ELECTRONIC PRINCIPLES - OD1647 - LESSON 1/TASK 1
f. Power Loss in an Inductor. Since an inductor (coil)
consists of a number of turns of wire, and since all wire has
some resistance, every inductor has a certain amount of
resistance. Normally this resistance is small. It is usually
neglected in solving various types of ac circuit problems
because the reactance of the inductor (the opposition to
alternating current, which will be discussed later) is so much
greater than the resistance that the resistance has a negligible
effect on the current.
(1) Copper Loss. However, since some inductors are designed
to carry relatively large amounts of current, considerable power
can be dissipated in the inductor even though the amount of
resistance in the inductor is small. This power is wasted power
and is called COPPER LOSS. The copper loss of an inductor can
be calculated by multiplying the square of the current in the
(2) Iron Losses. In addition to copper loss, an ironcore
coil (inductor) has two iron losses. These are called
HYSTERESIS LOSS and EDDYCURRENT LOSS. Hysteresis loss is due
to power that is consumed in reversing the magnetic field of the
inductor core each time the direction of current in the inductor
changes.
Eddycurrent loss is due to currents that are induced in the
iron core by the magnetic field around the turns of the coil.
These currents are called eddy currents and flow back and forth
in the iron core.
All these losses dissipate power in the form of heat. Since
this power cannot be returned to the electrical circuit, it is
lost power.
g. Mutual Inductance. Whenever two coils are located so that
the flux from one coil links with the turns of the other coil, a
change of flux in one coil causes an emf to be induced in the
other coil. This allows the energy from one coil to be
transferred or coupled to the other coil. The two coils are
said to be coupled or linked by the property of MUTUAL
INDUCTANCE. The amount of mutual inductance depends on the
relative positions of the two coils. This is shown in figure 22
on the following page. If the coils are separated a
considerable distance, the amount of
35
Previous Page
