Abstract
To ensure that the materials used in the construction of a rotating electrical machine are utilized economically it is necessary to be able to predict the temperature distribution within the machine.
A resistance network analogue representation of the stator core and windings is derived, based on the finite difference approximation to the heat flow equations. A solution of the analogue is achieved by matrix methods on a digital computer. The advantages of this particular analogue representation are that the effects of axial heat flow in the copper and changes in the air temperature in the radial air ducts are taken into account. The validity and accuracy of the analogue representation are checked by comparing the results with those obtained from detailed temperature measurements on a production machine. It is shown that the present standard methods of measuring winding temperature are inadequate for determining the actual copper temperature.
Under certain circumstances high temperatures can be obtained in the endwinding region of a machine. These temperatures are undetected by the standard method of temperature measurement and are shown to be due to the low value of endwinding insulation thermal conductivity.
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