X20 system modules • Other functions • X20CM4810
X20 system User's Manual 3.10
2113
Imbalance
The term imbalance refers to rotating bodies with a mass that is not rotationally symmetrical. In other words, the
center is not on the axis of rotation
m
u
r
u
S
e
m
s
+ m
u
Ro
tat
ion
of
ax
is
ω
Figure 682: Representative sketch of an imbalance
Imbalance leads to vibrations and increased wear, particularly at high speeds, which is why counterweights are
applied to compensate for this as counterbalance. In practice, it is never possible to fully compensate for this,
meaning each rotating body always has residual imbalance.
The centrifugal force caused by imbalance is dependent on the square speed and thus has a more significant
effect at higher speeds (higher speed frequency). On a spectrum, therefore, the frequency line denoting speed
is significantly higher.
Failure mode
Frequency in the
raw signal spectrum
Frequency in the
envelope spectrum
Comment
Imbalance
1 x fn
-
Only severe imbalance causes peaks in the speed that show up
in the envelope spectrum.
Table 731: Frequency of imbalance
fn
... Nominal speed
The X20CM4810 module can only measure the intensity of the imbalance, not its position on the wave. For this
reason, it cannot be used for balancing.
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