One of the stepper motor's technical parameters is: no-load starting frequency

       If the pulse frequency is higher than this value, the stepping motor will not start normally, and the lost or blocked phenomenon may occur.

       The stepping motor should have a lower starting frequency under load. If the stepping motor is to be operated at high speed, the pulse frequency should be set with acceleration and deceleration time, that is, the starting frequency is low, and then raised to the set maximum frequency according to a certain acceleration time (the stepping motor speed is increased from low speed to high speed).

       Stepper motor can not be started at high speed except for the above reasons, the whistling sound may be caused by excessive load and the output torque of the stepping motor will decrease when the motor is running at high speed, and the stepping motor will be blocked if the load requirement can not be met. And the howling sound changes with the frequency change and the solution is to reduce the stepping motor speed or replace the stepping motor with larger static torque.