IEEE 43-2013 insulation, winding resistance and balance

Motor Winding Test Report Format, Free PDF

One sheet per motor: nameplate, insulation resistance with PI, winding resistance with correction to 75 °C and imbalance, and an optional no-load run. Page 2 has the formulas, a correction table and guide values.

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  • No sign-up
  • A4, 2 pages
  • Formulas and limits included
Preview of the Motor Winding Test Report form
Download the PDF formA4, 2 pages

Print it at 100 % on A4. Page 1 is the form you fill in. The next page is the worksheet and reference.

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What is inside

  • Nameplate and job details, winding material, connection and thermal class
  • Timed insulation resistance for U, V, W and all windings to earth, with PI
  • Winding resistance for U-V, V-W and W-U, corrected to 75 °C, with change against the factory or previous value and an imbalance box
  • An optional no-load current and voltage table
  • Page 2: copper and aluminium correction formulas, a correction factor table from 10 to 85 °C, and findings with likely causes

How it was checked

The R75 / RT factors are calculated from the formula shown (constants 235 for copper, 225 for aluminium) and the worked example was checked by hand. The 2 % imbalance, minimum IR and PI values and the no-load current range are rules of thumb marked as guides. Use the factory report, the standard or your site limit.

Related

Common questions

How do I correct winding resistance to 75 °C?

For copper, multiply the reading by (235 + 75) divided by (235 + T), where T is the winding temperature in °C when you measured. For aluminium use 225 instead of 235. The form includes a ready table.

What winding resistance imbalance is acceptable?

Imbalance is (highest minus lowest) divided by the average, times 100. About 2 % is a commonly used guide, but the factory report and the previous test are a better reference than a single number.

Using the form

  • Limits and constants come from the standards named above, as commonly quoted. Check them against the edition you work to, and use the stricter of those and your specification.
  • Where a value is a common guide rather than a limit from a standard, the form says so.
  • This is a calculation aid for qualified people. It does not replace the standard, the instrument manual or your site safety procedure.

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CIE supplies insulation testers, earth testers, oil BDV testers, micro-ohm meters and relay test sets, with test certificate available on request.

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