Stepping Motor and its selection

by:V&T Technologies     2020-01-19
Stepping Motor and its selection. Stepping motor is also called Stepping Motor. The name is different. Don't panic. Stepping motor is stepping motor. Today, stepping motor manufacturers will show you the common sense of selecting stepping motor, I hope it will be helpful for everyone to choose stepping motors. There are too many stepping motors and different models have different uses. I hope it will be helpful for everyone to choose stepping motors. Stepping Motor construction: by rotor ( Rotor iron core, permanent magnet, rotating shaft, ball bearing), Stator (Winding, stator core), Front and rear end covers, etc. The stator of the most typical two-phase Hybrid Stepping Motor has 8 large teeth, 40 small teeth and 50 small teeth; The stator of the three-phase motor has 9 large teeth, 45 small teeth and the rotor has 50 small teeth. Main parameters of stepping motor: phase number: refers to the number of coil groups inside the motor. Currently, two-phase, three-phase and five-phase stepping motors are commonly used. Number of Beats: The number of pulses or conductive state required to complete a periodic change of magnetic field, expressed by m, or the number of pulses required for the motor to turn over a pitch angle. Holding torque: refers to the torque that the stator locks the rotor when the stepping motor is energized but not rotated. Step angle: corresponding to a pulse signal, the angular displacement of the motor rotor. Positioning torque: the locking torque of the motor rotor itself when the motor is not energized. Out of Step: The number of steps running when the motor is running is not equal to the theoretical number of steps. Offset angle: the angle at which the rotor tooth axis is offset from the stator tooth axis. There must be an offset angle when the motor is running. The error caused by the offset angle cannot be solved by subdivision drive. Operating moment-frequency characteristics: the curve of the relationship between output torque and frequency during Operation measured by the motor under certain test conditions. The characteristics of stepping motors, the general precision of stepping motors is 3-5%, and does not accumulate; The maximum allowable temperature of the stepping motor surface depends on the demagnetization points of different motor magnetic materials; The torque of the stepping motor will decrease with the increase of the rotating speed (U = e l (di/dt)I * R) No-load starting frequency: that is, the pulse frequency that the stepping motor can start normally under no-load condition. If the pulse frequency is higher than this value, the motor cannot start normally, and step loss or locked rotation may occur. The starting speed of stepping motor is generally 10 ~ 100 RPM, the starting speed of servo motor is generally 100 ~ 300 RPM. Depending on the size and load of the motor, the large motor generally corresponds to a lower starting speed. Low frequency vibration characteristics: the stepping motor moves while running repeatedly in a continuous step distance state. The movement of its step state produces a 1-step response. Where: Zr is the number of rotor teeth; Tk is the motor load torque; J is the rotation penetration of the rotor. The relationship between voltage and current and rotation speed and torque. When the stepping motor is constant, the voltage value supplied to the driver has a great influence on the performance of the motor. The higher the voltage, the greater the torque that the stepping motor can generate, the more convenient it is for occasions requiring high-speed application, but the heating of the motor increases with the increase of voltage and current, so it should be noted that the temperature of the motor cannot exceed the maximum limit. Select principle 1. First, determine the torque required by the stepping motor to drag the load. The simplest method is to add a lever to the load shaft and pull the lever with a spring balance. The pulling force multiplied by the length of the Force arm is both the load torque. Or calculated theoretically according to the load characteristics. Since the stepping motor is a control motor, the maximum torque of the commonly used stepping motor is not more than 45Nm. The larger the torque, the higher the cost. If the motor torque you choose is larger or exceeds this range, you can consider adding a deceleration device. 2. Determine the maximum running speed of the stepping motor. The speed index is very important in the selection of stepping motor. The characteristic of stepping motor is that the torque decreases with the increase of motor speed. The speed of decrease is related to many parameters, such: the driving voltage of the driver, the phase current of the motor, the phase inductance of the motor, the size of the motor, etc. , the general rule is: the higher the driving voltage, the slower the torque drop; The larger the phase current of the motor, the slower the torque drop. In the design scheme, the rotating speed of the motor should be controlled within 600 rpm or 800 rpm. Of course, this is not standard. Please refer to moment-Frequency characteristics 〉. 3. According to the two important indexes of load maximum torque and maximum rotation speed, refer to moment- Frequency characteristics>, you can choose a suitable stepping motor. If you think that the motor you choose is too large, you can consider adding a speed reducer, which can save costs and make your design more flexible. To choose the appropriate reduction ratio, we should comprehensively consider the relationship between torque and speed and choose the best scheme. 4. Finally, we must consider leaving a certain amount (Such as 50%)Torque margin and speed margin. 5. Hybrid stepping motor can be selected first, and reactive stepping motor can be selected if due to price factors. 6. Try to select the subdivision step driver and make the driver work in the subdivision state. 7. When selecting, don't go into the misunderstanding of only looking at the torque of the motor, that is to say, the larger the torque of the motor, the better, and consider it together with the speed index. 8. The ultra-small driver and the micro-driver use the shell as the radiator and should be fixed on a larger and thicker metal plate or an external fan to dissipate heat. If there is no heat dissipation condition, and the driver works at a lower speed (At this time, the drive is hot) Can be replaced by a 90-type driver with a fan. TAG stepping, stepping motor, motor, stepping motor selection, motor selection, stepping motor, selection
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