Low tension coil
   HOME

TheInfoList



OR:

A low tension coil is an electrical device used to create a
spark Spark commonly refers to: * Spark (fire), a small glowing particle or ember * Electric spark, a form of electrical discharge Spark may also refer to: Places * Spark Point, a rocky point in the South Shetland Islands People * Spark (surname) * ...
across the points of an
ignitor Ignitor is the Italian name for a planned tokamak device, developed by ENEA. , the device has not been constructed. Started in 1977 by Prof. Bruno Coppi at MIT, Ignitor based on the 1970s Alcator machine at MIT which pioneered the high magnetic ...
on early 1900s
gasoline Gasoline (; ) or petrol (; ) (see ) is a transparent, petroleum-derived flammable liquid that is used primarily as a fuel in most spark-ignited internal combustion engines (also known as petrol engines). It consists mostly of organic co ...
engines, generally
flywheel engine A reciprocating engine, also often known as a piston engine, is typically a heat engine that uses one or more reciprocating pistons to convert high temperature and high pressure into a rotating motion. This article describes the common featu ...
s,
hit and miss engine A hit-and-miss engine or Hit 'N' Miss is a type of stationary internal combustion engine that is controlled by a governor to only fire at a set speed. They are usually 4-stroke but 2-stroke versions were made. It was conceived in the late 19th c ...
s, and other engines of that era. In modern electronic terms, a low tension coil is simply a large
inductor An inductor, also called a coil, choke, or reactor, is a passive two-terminal electrical component that stores energy in a magnetic field when electric current flows through it. An inductor typically consists of an insulated wire wound into a c ...
, an electrical device that stores energy for brief periods. The term "low tension" was the terminology of the day used to differentiate it from the term "high tension", and generally meant "low voltage" (tension) as opposed to "high voltage" (tension). High tension coils produce high voltages, generally meant to produce a spark across a spark plug.


Construction

A low tension coil consists of an iron core that has wire wrapped around it. The size of the iron core, the number of turns of wire, and the size of the wire determine the electrical properties of the coil. Terminals are provided to connect the coil into the ignition circuit. The wood ends are provided for mechanical stability, to provide for the terminal placement and to hold the wire on the coil over time. A cloth or tape covering is provided to protect the windings. The iron core should be a bundle of thinly insulated iron wires, or flat thin sheets like those in a transformer, to prevent losses and heating from current that would be induced in a solid rod.


Use

A low tension coil for engine ignition is used in conjunction with a battery and an ignitor. The ignitor is no more than a set of contacts that reside inside the combustion chamber of the engine. A series circuit is made between the three components: battery connects to coil, second terminal on the coil connects to the ignitor, second terminal on the ignitor (usually connected electrically and mechanically to the engine itself) connects to the second terminal of the battery.


Multi-cylinder engines

The low tension coil system was also used for multi-cylinder engines, although rarely, as it required a separate coil for each cylinder.


Theory of Operation

An inductor attempts to maintain a constant current flow through it. If the current in the circuit in which the inductor is connected goes down for some reason, the voltage developed across the inductor will go up in an attempt to try to maintain the constant current. When used with an ignitor ignition system in an engine, there is current flow when the ignitor contacts are closed. When the ignitor contacts are opened by the mechanical parts of the engine, current flow is interrupted. Because the low tension coil wants to maintain that current flow, the voltage across the coil rapidly goes up (usually to several hundred volts). When the voltage rises high enough, the voltage will jump the still very small gap of the ignitor contacts and create a spark which ignites the fuel mixture in the engine. Since there is a finite amount of energy stored in the coil, as soon as the spark jumps the gap the voltage across the coil collapses. As soon as the engine rotates and the ignitor contacts again close, current starts to flow through the coil and it again stores energy for the next cycle. A good description and moving gif of a low tension coil in operation can be found o
Harrys Old Engines Ignition Page


See also

*
Ignition coil An ignition coil (also called a spark coil) is an induction coil in an automobile's ignition system that transforms the battery's voltage to the thousands of volts needed to create an electric spark in the spark plugs to ignite the fuel. So ...
*
Inductor An inductor, also called a coil, choke, or reactor, is a passive two-terminal electrical component that stores energy in a magnetic field when electric current flows through it. An inductor typically consists of an insulated wire wound into a c ...
*
Induction coil An induction coil or "spark coil" (archaically known as an inductorium or Ruhmkorff coil after Heinrich Rühmkorff) is a type of electrical transformer used to produce high-voltage pulses from a low-voltage direct current (DC) supply. p.98 To ...
*
Trembler coil A trembler coil, buzz coil or vibrator coil is a type of high-voltage ignition coil used in the ignition system of early automobiles, most notably the Benz Patent-Motorwagen and the Ford Model T. Its distinguishing feature is a vibrating magnetica ...


External links


Harrys Old Engines Ignition Page
{{DEFAULTSORT:Low Tension Coil Electromagnetic coils Ignition systems