Tom Bishop, P.E.
EASA Senior Technical Support Specialist
Note: This "encore" technical article first appeared in the September 2004 issue of Currents.
ll of us in the electrical apparatus service industry test the winding ground insulation resistance of machines such as motors and generators. A frequent question is: What is the minimum acceptable megohm (M.) value for this winding? The good news is that there is a standard that identifies minimum values for insulation resistance of rotating machines.
That standard is the “IEEE Recommended Practice for Testing Insulation Resistance of Rotating Machinery,” IEEE Std 43-2000. The EASA “Recommended Practice For The Repair Of Rotating Electrical Apparatus,” ANSI/EASA AR 100-2010, uses IEEE 43 for its insulation resistance test references. Note that IEEE 43 only applies to rotating machinery. There is no equivalent standard for non-rotating electrical machinery such as transformers. In this article we will delve into determining minimum insulation resistance for rotating electrical machinery.
LOGIN TO VIEW AND DOWNLOAD THE ARTICLE