting frequency at no load.
This viewpoint-stop torque characteristic is an important indicator of the electromagnetic torque capability of a stepper motor. The larger the maximum torque, the better, and the closer the torque waveform to the sine, the better. In fact, there is cogging torque under the magnetic poles, which causes the distortion of the combined torque. For example, the cogging torque of a two-phase motor is 4 times the harmonic of the viewpoint period of the stop torque and is added to the sinusoidal stop torque. The torque shown is: TL = TMsin [(θL / θM) π; / 2] TL and TM each indicate the load torque and the maximum stopping torque (or holding torque), and the corresponding power angle is θL And θM, the change of this displacement angle determines the azimuth accuracy of the stepper motor. According to the above formula: θL = (2θM / π;) arcsin (TL / TM) The step angle θs of PM type permanent magnet stepper motor and HB hybrid stepper motor was mentioned in the previous course: θs = 180 \u0026 deg ; / PNr, the viewpoint is changed to the mechanical viewpoint (radian), then becomes the following formula: θs = π; / (2Nr) The above formula Nr is the number of rotor teeth or pole pairs, so two-phase motor θM = θs. The load torque is the load of the electromagnetic torque (such as the spring force or the lifting force of a heavy object).
If the motor is to move forward and backward, a viewpoint error of 2θL will occur. To improve the azimuth accuracy, θL will be small. Therefore, According to the formula θL = (2θM / π;) arcsin (TL / TM), a stepping motor with a large maximum stopping torque Tm and a small step angle θs, that is, a high-resolution motor, should be selected. According to the formula θs = π; / (2Nr), it can be known that the smaller θs is, the larger Nr is, the better. In addition, the rotor structure of high-resolution stepper motors is roughly divided into three types: PM type, R type, and HB type, among which HB type has the best resolution. Because of the connection of PM type stator poles with claw-level structure, the addition of stator poles is restricted by machining. The HB type rotor has no teeth on the surface. The N and S poles are replaced with magnets on the surface of the rotor. Therefore, the number of poles is the number of pole pairs Nr. Similarly, the addition of the rotor poles Nr is also restricted by the magnetizing machinery. When the number of teeth of the R-type rotor is the same as that of the HB-type, because permanent magnets are not used, although the same Nr is used, the step angle θs is twice that of the HB-type, and because there is no permanent magnet pole, the maximum torque Tm is smaller than the HB-type.两 When the outer diameter of the two-phase stepping motor is about 42mm, Nr = 100 teeth, the step angle is 0.9 \u0026 deg ;, which is the highest resolution in practical applications. As Nr becomes larger and reactance is added, the torque decreases at high speeds. Therefore, the motor with Nr = 50 and step angle of 1.8 \u0026 deg; is widely used. For the HB structure, the step angle accuracy in the full step state is ± 3%. The stepper motor operation point of view θ = nθs. There is no cumulative error in each step of the operation. If the speed of the motor is large enough, try to improve n (θs as small as possible) ) To improve azimuth positioning accuracy. Dynamic torque characteristics Dynamic torque characteristics include driving pulse frequency-torque characteristics and driving pulse frequency-inertia characteristics. Pulse frequency-torque characteristic Pulse frequency-torque characteristic is an important characteristic for selecting a stepping motor. The vertical axis is the dynamic torque (dynamictorque), and the horizontal axis is the response pulse frequency. The response pulse frequency is expressed in pps (pulsepersecond), which is the number of pulses per second. As shown in the figure, the dynamic torque onset of a stepper motor includes two torques, pull-out-torque and pull-in-torque. The former is called out-of-step or lost torque, and the latter is called starting or pull-in torque.
The pull-in torque scale ranges from zero to the maximum self-starting pulse frequency or the maximum self-starting frequency. The area enclosed by the pull-in curve is called the self-starting area. The motor performs synchronous forward and reverse starting operation. The running area is between the pull-in and out-of-step areas. The motor can run with the corresponding load in this area. The load torque beyond the scale will not be able to run in succession, and the out-of-step phenomenon will appear. . The stepping motor is controlled by an open-loop drive. There must Range hood motor factory https://www.chinakxdq.com/product/range-hood-motor-integrated-stove-motor/ be a margin between the load torque and the electromagnetic torque, and its value should be 50% ~ 80%. Out-of-step torque is equal to pull-in torque at 0pps. With the increase of the control pulse frequency, the load can decrease. At the beginning of the operation, the control pulse frequency should be added slowly in order to use the large torque at low speed to supply the acceleration torque required by the motor at low speed operation to reduce the acceleration time. The smaller the inductance of the stator coil of the stepper motor is, the larger the maximum response pulse frequency is, so that the slow acceleration driving can be changed to the fast acceleration driving operation. Pulse frequency-inertia characteristics When stepping motors start quickly with inertia load, they must have sufficient starting acceleration. Therefore, if the inertia of the load is added, the starting pulse frequency will decrease. For this reason, the two must be summarized and considered when selecting a stepper motor. In the figure below, the vertical axis is the maximum self-starting frequency, and the horizontal axis is the load inertia. The curve shows the relationship between the load inertia and the maximum self-starting pulse frequency. Here take PM type claw pole stepping motor (two-phase, step angle 7.5 \u0026 deg;) as an example. Under load PL, the relationship between the maximum self-starting pulse frequency PL and the load inertia Jc is as follows: In the formula, the JR stepper motor rotor inertia, Ps is the maximum self-starting frequency at no load.
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