Developments in A. C. winding practice

During the last few years there has been a tendency, both in the Transvaal and in the Orange Free State, to install a greater proportion of three-phase a.c. winders as compared to the Ward-Leonard types and some of the reasons for this change are given; these include improvements in dynamic braking and the use of twin a.c. motors of large b.h.p. outputs. This paper reviews the theory of uncompensated and compensated d.c. dyanmic braking, the question of load sharing of twin motors and describes some changes and refinements in rotor control gear specifications which concern primarily a.c. winders.