aims at the problem that the customer calls for "whistling" and "starting pulse" when the motor is running, and it has two definite concepts: the starting frequency of the stepper motor and the no-load start frequency.
Step frequency motor manufacturers to refer to the self starting frequency, because the load with the customer, the size of the load varies widely. Since the start frequency is at a fixed rate (not slowly added frequency) to start the motor, the highest frequency of the motor can start up. For example first, according to 120PPS, if you can, according to 130PPS, if not, you can try 125PPS, if you can, try 126PPS, up from the start, then 125PPS is the frequency of the stepper motor. This parameter can probably explain the stepper motor to start with load capacity start would be more complex, usually deceleration start.
by programming
The stepper motor has a technical parameters: no-load starting frequency is the stepper motor to the normal start of the pulse frequency in the no-load condition, if the pulse frequency is higher than the value of the motor does not start, you may lose steps or stall occurs. In the case of load, the starting frequency should be lower. If the motor is to rotate at high speed, the pulse frequency should have an acceleration process, that is, the starting frequency is low, and then a certain acceleration to the desired high frequency (motor speed from low speed to high speed).

In addition to the above reasons, noise may be due to excessive load caused by the high speed when the output torque of the motor will decline, unable to meet the load requirements of the motor blockage, and Howling will change with the change of the height of the frequency, the solution is to reduce speed or torque motor to replace the more. In addition, the motor will stop short after high speed operation, which is caused by chopping the phase current. It only needs to set the automatic half flow on the driver panel to be valid.