Revision Standard - Superseded. Superseded by 43-2000. Insulation resistance characteristics of rotating-machine windings and the manner in which these characteristics may serve to indicate the condition of the winding are described. The recommended procedure for the measurement of insulation resistance of windings of rotating machines rated 1 hp, 1 kW or greater is presented. The recommended minimum value of insulation resistance of alternating-current and direct-current rotating-machine windings is given. Synchronous machines, induction machines, direct-current machines, and synchronous converters are covered, as well as armature windings and field windings. Fractional-horsepower machines are not included.