01․ A DC generator can be considered as
A DC generator can be considered as a rotating amplifier or amplidyne as it amplifies the signal power through armature current.
02․ In DC generators, the cause of rapid brush wear may be
In DC generators, the causes of rapid brush wear are the following:
- severe sparking
- imperfect contact
- rough commutator surface
- excessive spring pressure
- abrasion from dust
03․ The commutator segments are connected to the armature conductors by means of
The commutator segments are connected to the armature conductors by means of copper lugs. A copper lug is shown below.
04․ In a DC generator the ripples in the direct emf generated are reduced by
In a DC generator the ripples in the direct emf generated are reduced by using commutator with large number of segments. This is because commutator with large number of segments will rectify the AC emf generated in the armature to direct emf in a better way.
05․ Which of following components of a DC generator plays vital role for providing direct electric current of a DC generator?
Commutator and brush assembly plays a vital role for providing direct electric current of a DC generator.
06․ The voltage drop for which of the following types of brush can be expected to be least?
The voltage drop for metal graphite brush is least around 0.5V-1V whereas the voltage drop for carbon or graphite brushes is around 1.5V-2.5V.
07․ Satisfactory commutation of DC machine requires
Satisfactory commutation of DC machine requires the following:
- Smooth and concentric commutator that is properly undercut
- Smooth motion of brushes within the holder
- Proper grade and size of the brush
- Good insulation between commutator segments.
08․ To achieve spark less commutation brushes of DC generator are rocked ahead so as to bring them
Due to armature reaction, the MNA is shifted in the direction of rotation in a generator and against the direction of rotation in a motor. As a result, rotational emfs are induced in the coils undergoing commutation which leads to sparking. To achieve spark less commutation brushes of DC generator are rocked ahead so as to bring them just ahead of magnetic neutral axis.
09․ In a DC generator in order to reduce sparking at brushes, the self-induced emf in the coil is neutralized by all of the following except
In a DC generator in order to reduce sparking at brushes, the self-induced emf in the coil is not neutralized by inter poles. The inter poles only reduce the harmful effects of armature reaction.
10․ The rapid wear of brushes takes place due to
In DC generators, the causes of rapid brush wear are the following:
- severe sparking
- imperfect contact
- rough commutator surface
- excessive spring pressure
- abrasion from dust
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