Ignition System; Construction; Description Of Operation - Stihl 009 User Manual

STIHL 009, 010, 011
4.

IGNITION SYSTEM

4.1

Construction

The 010 is equipped with a breaker-
controlled magneto ignition system
which requires neither a battery nor
a generator.
The Phelon ignition system is of com-
ponent-type construction (ignition ar-
mature and control unit are arranged
separately) and consists of three main
parts - the flywheel (magnet wheel),
ignition armature and the control unit.
The flywheel carries the permanent
magnet with a north and south pole
and is located on the crankshaft stub.
The ignition armature is mounted in
the crankcase on the periphery of the
flywheel and can be adjusted within
certain close limits by means of slots
in the iron core.
The ignition's control unit, i. e. the con-
tact set with condenser, is screwed to
the crankcase behind the flywheel.
4.2

Description of Operation

Every magneto ignition system ope-
rates on the principle of magnetic
induction. On the breaker-controlled
ignition system (and transistorized
ignitions) this involves only "dynamic
induction".
In dynamic induction the electric
current is generated in a conductor
by moving the conductor through the
flux lines of a magnetic field. The
magnitude of the induced voltage is
basically dependent on the strength
of the magnetic field and the speed of
the flux change. This in turn is in-
fluenced mainly by the intensity of the
movement.
In terms of the magneto ignition
system this means: As the flywheel
rotates the flux lines flowing between
the poles of the permanent magnet,
from north pole to south pole, create
a magnetic flux in the iron core of the
coils. The flux lines of this magnetic
field cut through the wire windings of
the respective coil and induce a low
tension current. The magnitude of the
voltage is, therefore, basically depen
dent on the rotational speed of the
flywheel.
In the case of static induction on the
other hand, the voltage is created in a
conductor by a magnetic field chang
ing its strength or flow direction, the
conductor being situated in the mag
netic field which is produced by an
electric current (transformer prin
ciple). The magnitude of the induced
voltage is principally depended on the
strength of the primary current which
generates the magnetic field and the
ratio of turns between the primary and
secondary coils (transformation ratio).
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