Electrical Signature Analysis Series – Part 1

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In this lecture series, we will be discussing Electrical Signature Analysis (ESA), which is a method for evaluating electrical machinery while energized. The topic will be quite broad and is to include an analysis of supply power through the driven load.

While we will rely upon some of our previous discussions to provide information and definitions for some of our new information, we will start this series by providing some definitions unique to ESA:

  • Voltage: Electrical pressure, is also termed as electromotive force. Voltage is generated.
  • Current: Defined in classical physics as electron flow. Current is demanded in order to produce work and is a result of the load.
  • Upstream/Downstream: Upstream refers to the electrical system in the direction of generation or distribution from the point of test. Downstream is towards the motor and load from the point of test.
  • FFT: Fast Fourier Transform (FFT) is a mathematical method of separating the frequencies of a ‘sine wave’ and presenting them as frequencies and amplitude.
  • Spectra: Is the graph of frequencies and amplitudes resulting from an FFT.
  • Voltage and Current FFT: Spectra of voltage and current.
  • Motor Current Signature Analysis (MCSA): A method of viewing demodulated current and current FFT’s to evaluate the condition of machinery downstream of the point being tested.
  • Voltage Signature Analysis (VSA): A method of viewing voltage FFT’s to evaluate the condition of machinery upstream of the point being tested.
  • Torsional Analysis (TA): A method of viewing the current resulting from the load and its torsional effect (pulsating loads, etc.).
  • Inrush Analysis: A method of viewing the inrush effects on voltage and current when electrical machinery is started.
  • Power Quality: The industry has defined this as reviewing voltage and current. Voltage unbalance, over/under voltage, voltage and current harmonics and current unbalance.
  • Power Analysis: This is defined as viewing power quality as well as surges, swells, transients, interruption, etc. and requires datalogging capabilities.
  • Electrical Signature Analysis (ESA): A method of evaluating the motor system, which includes supply, control, motor, coupling, load and process, utilizing MCSA, VSA, TA, Inrush Analysis and Power Analysis.

The purpose of ESA is to obtain enough information, concerning the circuit being tested, to evaluate the health of the electrical system from supply through load.

ESA has been successfully applied in these applications:

  • AC induction motors
  • Variable Frequency Drives (VFD’s)
  • Wound Rotor Motors
  • Synchronous Machines
  • DC Motors
  • Alternators and Generators
  • Machine Tool Motors and Servos, including robotics
  • Driven equipment including Belted, Direct Drive and Geared
  • Transformers
  • Traction Equipment
  • And numerous other applications

What it comes down to is the ability to evaluate the information provided by ESA. That is the purpose of this lecture series.

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