Insulation reliability of windings for large rotating machines

The insulation reliability of a winding has a direct relationship to the reliability of its individual coils. As previously described, this depends upon tests made on components and on assembled coils in various phases of manufacture. Past experience is the major contributor in specifying limits for these tests. Machines in service have proven reliability, by long, continuous periods of trouble-free operation. A continued record of reliable insulation is assured by requiring at least the same test results on components and assembled coils as in the past. For these comparisons, statistical quality control principles are employed.