Generac Power Systems 941-2 - Manual (Page 99)

Section 6.4
ENGINE IGNITION SYSTEM
INTRODUCTION
The engine ignition system consists of the following
major components:
• Ignition Cage Assembly.
• Ignition Sensor Assembly.
• Ignition Module (IM).
• Ignition Coil (IC).
• Spark Plug (SP1).
IGNITION CAGE ASSEMBLY
An IGNITION CAGE ASSEMBLY is factory installed
onto the permanent magnet rotor hub. Two magnets
are installed in the cage as shown in Figure 1 (50°
apart), so that the north pole of one magnet faces
away from the cage outer periphery and the north
pole of the other magnet faces toward the cage outer
periphery. A special fixture is used to install the cage
onto the rotor hub so that the center line of the first
magnet is 68° away from the Rotor Hub mounting
hole as shown.
NOTE: Placement of the magnets on the Rotor
Hub at the exact position stated above results in
an ignition timing of 29 ° BTDC.
The Ignition Cage assembly cannot be replaced. The
entire Rotor Hub must be replaced. Replacement
Rotor Hubs will include a factory installed Ignition
Cage assembly, and Magnetic Housing Assembly.
NOTE: Also refer to "Permanent Magnet Rotor" in
Section 1.2 (Page 1.2-1).
Figure 1. Ignition Cage Assembly
IGNITION SENSOR
The Ignition Sensor is retained to the AC generator's
Stator Adapter by means of two M4-0.70 x 8mm
screws and lockwashers. The Sensor housing houses
a circuit board. The entire housing cavity is filled with
potting material.
As the generator's Permanent Magnet Rotor turns
during operation, magnets on the Ignition Cage rotate
past the Ignition Sensor to induce a timed low voltage
pulse into the Sensor. This voltage pulse is delivered
to an Ignition Module and serves as a timing pulse for
the Module.
Figure 2. Ignition Sensor
See Figure 3. The Sensor circuit board mounts solid
state components which are sensitive to magnetism.
Magnets in the Ignition Cage rotate past the Sensor,
causing the base of a transistor to be "pulsed". The
transistor acts much like a "switch" or a set of "con-
tact points". Pulsing the transistor base causes the
"switch" to close and connect the "OUT" lead to the
"GND" lead. This triggers the Ignition Module to deliv-
er a primary ignition current to the Ignition Coil at
timed intervals.
Figure 3. Ignition Sensor Schematic
IGNITION MODULE
While cranking and running, battery voltage is deliv-
ered to the Ignition Module via Wire 14 from the
A6060 circuit board. The Module will deliver this bat-
tery voltage to the Ignition Coil based on the "timing"
signal it receives from the Ignition Sensor.
The Ignition Module is retained in the generator con-
trol panel by two capscrews.
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