EDA-III motor insulation resistance test

EDA-III motor insulation resistance test

Insulation Evaluation System for Motors and Generators

The EDA system is ideal for the evaluation and diagnosis of the insulation condition in electrical rotary machines such as motors, generators, alternators, etc.


Its main function is to analyse the condition of the stator winding insulation, using DC voltage levels without risk to the element under test.
The system obtains various parameters to evaluate the state of each of the components that make up the insulation in a rotary machine. Using these values and changes over time, it is possible to make a reliable diagnosis of the overall condition or specific problems, such as dirtiness, internal or external humidity, insulation degradation, partial discharges, etc.
The system has been developed using the experiences of users, resulting in a completely automated system with optimized measuring features.


Results of the tests made by the system are presented 2 ways, Numerically and Graphically. The numeric information is presented by means of parameters list, automatically calculated with the corresponding corrections. The graphic information is presented with the charge and discharge current curves for each test voltage and a polarization index curve. The polarization curve may be optionally smoothed to remove unwanted transient external effects from the real measurement.

Numeric Information:

  • Actual test voltage.
  • External temperature.
  • External humidity.
  • DC and 1 kHz Capacitance.
  • Ratio of DC and 1 kHz capacitances.
  • Test Voltage Ratio.

For each test voltage, the EDA system carries out a charge and discharge cycle from which we get the following information:

  • Insulation resistance (corrected to 20º and 40ºC).
  • Polarization index.
  • Absorption index.
  • Leakage current.
  • Standardised leakage intensity (voltage and capacitance).
  • Leakage current ratio at each test voltage.
  • Absorption ratio.
  • Leakage/Re-absorption current ratio.
  • Re-absorption current.
  • Re-absorption current standardised for insulation thickness.
  • Time constant

The data information is associated with the test voltage, indicating the results for each test. Information is provided with each parameter to determine the state of the parts which makes up the insulation of the electrical rotary machine.

Graphic Information:

Also provided is a graphic display of the charge and discharge currents for each test voltage. Additionally a “standard” curve is displayed to easily determine departures from the linear insulation behaviour versus the voltage increase. A curve is displayed during the polarisation index test.
Curves may be optionally smoothed to remove unwanted transient external effects from the real measurements.


  • For initial reception and quality control of rotary machines (generators, alternators, LV and MV motors). Forming a part of a maintenance program on rotary machines, where a non-programmed failure would represent a high costs, risks and installation outage, and of course, to verify failures.
  • To create a historial of the motors, etc. tested as the EDA system generates a report. In this report all technical data of previous tests are presented in a structured manner to easy follow the history of the element tested.
  • To evaluate the parameters tested, anticipating failures and to diagnose the type of problem, thus planning in advance, the necessary maintenance steps required.
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