Electrical Engineering XYZ MCQs
The interpoles in DC machines have a tapering shape in order to:
- Economize on the material required for interpoles and their windings
- Increase the acceleration of commutation
- Reduce the overall weight
- Reduce the saturation in the interpole
Correct answer: 4. Reduce the saturation in the interpole
Explanation: Interpoles are additional poles placed between the main poles of a DC machine to improve commutation, which is the process of smoothly transferring current from one armature coil to another as the armature rotates. The tapering shape of interpoles is designed to reduce saturation in the interpole region.
Saturation occurs when the magnetic field strength reaches a point where the magnetic material (in this case, the interpole winding) can no longer be magnetized further. Tapering the shape of interpoles helps in reducing saturation by distributing the magnetic flux more evenly along the interpole length.
Reducing saturation is important because it helps in maintaining a more uniform magnetic field in the interpole region. This, in turn, improves commutation and reduces the likelihood of sparking and arcing at the brushes, resulting in smoother and more efficient operation of the DC machine.
The other options are not the primary reasons for the tapering shape of interpoles:
- Economize on the material required for interpoles and their windings: While tapering may have some effect on material usage, the primary goal is to improve performance rather than to save on materials.
- Increase the acceleration of commutation: Tapering alone does not directly increase the acceleration of commutation. The main purpose is to reduce saturation and improve the magnetic field distribution.
- Reduce the overall weight: Tapering may have some impact on weight, but the primary purpose is not weight reduction. The main goal is to optimize magnetic field characteristics for better commutation.