Section through a high-tension magneto, with distributorAn ignition magneto, or high tension magneto, is a that provides current for the of a, such as a. It produces pulses of for the. The older term tension means.The use of ignition magnetos is now confined mainly to engines where there is no other available electrical supply, for example in. It is also widely used in piston engines even though an electrical supply is usually available.
In this case the magneto's self-powered operation is considered to offer increased reliability; in theory the magneto should continue operation as long as the engine is turning. Contents.History Firing the gap of a, particularly in the combustion chamber of a high-compression engine, requires a greater voltage (or higher tension) than can be achieved by a simple magneto. The high-tension magneto combines an alternating current magneto generator and a. A high current at low voltage is generated by the magneto, then transformed to a high voltage (even though this is now a far smaller current) by the transformer.The first person to develop the idea of a high-tension magneto was, but his design omitted a condenser ; in partnership with were the first to develop a practical high-tension magneto.Magneto ignition was introduced on the 1899. This was followed by, and, and soon was used on most cars up until about 1918 in both low voltage (voltage for secondary coils to fire the spark plugs) and high voltage magnetos (to fire the spark plug directly, similar to ignitions, introduced by Bosch in 1903). Operation In the type known as a shuttle magneto, the engine rotates a coil of wire between the poles of a. In the inductor magneto, the is rotated and the coil remains stationary.As the magnet moves with respect to the coil, the of the coil changes.
Magneto is the god of magnets, who created the Field around the earth to protect those who inhabited it. But in doing this, he turned mortal and inhabited the body of a human, who is now.
This induces an in the coil, which in turn causes a to flow. One or more times per revolution, just as the magnet pole moves away from the coil and the magnetic flux begins to decrease, a opens the and interrupts the current. This causes the in the primary coil to collapse rapidly. As the field collapses rapidly there is a large voltage induced (as described by ) across the primary coil.As the points begin to open, point spacing is initially such that the voltage across the primary coil would arc across the points. A is placed across the points which absorbs the energy stored in the of the primary coil, and slows the rise time of the primary winding voltage to allow the points to open fully.
The capacitor's function is similar to that of a as found in a.A second coil, with many more turns than the primary, is wound on the same iron core to form an electrical. 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, 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.The capacitor and the coil together form a which allows the energy to oscillate from the capacitor to the coil and back again. Due to the inevitable losses in the system, this oscillation decays fairly rapidly. This dissipates the energy that was stored in the condenser in time for the next closure of the points, leaving the condenser discharged and ready to repeat the cycle.On more advanced magnetos the cam ring can be rotated by an external linkage to alter the ignition timing.In a modern installation, the magneto only has a single low tension winding which is connected to an external which not only has a low tension winding, but also a secondary winding of many thousands of turns to deliver the high voltage required for the spark plug(s). Such a system is known as an 'energy transfer' ignition system. Initially this was done because it was easier to provide good insulation for the secondary winding of an external coil than it was in a coil buried in the construction of the magneto (early magnetos had the coil assembly externally to the rotating parts to make them easier to insulate—at the expense of efficiency).
Selimo Romeo Bottone (1907). Magnetos for Automobilists, how Made and how Used: A Handbook of Practical Instruction in the Manufacture and Adaptation of the Magneto to the Needs of the Motorist. Lockwood and son. ^ Cauldwell, O. Aero Engines: for Pilots and Ground Engineers. P. 88.
London: Grange-Universal. ^. From the original on 2015-09-18. Retrieved 2016-06-21. CS1 maint: Archived copy as title. From the original on 9 July 2017.
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Small-block Chevy performance: modifications and dyno-tested combinations for high performance street and racing use.
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The initial spin of the crank comes from the starter or hand propping or compressed air or inertial starter (or one of a bunch of other starting systems)One old system used by the Germans in wwI I think the pilot or ground crew would put the engine just a little passed top dead center, with one mag fully retarded, then that mag was advanced until it fired starting the engine.