Abstract
The effective thermal conductivity of stacks of enamelled steel laminations (as used in the stator cores of large turbogenerators) is shown to depend on the fluid trapped between the laminations. The results of tests on stacks in a normal atmospheric environment have been adjusted for other environments, using a simple mathematical model. It is predicted that the effective thermal conductivity of a typical stack in an atmosphere of hydrogen is increased by a factor of about 2·8 compared with that in air. Tests on small samples of laminations in air, vacuum, and helium confirm that the hypothesis is reasonable. Hysteresis in the stress–strain curves of a typical stack indicates that the thermal behaviour of a stator core of a generator may change during its operational life.
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