*3.4.3. Load induced noise*

216 Induction Motors – Modelling and Control

The main mechanical sources of the noise

 Number of rolling elements carrying the load Mechanical resonance frequency of the outer ring

rotational speed changes from ��to�� can be expressed as

��� <sup>=</sup> �� �

��� <sup>=</sup> �� �

Inaccurate machining of parts

machine.

Alignment

Running speed

Temperature

Where

Lubrication conditions

Ball pass frequency – outer race


*3.4.2. Sleeve bearings* 


k=1, 2, 3, …


��…number of groove

*3.4.1. Rolling bearings* 

movement of the whole system and thus increasing vibration and noise of the electric

The noise of rolling bearings depends on the type of bearing and its construction and accuracy of bearing parts. The increase in vibration and noise level of bearings, when the

��� = ��� ��� ��

� ��� �� � ��

� ��� �� � ��

��

(27)

� � ����� (28)

� � ����� (29)

��� = �� �� (30)

��� = ��� �� (31)

In certain cases, the vibrations and thus noise transmitted from the load, which is connected to the induction motor. In most cases, this occurs with wrong balance or bad connects of couplings. Uneven distribution load acting on the motor shaft or inappropriate use of gears may also affect noise machine. The only possible protection against these effects is the perfect balance of the whole set and if possible an even distribution of forces acting on the connecting elements. Noise arises too due to coupling of the machine with a load, e.g., shaft misalignment. Next noise arises from belt transmission, from cogwheels and couplings. It may also arise to noise due to mounting the machine on foundation or other structure.
