138 Electrical Power Systems Technology
Slip Ring/Brush Assembly
AC Sine Wave
Single-Phase AC Generator
Rotating-Armature Method
Rotating-Field Method
Three-Phase AC Generator
Three-Phase Wye Connection
Three-Phase Delta Connection
High-Speed Generator
Low-Speed Generator
Frequency
Harmonics
Voltage Regulation
Efficiency
ELECTROMAGNETIC INDUCTION
The basic principle that allows electrical power to be produced by
alternators was discovered in the early 1800s by Michael Faraday, an
English scientist. Faraday’s Law is the basis of electrical power produc-
tion. The principle of electromagnetic induction was one of the most im-
portant discoveries in the development of modern technology. Without
electrical power, our lives would certainly be different. Electromagnetic
induction, as the name implies, involves electricity and magnetism.
When electrical conductors, such as alternator windings, are moved
within a magnetic field, an electrical current develops in the conductors.
The electrical current produced in this way is caned an induced current. A
simplified illustration showing how induced electrical current develops
is shown in Figure 6-1
A conductor is placed within the magnetic field of a horseshoe mag-
net so that the left side of the magnet has a north polarity (N), and the
right side has a south polarity (S). Magnetic lines of force travel from the
north polarity of the magnet to the south polarity. The ends of the conduc-
tor are connected to a current meter to measure the induced current. The
meter is the zero-centered type, so its needle can move either to the left or
to the right. When the conductor is moved, current will flow through the
conductor. Electromagnetic induction takes place whenever there is relative
motion between the conductor and the magnetic field. Either the conduc-