Figure 15-22. Typical Magneto System.
A means of developing electricity.
an extremely hot spark can be produced across the
spark plug gap.
(2) A transforming device to Increase the
d. The magneto ignition system generally is
voltage of the electricity developed.
reliable, requires little maintenance, and does not have a
(3) An Interrupting device to determine the
battery to run down or wear out.
proper timing of the electrical impulses.
disadvantage is that it turns so slowly during the cranking
of the engine that a hot spark Is not produced.
(4) A distributor to direct the electrical impulses
Therefore, a supplementary high-voltage source must be
In the proper order to the different cylinders.
provided. This may be a booster magneto or a high-
tension coil to which primary current is supplied by a
A spark gap In each cylinder In the engine.
battery. In some magnetos, an Impulse starter is
provided that produces high armature speeds at engine
(6) The proper wiring and switches to bring
cranking speeds to provide a hot spark.
these units together to form the Ignition system.
15-10. Source of Electrical Energy (Fig. 15-23).
c. The first four units are contained within the
magneto. The spark plug supplies the fifth unit, wiring
In studying the magneto, It should be understood that
and switches make up the sixth unit. The same four
three things are necessary to Induce voltage: an
fundamental units that make up the magneto also can be
electrical conductor, a magnetic field, and relative
classified broadly as just two parts: a generator and a
motion between the field and the conductor. In the
The generator provides a means of
magneto, a permanent magnet supplies the magnetic
Inducing low voltage In a primary circuit.
field, a wire coil is the conductor, and the engine
transformer changes the low voltage of the primary
circuit to the high voltage In a secondary circuit so that