Predetermination of the no-load magnetisation characteristics of large turbogenerators

A method is described for the determination of the no-load magnetisation characteristics of a turbogenerator from the dimensions of a design and from the magnetic properties of the stator and rotor iron. Because the calculation involves lengthy arithmetic, a digital computer is needed. As a test of the accuracy of the method, magnetisation curves have been computed for machines of capacity 120MW and 200 MW, and, when compared with curves obtained on the test bed, they show close agreement. A magnetisation curve is predicted for a 300 MW machine. For a typical design of large turbogenerator, the effect of changes in some of the rotor slots is considered with a view to optimising design from the point of view of the magnetic circuit. The modifications discussed are so chosen that the requirements relating to temperature rise and mechanical stress are not appreciably affected.