A stepper motor is an actuator that converts electrical pulses into angular displacement. To put it bluntly: when the stepper driver receives a pulse signal, it drives the stepper motor to rotate a fixed angle (and step angle) in the set direction. You can control the angular displacement by controlling the number of pulses to achieve accurate positioning. At the same time, you can control the speed and acceleration of the motor by controlling the pulse frequency to achieve the purpose of speed regulation.
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   2. What are the types of stepper motors ?
   There are three types of stepping motors: permanent magnet ( PM ) , reactive ( VR ) and hybrid ( HB ).
   The permanent magnet stepping is generally two-phase, the torque and the volume are small, and the step angle is generally 7.5 degrees or 15 degrees;
   The reactive stepping is generally three-phase, which can achieve high torque output. The step angle is generally 1.5 degrees, but the noise and vibration are very large. 80 years have been eliminated in Europe and other developed countries; hybrid stepper mean the combination of the advantages of permanent magnet and reactive. It is divided into two phases and five phases: the two-phase step angle is generally 1.8 degrees and the five-phase step angle is generally 0.72 degrees. This stepper motor is the most widely used.
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   3. What is the holding torque ( HOLDING TORQUE ) ?
   The holding torque ( HOLDING TORQUE ) is the moment at which the stator locks the rotor when the stepping motor is energized but not rotating. It is one of the most important parameters of a stepper motor. Usually, the torque of the stepper motor at low speed is close to the holding torque. Since the output torque of the stepping motor is continuously attenuated as the speed increases, the output power also changes with the increase of the speed, so the holding torque becomes one of the most important parameters for measuring the stepping motor. For example, when people say that a 2N.m stepper motor, unless otherwise specified, is a stepper motor that maintains a torque of 2N.m.
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   4. What is DETENT TORQUE?
   DETENT TORQUE is the torque at which the stator locks the rotor when the stepper motor is not energized.
   DETENT TORQUE does not have a unified translation method in China, which is easy to misunderstand. Because the rotor of reactive stepper motor is not permanent magnet material, it does not have DETENT TORQUE .
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   5. What is the accuracy of the stepper motor? Do you accumulate ?
   The accuracy of a general stepper motor is 3-5% of the step angle and does not accumulate.
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   6. What is the allowable temperature of the stepper motor ?
   If the temperature of the stepping motor is too high, the magnetic material of the motor will be demagnetized firstly, resulting in a torque drop and even out of step. Therefore, the maximum allowable temperature of the motor surface should depend on the demagnetization point of the magnetic material of different motors; in general, the demagnetization of the magnetic material The points are all above 130 degrees Celsius , and some even up to 200 degrees Celsius , so the external temperature of the stepper motor is completely normal at 80-90 degrees Celsius .
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   7. Why does the torque of the stepper motor decrease with increasing speed ?
   When the stepper motor rotates, the inductance of each phase winding of the motor will form a back electromotive force; the higher the frequency, the larger the back electromotive force. Under its action, the motor decreases with increasing frequency (or speed), resulting in a drop in torque.
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   8. Why the stepping motor can run normally at low speed , but if it is higher than a certain speed, it can't start , accompanied by howling ?
   The stepping motor has a technical parameter: the no-load starting frequency, that is, the pulse frequency that the stepping motor can start normally under no-load conditions. If the pulse frequency is higher than this value, the motor cannot start normally, and lost or blocked may occur. In the case of load, the starting frequency should be lower. If the motor is to be rotated at a high speed, the pulse frequency should have an acceleration process, that is, the starting frequency is low, and then rise to a desired high frequency (the motor speed is increased from a low speed to a high speed) at a certain acceleration.
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   9. How to overcome the vibration and noise of the two-phase hybrid stepping motor at low speed ?
   The large vibration and noise of the stepping motor at low speed is its inherent shortcoming. Generally, the following solutions can be used to overcome:
   A. If the stepper motor works just in the resonance zone, the resonance zone can be avoided by changing the gear ratio and other mechanical transmissions;
   B. Using a drive with subdivision, this is the most common and easiest method;
   C. Change to a stepper motor with a smaller step angle, such as a three-phase or five-phase stepper motor;
   D. Switching to AC servo motor can almost completely overcome vibration and noise, but the cost is higher;
   E. A magnetic damper is added to the motor shaft. This product is available on the market, but the mechanical structure changes greatly.
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   10. Does the number of subdivisions of the subdivision drive represent accuracy ?
   The subdivision technology of the stepping motor is essentially an electronic damping technology (please refer to the relevant literature). Its main purpose is to reduce or eliminate the low frequency vibration of the stepping motor, and improve the running accuracy of the motor is only a supplementary function of the subdivision technology. For example, for a two-phase hybrid stepping motor with a step angle of 1.8 ° , if the subdivision number of the subdivision driver is set to 4 , then the motor's operating resolution is 0.45 ° per pulse , and the accuracy of the motor can be reached or approached. 0.45 °, also depends on other factors such as the subdivision current control accuracy of the subdivision driver. The accuracy of subdivision drivers from different manufacturers may vary greatly; the larger the number of subdivisions, the more difficult it is to control.
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   11. What is the difference between the series connection method and the parallel connection method of the four-phase hybrid stepping motor and the driver ?
   The four-phase hybrid stepping motor is generally driven by a two-phase driver. Therefore, the four-phase motor can be connected to two phases by series connection or parallel connection. The series connection method is generally used in the case where the motor speed is relatively high. At this time, the required output current of the driver is 0.7 times of the motor phase current , so the motor generates little heat; and the connection method is generally used in the case where the motor speed is high (also called high speed connection method). ), the required driver output current is 1.4 times the motor phase current , so the motor generates a large amount of heat.
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   12. How to determine the DC power supply of the stepper motor driver ?
   A. Determination of voltage: The power supply voltage of the hybrid stepping motor driver is generally a wide range (for example , the power supply voltage of the IM483 is 12 to 48 VDC ), and the power supply voltage is usually selected according to the operating speed and response requirements of the motor. If the motor has a higher operating speed or a faster response, the voltage is also higher, but note that the ripple of the supply voltage cannot exceed the maximum input voltage of the drive, otherwise the drive may be damaged.
   B. Determination of current: The supply current is generally determined by the output phase current I of the driver . If the linear power supply current is generally preferably 1.1 to 1.3 times I; if switching power supply current is generally preferably 1.5 to 2.0 times of I.
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   13. Under what circumstances is the offline signal FREE of the hybrid stepper motor driver used ?
   When the offline signal FREE is low, the current output from the driver to the motor is cut off, and the motor rotor is in a free state (offline state). In some automation equipment, if the motor shaft (manual mode) is required to be directly powered while the drive is uninterrupted, the FREE signal can be set low, the motor can be taken offline, and manually operated or adjusted. After manual completion, set the FREE signal high to continue automatic control.
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   14. If you use a simple method to adjust the direction of rotation of the two-phase stepper motor after power-on ?
   Simply swap the motor and driver wiring A+ and A- (or B+ and B- ).
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