Large a.c. motors

Abstract

This review covers the range of basic large a.c.motors,comprising squirrel-cage and slip-ring induction,synchronous and a.c.-commutator motors,in the output range of 1-20/30 MW,and the size range of 0-5-30 kW per rev/min,with centre heights ranging from 450 to 1250 mm. The underlying theme may be described in general terms as 'system design 1 in the widest sense; i.e. the effect of the environment on motor design and application, and vice versa. Thus, amongst the major topics covered are stator-insulation requirements and techniques, with particular reference to the surge voltages encountered in modern supply systems that have high short-circuit capacities. This leads to the consideration of system-stability problems on the one hand, and the choice of enclosures on the other. Conversely,the effect of motors on the environment, e.g. noise and the problems of heat removal (again affecting the choice of enclosures) are dealt with as complementary problems. With respect to motor design proper, emphasis is placed on aerodynamic and thermodynamic problems, and the importance of 2nd-order electromagnetic phenomena and reliability. To allow the reader to obtain detailed information (which cannot be covered in a broad survey of this type) on specific subjects, a carefully selected list of relevant references is given.