1975 年 24 巻 261 号 p. 526-533
In order to obtain the fundamental knowledge in clarifying thermal stress induced in the stator windings, the interaction mechanism between the conductor and insulation of the stator windings under axial load were examined theoretically and experimentally. The stress analysis was made with the aid of the equivalent model in which the stator windings was regarded as a composite structure consisting of the conductor and the insulation bonded by the adhesive. The experiments were carried out on six different kinds of model windings and the strain distributions induced on the insulation surface were measured by strain gauges under axial load. The electrical properties, such as tangent delta and breakdown voltage, were also measured under axial load and the variations in the electrical properties caused by the occurrence of mechanical damages were examined. The results obtained are as follows
(1) The interaction mechanism between the conductor and insulation of the stator windings followed the derivation shown in the stress analysis.
(2) When the axial load was applied, the tensile stress in the insulation was maximum at the center portion and the shearing stress in the adhesive was maximum at the end portion. Therefore, it was considered that the insulation windings should bear not only the tensile strength of insulation but also the shearing strength of the adhesive or of the insulation in the vicinity of the adhesive.
(3) The closed relationship existed between the occurrence of mechanical damages and the variations in the electrical properties. That is, the apparent variations were observed in the tangent delta characteristics when bonding failures took place in the adhesive and the remarkable reductions were observed in breakdown voltages when the insulation was broken.