Recent developments in turbo-generators

The subject of ventilation is first dealt with, the different systems used in the past, and recent developments, being reviewed. Radial, axial, radial-axial and multiple-inlet systems are referred to, and internal and external fans are discussed. The elimination of eddy currents is next considered, the various methods, past and present, being reviewed. These include: Twisted and transposed windings; twisted and transposed slot conductors; twisting and transposition of end-connections; combination of transposed slot conductors and end-connections. The paper then deals with the magnetic field of stator endconnections and discusses the following matters: Local heating produced in end of core, stator end-plate and stator endconnections; measurements by exploring coils under different load conditions, i.e. leading load, lagging load and shortcircuit; effect of squirrel cage located between stator winding and rotor coil-retaining rings of single-phase generator; neutralization of end field by copper screening plate. In the next section the subject of insulation is treated, the following being considered: Vibration of conductors; swelling of insulation; smooth core design; expansion and contraction of armature conductors; crinkling of insulation; bakelized conductors; clamping of stator winding. Rotor forgings are discussed, especially in connection with the relative advantages of oil-quenching and annealing. Finally, the subject of coil-retaining rings is dealt with, and the method of support, difficulties due to rigidly supported rings, and non-magnetic rings are discussed.