Electrical Engineering XYZ MCQs
The armature of DC machine is made of silicon steel lamination to:
- Increase the permeability
- Reduce hysteresis loss only
- Reduce both eddy current and hysteresis loss
- Reduce eddy current loss only
Correct answer: 3. Reduce both eddy current and hysteresis loss
Explanation:
- Silicon Steel Lamination: In the construction of the armature (the rotating part) of a DC machine, silicon steel laminations are used. These laminations are made up of thin layers of silicon steel, which are insulated from each other. The use of silicon steel helps to reduce energy losses in the machine.
- Eddy Current Loss: When the armature rotates within the magnetic field of the machine, it experiences varying magnetic flux. This variation induces currents known as eddy currents in the armature. Eddy currents lead to energy losses in the form of heat due to the resistance of the armature material. By using silicon steel laminations, these losses are minimized because the thin insulated layers of silicon steel hinder the flow of these currents, reducing eddy current losses.
- Hysteresis Loss: Hysteresis loss occurs due to the continuous reversal of magnetization in the core material as the magnetic field changes direction. Silicon steel has high magnetic permeability, which means it can easily magnetize and demagnetize. This property reduces hysteresis losses significantly compared to other materials. Thus, using silicon steel laminations helps to minimize hysteresis losses as well.
Therefore, the use of silicon steel laminations in the armature of a DC machine serves to reduce both eddy current and hysteresis losses, making the machine more efficient.