Originally Posted by Alejandro Mercado
Damocles i still dont indestand , your question, and for what is the inverter?
Short answer: The INVERTER
converts DC into AC, permitting transforming 12 VDC into maybe, say, 400-600 V AC(or more). The higher-voltage AC is rectified, charges a capacitor, then . . . the capacitor is discharged through the ignition coil's primary windings, the consequent pulse transformed to an even higher voltage through the ignition coil's secondary windings, causing a spark.
Long answer (courtesy WikipediA):
The AC-CDI module obtains its electricity source solely from the alternating current produced by the alternator. [As in Generation 1 KLR650s] The AC-CDI system is the most basic CDI system which is widely used in small engines.
Note that not all small engine ignition systems are CDI. Some engines like older Briggs and Stratton use magneto ignition.
[There we have it; "magneto ignition," an arrangement I tried (unsuccessfully) to reference in a previous discussion with another poster.] The entire ignition system, coil and points, are under the magnetized flywheel. [Note: Just incidentally, a "magneto ignition" uses coil and points.]
Another sort of ignition system commonly used on small off-road motorcycles in the 1960s and 1970s was called Energy Transfer. A coil under the flywheel generated a strong DC current pulse as the flywheel magnet moved over it. This DC current flowed through a wire to an ignition coil mounted outside of the engine. The points sometimes were under the flywheel for two-stroke engines, and commonly on the camshaft for four-stroke engines. This system worked like all Kettering (points/coil) ignition systems... the opening points trigger the collapse of the magnetic field in the ignition coil, producing a high voltage pulse which flows through the spark plug wire to the spark plug.
If the engine was rotated while examining the wave-form output of the coil with an oscilloscope, it would appear to be AC. Since the charge-time of the coil corresponds to much less than a full revolution of the crank, the coil really 'sees' only DC current for charging the external ignition coil.
Some electronic ignition systems exist that are not CDI.
[As in, Generation 2 KLR650s.] These systems use a transistor to switch the charging current to the coil off and on at the appropriate times. This eliminated the problem of burned and worn points, and provided a hotter spark because of the faster voltage rise and collapse time in the ignition coil.
The DC-CDI module is powered by the battery, and therefore an additional DC/AC inverter circuit is included in the CDI module to raise the 12 V DC to 400-600 V DC, making the CDI module slightly larger.
[NOT the case for Generation 2 KLR650s; the model has no stinkin' CDI whatsoever.] However, vehicles that use DC-CDI systems have more precise ignition timing and the engine can be started more easily when cold.
Summary (in the general context of engines, as on motorcycles):
AC-CDIs are powered by alternating current from the engine's fundamental electric power system. [Think alternator, stator.]
DC-CDIs are powered by low-voltage DC [As in, rectified, regulated 12 VDC], but must have an inverter in the circuit to convert the DC to AC for high voltage step-up; consequent higher-voltage rectified and used to charge a capacitor.
MAGNETO IGNITIONS [As the phrase is commonly used in Ignitioniana] have no CDI whatsoever, rather, consist of inductive discharge systems with contact points.
Now, WikipediA, and I, HAVE SPOKEN!