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一、Stepper motor selection method
There are step angle stepping motor (related to the number of phases), holding torque, the current composition of the three elements. Determine these three elements will be able to determine the stepper motor model.
1、Step angle selection
Motor step angle accuracy depends on the load requirements, the load of a minimum resolution (equivalent) converted to the motor shaft, the motor should take each equivalent number of angles (including gear), motor step angle should be equal to or less than this angle. Permanent magnet stepper motor is generally two-phase (bipolar) and four phase (unipolar), step angle is generally 3.6 degrees 7.5 degrees, 15 degrees, 18 degrees, 7.5 degrees among the most common; hybrid step into the motor is divided into two phases, phase and five phase: two-phase step angle of 1.8 degrees and 0.9 degrees, three-phase step angle of 1.2 degrees while the general five-phase step angle of 0.72 degrees. Reaction is generally three-phase stepper motor, step angle is generally 1.5 degrees, but the noise and vibration are great. In Europe and other developed countries, the 1980s have been eliminated.
2、The choice of holding torque
The dynamic torque stepper motor is difficult to determine at once, we tend to make sure the motor holding torque. Holding torque selection is based on the work load of the motor and the load inertia load and friction can be divided into two kinds of loads. Single inertia load and a single friction load does not exist. Direct start (generally low) when the two kinds of loads are to be considered, the main consideration when starting acceleration inertia load, constant speed operation as long as consideration friction loads. Under normal circumstances, the friction load holding torque should be 2-3 times as well, holding torque Once selected, the motor is able to determine the length of the base and down (geometry).
3、Current selection
Like holding torque of the motor, the current parameters are different, their operating characteristics vary widely, the general current of 0.5A or less applicable to 300RPM or less, current 1A above applies to 300RPM or more.
4、Torque and Power Conversion
Stepper motors are generally used in a wide range of speed, its power is changing, generally used to measure torque, torque and power conversion is as follows:
P= Ω·M
Ω=2π·n/60
P=2πnM/60
Of P is the power in watts, Ω is the angular velocity per second, in units of radians, n is the rotational speed per minute, M is the torque in units of Newton meters
P = 2πfM/400 (1.8 degree motor half-step work)
Where f is the number of pulses per second (abbreviated PPS)
二、Stepper motor applications Precautions
1, the stepper motor used in low-speed situations - RPM does not exceed 1000 rpm, preferably between 150-450RPM use, can make it through the deceleration devices work here, then the motor, high efficiency, low noise.
2, the stepper motor is best not to use the state of the whole step, whole step state vibration.
3, due to historical reasons, only a nominal voltage of 12V with 12V motor, other than the motor drive voltage V voltage value, according to the drive select driving voltage (recommended: 42 Motor DC 12V-24V, 57 DC motors 24-36V), of course, in addition to 12 volts 12V constant voltage drive outside can also use other drive power, but to consider the temperature rise.
4, the moment of inertia of the load should be chosen larger frame size motor.
5, the motor in a relatively high speed or high inertia load, the working speed is generally not start, and the frequency of a gradual rise speed, an electric motor without losing step, the second noise can be reduced while improving the accuracy of the positioning stop.
6, high-precision, should be through mechanical reduction, increased motor speed or number of segments with high drive to solve, you can use 5-phase motors.
7, the region of the vibration motor not working, should be available by changing the voltage, current, or add some damping solution.
8, the motor 90RPM following work should be a small current, a large inductance, low voltage to drive.
9, to be followed after the election before the election motor drive principle.
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