Electrical Signature Analysis
Current Signature Analysis
Bearing Current Analysis
Motor Startup Problems
Electrical Signature Analysis (ESA) evaluates the condition of an electric machine while the asset is operating. When applied to motors or generators, it is sometimes called Motor Current Signature Analysis (MCSA). ESA technologies require the sampling of electrical current in order to gain insight into the condition of the machine and the effect of the load on the machine. ESA tests are used on motors, generators and transformers. ESA tests identify existing issues before they become catastrophic.
Often equipment manufacturers incorporate both ESA and power analysis into one piece of equipment since both can be analyzed from one data acquisition.
Time Domain Analysis
Electrical Signature Analysis time domain data is used to evaluate transient events such as start up issues with motors, drives, soft starts and switchgear. ESA helps resolve load issues such as overloading, cavitation, imbalance, misalignment, etc. ESA is also very useful in process optimization where it is used to maximize the use of an asset without overloading it and causing reliability concerns. And ESA can be used to quickly and easily certify motor operated valves (MOVs) without disassembly.
Frequency Domain Analysis
Electrical Signature Analysis can also be performed very much like vibration and ultrasound analysis when the time domain signal is converted to the frequency domain using a Fast Fourier Transform. In the time domain, it is difficult to evaluate a current signature with its complex combination of frequencies. But, in the frequency domain, the individual frequency components can be identified and correlated to their electrical and mechanical causes. ESA frequencies of interest are typically 20 Hz to about 2 kHz.
ESA frequency analysis requires that the current sample be acquired while the machine has steady state operation for between 10 to 60 seconds (depending on the frequencies of interest). In addition, effective assessment of rotor problems in an induction motor requires a load of at least 40 percent to separate the slip frequency peak from the fundamental line frequency peak.
ESA Complements Vibration and Ultrasound
Many times the issues which are identified with ESA frequency analysis overlap with vibration and ultrasound. ESA has a disadvantage because it is an intrusive technology requiring the opening of an electrical cabinet. But, when it is not possible to directly access a machine such as a submerged pump, ESA becomes an invaluable tool.
What are some of the more common uses for ESA?
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