Electrical Engineering XYZ MCQs
In DC machines, the shape of armature MMF wave is:
- Triangular and directed towards main pole
- Saddle shape
- Peaky in nature
- Triangular and directed towards brush axis
Correct answer: 4. Triangular and directed towards brush axis
Explanation:
In DC machines, the shape of the armature MMF (magnetomotive force) wave is triangular and directed towards the brush axis. This triangular shape is a result of the winding arrangement on the armature. The armature MMF wave represents the distribution of magnetic flux produced by the armature current.
The winding on the armature of a DC machine is usually arranged in the form of coils, and when the armature current flows through these coils, it creates a magnetic field. The resulting MMF wave is triangular because the winding arrangement causes the magnetic field to vary sinusoidally along the circumference of the armature.
The direction of the triangular MMF wave is towards the brush axis, which is the axis along which the brushes make electrical contact with the rotating armature. This direction is chosen for better commutation, ensuring a smooth and continuous flow of current in the DC machine.
Therefore, the correct choice is “Triangular and directed towards brush axis.