Generac Power Systems 941-2 Service Manual page 8

Section 1.1
GENERATOR FUNDAMENTALS
ALTERNATING CURRENT
A simple generator consists of a coil of wires called a
Stator and a magnetic field called a Rotor. As the
Rotor's magnetic field cuts across the Stator coil, a
voltage is induced into the Stator windings. The
amount of induced voltage is equal to the strength of
the magnetic field.
See Figure 4. The current alternates according to the
position of the Rotor's poles in relation to the position
of the Stator. At 0° and again at 180°, no current flow
is produced. At 90° of Rotor rotation, current flow
reaches a maximum positive value. Rotor rotation to
270° brings another maximum flow of current.
However, at 270° the current flow has reversed in
polarity and now flows in the opposite direction.
ELECTRICAL UNITS
AMPERE:
The rate of electron flow in a circuit is represented by
the AMPERE. The ampere is the number of electrons
flowing past a given point at a given time. One
AMPERE is equal to just slightly more than six thou-
sand million billion electrons per second.
With alternating current (AC), the electrons flow first
in one direction, then reverse and move in the oppo-
site direction. They will repeat this cycle at regular
intervals. A wave diagram, called a "sine wave"
shows that current goes from zero to maximum posi-
tive value, then reverses and goes from zero to maxi-
Page 1.1-2
Figure 4. Operation of a Simple Generator
mum negative value. Two reversals of current flow is
called a cycle. The number of cycles per second is
called frequency and is usually stated in "Hertz".
Figure 5. Alternating Current Sine Wave
VOLT:
The VOLT is the unit used to measure electrical
PRESSURE, or the difference in electrical potential
that causes electrons :o flow. Very few electrons will
flow when voltage is weak. More electrons will flow as
voltage becomes stronger. VOLTAGE may be consid-
ered to be a state of unbalance and current flow as
an attempt to regain balance. One volt is the amount
of EMF that will cause a current of 1 ampere to flow
through 1 ohm of resistance.