Explain why in the design of the iron cored electrical machines magnetic circuit analysis the magnetic characteristics in the first quadrant is considered, while in that of Permanent Magnet Machines the magnetic characteristics in the second quadrant is considered?
b- Explain why in the design of the iron cored electrical machines magnetic circuit analysis the magnetic characteristics in the first quadrant is considered, while in that of Permanent Magnet Machines the magnetic characteristics in the second quadrant is considered?
While designing a iron cored electrical machine the magnetic circuit analysis generally involves the first quadrant of magnetic characteristics or first quadrant of the hysteresis loop.
Because for an iron cored machine the material must be such that it does not retain magnetism even after H=0.
Iron cored machines are made of SOFT MAGNETIC MATERIALS which have the following properties.
- They have low value of residual magnetism.
- They have low coercive force.
- They generally have high permeability.
- They have a NARROW HYSTERESIS LOOP.
These soft magnetic materials expend less energy for traversal of one hysteresis loop when an external magnetic field is applied. That is these materials can be easily magnetized and demagnetized in quick succession. this property finds perfect use in IRON CORED ELECTRICAL MACHINES.
The first quadrant of the hysteresis loop or magnetic characteristics represents the ability of a magnetic material to get magnetized easily. the cores of machines need to be magnetized and demagnetized easily.
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