Page 490 - Basic Electrical Engineering

Where k is the eddy current coefficient which depends upon the type of
e
the magnetic material.

To reduce eddy current loss in a magnetic material, the thickness is
reduced. Laminated sheets are used to build a core instead of using one piece

solid core. The sum of hysteresis loss and eddy current loss is called core loss
or iron loss.

5.5 MAGNETIC CIRCUITS

All electrical machines and equipment are made of magnetic material as their
core. A winding which carries current is placed around the core. The core and

the current-carrying coil around the core forms an electro magnet. Thus, we
can say that an electro magnet is made using a piece of magnetic material as

the core and around which a current-carrying coil is placed. Let us consider a
bar-type piece of magnetic material, i.e., a piece of iron being made in to an
electro magnet. A coil has been wound around it. Current is being allowed to

flow through the coil from a source of supply, say a battery, as shown in Fig.
5.13 (b). The magnetizing force applied is the product of the number of turns

of the coil (N) and the current flowing through the coil (I). Let us examine
how the magnetizing force, NI magnetizes the magnetic material.

Figure 5.13 (a) Orientation of magnetic dipoles before the application of magnetizing force; (b) on
application of the magnetizing force, NI, the magnetic dipoles get oriented in one direction