Editing Ignition magneto (section)

== Design ==
A simple [[magneto]] (an electrical generator using permanent magnets) is able to produce relatively low [[voltage]] electricity, however it is unable to produce the high voltages required by a [[spark plug]] as used in most modern engines (aside from [[diesel engine]]s).<ref name="Cauldwell, 1941, 88" >{{Cite book |title=Aero Engines: for Pilots and Ground Engineers |last=Cauldwell  |first=O. |publisher=Pitman |year=1941 |page=88}}</ref> An ''ignition magneto'' also includes an electrical [[transformer]],<ref name="Cauldwell, 1941, 88" /> which converts the electricity to a higher voltage (with the trade-off being a corresponding reduction in the output [[electric current|current]]).<ref name="Cauldwell, 1941, 88" />

As the points begin to open, point spacing is initially such that the voltage across the primary coil would arc across the points. A [[capacitor]] is placed across the points which absorbs the energy stored in the [[leakage inductance]] of the primary coil, and slows the rise time of the primary winding voltage to allow the points to open fully.<ref name="continentalmotors">{{cite web |url=http://www.continentalmotors.aero/WorkArea/DownloadAsset.aspx?id=2147483664 |title=The Aircraft Magneto |publisher=Continental Ignition Systems |date=2011-08-31 |access-date=2016-06-21 |url-status=live |archive-url=https://web.archive.org/web/20150918025733/http://www.continentalmotors.aero/WorkArea/DownloadAsset.aspx?id=2147483664 |archive-date=2015-09-18 }}</ref>

A second coil, with many more turns than the primary, is wound on the same iron core to form an electrical [[transformer]]. The ratio of turns in the secondary winding to the number of turns in the primary winding, is called the ''turns ratio''. Voltage across the primary coil results in a proportional voltage being induced across the secondary winding of the coil. The turns ratio between the primary and secondary coil is selected so that the voltage across the secondary reaches a very high value, enough to arc across the gap of the spark plug. As the voltage of the primary winding rises to several hundred volts,<ref name="continentalmotors"/><ref>{{cite web|url=http://www.smokstak.com/articles/capacitors.html|title=Capacitors in Ignition Systems|website=www.smokstak.com|access-date=6 May 2018|url-status=live|archive-url=https://web.archive.org/web/20170709061159/https://www.smokstak.com/articles/capacitors.html|archive-date=9 July 2017}}</ref> the voltage on the secondary winding rises to several tens of thousands of volts, since the secondary winding typically has 100 times as many turns as the primary winding.<ref name="continentalmotors"/>

===Impulse coupling, induction vibrator, and booster coil===
{{Multiple image
|image1 = Induction Vibrator schematic.png
|footer = (Left) In a vibrator coil, points open and close rapidly, creating pulsating DC, or interrupted battery current. Electrical current flows from the battery through R1, vibrator points V1, and coil L2. The energized coil L2 opens vibrator points V1, interrupting the current flow through L2. The magnetic field about L2 collapses, and vibrator points V1 close again. Once more, current flows through L2, and again V1 vibrator points open. This process is repeated continuously, creating a "shower of sparks." (Right) Booster coil components. The booster coil is separate from the magneto and can generate a series of sparks on its own. Current flow through the primary coil sets up a magnetic field about the coil that attracts the movable contact point, breaking circuit is broken. The movable contact point then moves back to the stationary contact point via a spring. This sets up the current flow once again in a repetitive process.
|image2=Booster Coil components.png
|total_width = 440
}}
Because the magneto has low voltage output at low speed, starting an engine is more difficult.<ref name="Kroes, 1995" >{{cite book
  |last=Kroes  |first=Michael
  |title=Aircraft Powerplants
  |year=1995
  |publisher=Glencoe  |location=New York
  |page=180
}}</ref> Therefore, some magnetos have an impulse coupling, a spring-like mechanical linkage between the engine and magneto drive shaft which "winds up" and "lets go" at the proper moment for spinning the magneto shaft. The impulse coupling uses a spring, a hub cam with flyweights, and a shell.<ref name="Kroes, 1995" /> The hub of the magneto rotates while the drive shaft is held stationary, and the spring tension builds up.  When the magneto is supposed to fire, the flyweights are released by the action of the body contacting the trigger ramp. This allows the spring to unwind giving the rotating magnet a rapid rotation  and letting the magneto spin at such a speed to produce a spark.<ref name="Kroes, 1995" />