Mazda Xedos 6. Handbuch - teil 198
Electrical control
A current through the primary coil induces a
magnetic field. The moment the current is
switched of, the magnetic field suddenly
disappears. This change of magnetic field
induces an induction voltage and causes a
spark.
The amperage before switching the current off
should be high enough to create a high change
of magnetic field the moment the current is
switched off.
Therefore the current through the primary coil
is controlled electronically.
The ignition module is supplied with a current
limited circuit. Using this in combination with a
low resistance ignition coil the amperage does
not depend on the battery voltage.
During the time the current is switched off, the
voltage over the ignition module is 12 Volts.
The moment the current is switched on, the
voltage drops to 0 Volts. From this moment on
the current increases until the limiting value is
reached.
The oscilloscope images A and B gives you an
example of the primary voltage measured on
two different current limiting circuits.
By increasing the voltage over the ignition
module, the voltage over the primary coil
decreases. This causes a limited current in
oscilloscope image A.
The ignition module in oscilloscope image B
switches the current on and off to limit the
current.