Vibration monitoring
Vibration measurement is at the heart of the monitoring of rotating machines. Although electrical machines are generally low-vibration devices, they may be coupled to high-vibration prime movers or driven plant via flexible couplings and mounted on separate foundations via resilient mounts. The excitation of electrical machine vibration is generally mechanical unbalance or harmonic electromagnetic forces originating from the machine airgap. The response of the machine to these exciting forces depends on the precise coupling and mounting of the machine. Vibration monitoring and shock pulse analysis are non-invasive but use a number of specialised sensors, broad bandwidth and complex analysis. The precise selection and location of sensors is very important. However, because of its wide application in other rotating machines vibration analysis has established itself as a reliable and widely accepted technique for electrical machines and shock pulse analysis, and also (particularly for bearings) because it is capable of differentiating between mechanical and electromagnetic excitation forces, which is invaluable in detecting root causes before they develop into failure modes. Motor speed has been analysed using instantaneous angular speed to detect rotor electrical faults but has not been widely used by operators. This chapter shows the close relationship between vibration and electrical monitoring of the machine.
Vibration monitoring, Page 1 of 2
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