The insulation resistance measurement is used to measure the insulation strength of electric coils and commutators. DC current is used to measure the resistance against ground potential. The discharge capacity of the insulation system is investigated in this process.
The voltage drop at the insulation is measured and the resistance is calculated from this measurement. In order to achieve comparable values, the measurement lasts exactly 60 seconds in accordance with the VDE standard and is extended to 600 seconds for the polarization index measurement.
During polarization index measurement the "polarization index" is calculated from the ratio of the two measurements (10 min/1 min).

Industry-standard measurements for measuring insulation resistance

Fields of application

Regulations that apply in the industrial sector require an insulation resistance of 1000 Ohm per volt of voltage at 75°C coil temperature. This must be implemented on motors, generators, and transformers.
A low insulation value and/or a polarization index below 2 can be considered an indicator for contamination or moisture. Therefore the machine should be cleaned and dried as an initial step, if there are poor insulation values and low polarization index values.
These two measurements are a primary action for the preventive maintenance of your machines and systems.

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Our goal is your benefit: Our experience in the area of machine diagnostics will support you in the evaluation of your machine's condition

Your benefit

  • It is possible to evaluate the condition of the insulation
  • Recommended actions can be derived from these measurements
  • The condition assessment makes it possible to plan downtimes for overhauls