IEC TS 60034-32 pdf free download
IEC TS 60034-32 pdf free download.Rotating electrical machines – Part 32: Measurement of stator end-winding vibration at form-wound windings.
4Causes and effects of stator end-winding vibrations
Thephysical background of stator end-windingvibration is described in AnnexA
The predominant cause for stator end-winding vibration is the force-distribution due to the
electromagnetic field in the active part and the machine’s end-winding region.These forces
depend on operational parametersactive power,reactive power) and are generally
unavoidable.They are dominatedby twice the fundamental frequency of phase currents,i.e
100 Hz if operating at 50 Hz grid and 120 Hz if operating at 60 Hz grid.
Global and local aspects of stator end-winding vibrations are generally distinguished: a global
vibration involves a large part of stator end-winding structurei.e.he winding bars outside the
stator core and the support components.Local vibration involves only a part of the stator end-
winding structure with typically small spatial extension relative to the circumference of the
stator end-winding.Localvibration modes can always be excited during operation.On the
other hand,gbaimodes are not always excited,evniftheir natural frequency
matches the frequency of electromagnetic force-excitation.A global vibration mode can
generally lead to significant operational vibration levels,if the mode-shape of a 2-pole
machine exhibits 4 nodes or if the mode-shape of a 4-pole machine exhibits 8 nodes.In some
cases,even for 4poles.the4-node mode can induce a significant operational vibration level
e.g.in case of fractional slot winding).Another force that may lead to end-winding vibration is
due to rotor vibration at one times the rotational speed (1x).The rotor vibration through the
bearings may couple to the stator frame and core,and hen to the end-winding.
Although the vibration excitation is due to a rotating electromagnetic field inside the machine
the vibration amplitude is generally not constant along the circumference of the stator end-
windingA sufficient number of equidistantly distributed sensors is required to estimate the
maximum of global vibration
Stator end-winding vibration levels may change over time due to operational parameter
changes,as active power,eactivepowr,volage,operational temperature.Operation
parameters of the electric machine should be recorded in parallel with vibration data and be
available for analysis.Apart from this,long-term changes of the stator end-windingvibration
level at comparable operational parameters could indicate a change in structural dynamics,
which typically results in gradually decreasing natural frequencies of the relevant vibration
modes.The detection of such long-term changes is the main purpose of the vibration
trending.Sudden changes of the monitored vibration amplitudes after electrical faults could
also be an indicator for a changed stator end-winding structure and can be irreversible
Specific frequency or vibration limits are not part of this document.It should be pointed out
that changes in the monitored vibration are likely to be of greater significance than the actual
magnitude of such values (for more detailed information,see 7.2).For the time being,if
acceptance or operational monitoring vibration criteria are required they should be based on
experience with a particular class and type of machine -if such experience exists -and
agreed on a caseby case basisbetween the customer and manufacturer.
NOTE This is because the vibration is very much dependent on the specific design features of a particular electrical machine, for example stator end-winding designs differ a lot between air cooled, hydrogen cooled and water cooled generators and between different manufacturers. For HV motors the variation of the end winding design depends on the specific application. Therefore it is not possible to apply a universal set of limits which can be applied to even nominally similar types of machines from different manufacturers. Furthermore, currently there is only a small amount of data available and this is insufficient to define internationally accepted vibration criteria for acceptance or operational monitoring.IEC TS 60034-32 pdf download.
