Recorded values · documented factors · no energization verdict
Documented Insulation-Resistance Normalizer and PI Calculator
Normalize a one-minute winding insulation-resistance reading with the exact multiplication factor from your controlled procedure, calculate the polarization index when a ten-minute reading exists, and compare only with the documented minimum you enter.
Documented arithmetic result
Implemented arithmetic
PI = R₁₀ / R₁ (only when a valid R₁₀ is entered)
numeric margin = Rref / Rmin
K is not generated here. Enter the factor whose documented convention explicitly multiplies the measured R₁ to obtain resistance at the entered reference temperature. The former page applied 0.5((40−T)/10) universally, although temperature behaviour depends on the insulation system and the correction convention must be confirmed. The calculator performs an inequality against the supplied Rmin; it does not turn that one comparison into a condition grade, failure diagnosis or energization decision.
IEEE 43 status and scope boundary
The official IEEE page lists IEEE 43-2013, “IEEE Recommended Practice for Testing Insulation Resistance of Electric Machinery,” as Inactive-Reserved since 21 March 2024. IEEE explains that an inactive-reserved standard is no longer being reviewed or assessed for accuracy or relevance. An active P43 revision project, approved 6 December 2023, is intended to supersede IEEE 43-2013 but is not a published replacement standard on the official page as of 12 July 2026. Exact current clauses, winding-specific minimums, test-voltage tables and exceptions therefore remain NEEDS_LICENSED_SOURCE; this page does not reproduce them or call its arithmetic an IEEE formula.
PI and temperature correction
The current Megger BM5200 documentation ja Fluke insulation-testing guide support the arithmetic definition PI=R₁₀/R₁. They also emphasize comparable temperatures/correction and trending. They do not justify the former universal labels “dangerous,” “questionable,” “good” and “excellent” for every winding. PI applicability can be limited by insulation system, very high one-minute resistance, instrument range/current limit, leakage paths and the controlled procedure.
Why no automatic test voltage or pass/fail verdict?
The appropriate test voltage and acceptance criteria depend on machine/winding construction, rating, condition, manufacturer instructions and the applicable controlled procedure. Fluke’s motor test safety guidance warns that insulation-test voltage can damage connected electronic controls and describes lockout/tagout, isolation and post-test discharge. A single resistance or PI result cannot identify moisture or contamination by itself and cannot authorize energization.
Required record and review
Retain the raw time-resistance readings, actual test voltage and duration, winding temperature, humidity/environment where required, machine and winding connection, instrument/range/guard use, correction source and convention, previous comparable results, discharge confirmation and deviations from procedure. Resolve a value below the entered criterion under the controlling procedure; do not infer that a value above it proves all insulation or machine conditions acceptable.
