IEEE 43

Description / Abstract: This document describes a recommended procedure for measuring insulation resistance of armature and field windings in rotating machines rated 750 W or greater. It applies to synchronous machines, induction machines, dc machines, and synchronous condensers. It does not apply to fractional-horsepower machines.

The document also describes typical insulation resistance characteristics of rotating machine windings and how these characteristics indicate winding condition. It recommends minimum acceptable values of insulation resistance for ac and dc rotating machine windings.

Other IEEE standards that include information on insulation resistance measurement are listed in Clause 2.

Purpose

The purpose of this recommended practice is to address the following:

a) Define insulation resistance and polarization index testing of the winding of a rotating machine.

b) Review the factors that affect or change insulation resistance characteristics.

c) Recommend uniform test conditions.

d) Recommend information methods for measuring insulation resistance with precautions to avoid erroneous results.

e) Provide a basis for interpreting insulation resistance test results to estimate winding suitability for service or for an overvoltage test. In particular, this standard describes typical insulation problems detected by the insulation resistance test.

f) Present recommended minimum acceptable insulation resistance values and polarization indices for various types of rotating machines.