Generac Power Systems 940-2, 941-2 Electrical Units, Alternating Current Sine Wave

Section 1.1

GENERATOR FUNDAMENTALS

Figure 4. Operation of a Simple Generator

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-

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.

Page 1.1-2