Noise analysis of DC motor:

1. Bearing noise. Due to improper size of bearing and bearing cavity, DC motor will rotate with DC motor rotor and generate noise. The out of roundness of the ball or the internal mixing of the debris will cause them to bump against each other and produce vibration and noise. Improper bearing preload will cause slight vibration and noise on the raceway surface.

2. Noise caused by rotor imbalance.

3. Noise caused by eccentric assembly.

The following methods shall be adopted to reduce the noise of DC motor:

1. Pay attention to avoid the resonance frequency of the motor;

2. Sine winding shall be used as far as possible to reduce harmonic components.

3. Rotor chute with one stator slot pitch;

4. The magnetic circuits of stator and rotor are symmetrical and average, with close overlap.

5. Select appropriate grooves together to prevent low order force waves;

Source: Jiangmen vacuum cleaner manufacturer www.jmchiyang.com