Stepper motors are open-loop controlled motors that convert electrical pulse signals into angular or linear displacements.
Main features of stepper motor:
a. Generally, the accuracy of the stepper motor is 3-5% of the stepping angle, and it is not cumulative;
b. The torque of the stepper motor will decrease with the increase of speed; (Generally, the speed does not exceed 1000 revolutions per minute);
c. The stepper motor can operate normally at low speed, but if it is higher than a certain speed, it cannot be started, accompanied by a whistling sound;
d. The stepper motor has a technical parameter: no-load starting frequency, that is, the pulse frequency of the stepper motor can start normally under no-load conditions, if the pulse frequency is higher than this value, the motor can not start normally, and loss of step or stall may occur.
Stepper motor selection elements:
a. Selection of step angle: The step angle of the motor depends on the requirements of load accuracy, and the minimum resolution (equivalent) of the load is converted to the motor shaft, and how many angles (including deceleration) should be taken by each equivalent motor. The step angle of the motor should be equal to or less than this angle;
b. Selection of static torque: the selection of static torque is based on the load of motor work, and the load can be divided into two types: inertial load and friction load; When starting directly (generally by low speed), both kinds of loads should be considered, inertial loads should be mainly considered when accelerating starting, and frictional loads should be considered when running at constant speed. Under normal circumstances, the static moment should be 2-3 times better than the friction load;
c. Selection of current: motor with the same static torque, due to different current parameters, its operating characteristics are very different, and the current of the motor can be judged according to the torque-frequency characteristic curve.