Generac Power Systems 940 Portable Generator User Manual


 
Section 1.1
GENERATOR FUNDAMENTALS
CAPACITIVE REACTANCE:
This condition occurs when current leads voltage
(Figure 9). It might be thought of as the ability to oppose
change in voltage. Capacitance exists in a circuit when
certain devices are ~a) capable of storing electrical
charges as voltage increases and (b) discharging these
stored charges when the voltage decreases.
Figure 9. Capacitive Reactance
WHAT IS AN "IMPACT PLUS" UNIT?:
The Impact Plus is a computer controlled generator
that uses an inverter to create a superior sine wave
and maintain a steady frequency. These units are dif-
ferent from conventional generators in that the perfor-
mance of the engine and AC generator are more
accurately matched over a wide range of power
needs. The Impact Plus computer controlled genera-
tor provides greater efficiency of both the engine and
the generator while maintaining electrical output with-
in an acceptable voltage range. The frequency is con-
trolled by the inverter and is maintained at a steady
60 Hz signal throughout the load range.
Computer controlled generator units have the ability
to operate the engine over a wide range of speeds,
while conventional generators will deliver correct AC
frequency and voltage only at a fixed rpm.
Unlike conventional AC generators, the Impact Plus
unit can match engine speed to load requirements.
This provides several advantages, as follows:
Smaller engines can be used to produce more
power than on a conventional generator, since it
can be allowed to run at a higher speed.
When the load is reduced, the engine can run at
slower than the usual speeds. This improves fuel
economy and reduces engine noise.
The Impact Plus unit can be operated closer to its
peak power point at all times, because output volt-
age and current are functions of engine speed. This
allows for a much more compact generator design.
IMPACT PLUS SYSTEM OVERVIEW:
Figure 10 is a block diagram of the Impact Plus sys-
tem. The major elements of the system are represent-
ed in the diagram. Operation of the system may be
described briefly as follows:
1. The engine is directly coupled to a permanent magnet type
Rotor, so the Rotor runs at the same speed as the engine.
2. As the Rotor turns, its magnetic field cuts across the Stator
windings to induce a voltage into the Stator.
Page 1.1-4
Figure 10. Block Diagram of the Impact 36 Plus System