Method of Obtaining Constant Electrical Output power in Train
- The most important requirement of train lighting is to obtain constant output irrespective of locomotive speed.
- To achieve this there are three methods of obtaining constant output. They are as follows :
- Belt Driven Generator
- Three Brush Generator
- Rosenberg Generator
- To make the output of the generator self regulating, the conventional generator is modified.
- In this, instead of two brushes three brushes are used.
- The brushes A, B and C are placed at right angles to each other as shown in the Figure
- The brushes A and C are used to excite the field winding and the output across brushes A and B is given to the load.
- As the speed of the train increases, the EMF across the brushes A and B also increases. This will further increase in the load current.
- This increase in load current will cause increase in the armature reaction a.
- This makes more and more distortion in the main flux. This further reduces the induced EMF across brushes AC, which helps in reducing the field excitation.
- This will cause the reduction in the EMF generated across main brushes AB.