| 摘要 |
PROBLEM TO BE SOLVED: To determine whether the stained state of the surface of a coil is allowable in practical use. SOLUTION: Tan δ-alternating voltage testing is carried out, in an environments of 25 deg.C-35 deg.C and relative humidities of 90-100% RH. When the differential coefficient of tan δ becomes negative in the rated voltage value of a dynamo-electric machine, it is determined that the state of surface stains in the surface of the coil is not allowable in practical use. |
