The basis of a single-loop d.c. generator is shown in figure 6.1. A magnetic field is established by the field winding on the salient pole system which is fixed to the frame of the machine. The armature winding is driven round by a prime mover (that is, turbine, diesel engine, water wheel, etc.). At the instant of time illustrated in the figure, the direction of the induced e.m.f. in the conductor WX is from W to X, and in YZ is from Y to Z (hint: use Fleming’s right-hand rule). Since the two e.m.f.s are additive, current flows out of terminal A of the generator. When the armature winding has rotated through 180° in the direction of rotation, conductor YZ passes under the N-pole and the direction of the induced e.m.f. in YZ has reversed. The armature conductors are connected to the external circuit via a commutator and carbon brushes. The function of the commutator is twofold; firstly it provides an electrical connection between the rotating armature and the external circuit, and secondly it permits reversal of current in the armature winding while maintaining a d.c. potential between the terminals of the machine.
Weitere Kapitel dieses Buchs durch Wischen aufrufen
- D. C. Machines
Noel M. Morris
- Macmillan Education UK