SLVAES8 May   2020 DRV8424 , DRV8424E , DRV8426 , DRV8428 , DRV8428E , DRV8434 , DRV8434E , DRV8434S , DRV8436 , DRV8436E , DRV8889-Q1

 

  1.   How to Reduce Audible Noise in Stepper Motors
    1.     Trademarks
    2. 1 Introduction
    3. 2 Details of the Test Setup
    4. 3 Sources of Noise in a Stepper Motor
      1. 3.1 Magnetic Noise
      2. 3.2 Mechanical Noise
      3. 3.3 Electrical Noise
        1. 3.3.1 Effects of Current Ripple and Decay Mode
        2. 3.3.2 Effects of PWM Chopper Frequency
        3. 3.3.3 Effects of Current Zero-cross Error
        4. 3.3.4 Effects of Step Resolution and Step Frequency
        5. 3.3.5 Effects of Resonant Frequency
    5. 4 Summary
    6. 5 References

3.2 Mechanical Noise

Mechanical noise is caused by the physical components in the structure of the stepper motor. Common examples contributing to noise include unsecured mounting structures, bent shafts, and loose or no bearings. All of these examples cause unnecessary vibrations and resonant frequencies to appear. Other mechanical noise factors include motor housing, balance of rotor, and bearing choice.

The motor housing structure has a significant effect on high speed motor applications. If the rotor is out of balance, there will be a spike in frequency directly related to speed of the motor. Electric motors use serval types of bearings: sliding sleeve bearings or rolling bearings. Sleeve bearings are generally considered to be quiet bearings. A properly lubricated sleeve bearing will only produce very high noise frequencies due to the bearing and shaft finish. Rolling bearings are generally considered to be noisy and have many factors that could lead to a noisy outcome.

Most mechanical noise can be minimized by stiffening the mounting structures and choosing noise dampening materials - such as mounting the motors in sound absorbing materials like rubber, balancing the rotor, and using properly maintained bearings.