Talk:Ignition coil

My jeep cherokee wont turn over i just switched starter, alternator and battery. Normally the battery register voltage when you turn the key but the gauge remains at 0 could the ignition coil cause this(----)

Principle of 'operation'

This section, added by 81.157.216.8 on 17 Sept. 2009, appears to be seriously flawed.

1. Tuned circuit?;
2. current builds up in a transfomer coil?;
3. contacts "open when the current reaches maximum"?

This all seems to be based on an innacurate understanding of the basic principles of electromagnetism that are involved here.(There may be some aspects that I don't fully understand, as applied in practice to car ignitions).

Isn't the purpose of the condensor/capacitor across the points mainly to prevent/reduce sparking of the contacts? It may function as a tuned circuit with the coil, but I dont see how it's important though it might also reduce RF interference, which sparking would create.

One might want the points to open at a time for the most powerful spark, but in this type of ignition this in mechanically controlled by the rotor opening the points. Hope I haven't been too harsh in my criticsm, but it just aint right. I'll reword it if there's no objection. --220.101.28.25 (talk) 19:37, 24 October 2009 (UTC)

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This text is also part of the intro, needs a heading if nothing else. The sections in red may be true but appear to be irrelevant to the basic principls of the system. The momentary resistance to current flow caused by the ignition coils self inductance, well, so what? Is there a tuned cct involved? You don't need one to get a high voltage at the secondary of the coil. The one across the points is in series with the coil anyway, not across it in parallel as a tuned cct requires.

Added "Principles of Operation" heading, which effectively moved text out of "íntro" section

--220.101.28.25 (talk) 21:48, 26 October 2009 (UTC)

ORIGINAL

The principle of operation is simple. When the contact breaker closes, it allows a current from the battery to build up in the primary winding of the ignition coil. (The current does not flow instantly because of the inductance of the coil.) Once the current has built up to its full level, the contact breaker opens. Since it has a capacitor connected across it, the primary winding and the capacitor form a tuned circuit, and as the stored energy oscillates between the inductor formed by the coil and the capacitor, the changing magnetic field in the core of the coil induces a much larger voltage in the secondary of the coil. More modern electronic ignition systems operate on exactly the same principle, but some rely on charging the capacitor to around 400 volts rather than charging the inductance of the coil.

EDITED

The principle of operation is simple. When the contact breaker closes, it allows a current from the battery to flow in the primary winding of the ignition coil. (The current does not flow instantly because of the inductance of the coil.) Once the magnetic field has built up in the primary, the contact breaker is opened by the rotor. Since it has a capacitor connected across it, the primary winding and the capacitor form a tuned circuit, and as the stored energy oscillates between the inductor formed by the coil and the capacitor, Current ceases flowing and the magnetic field in the primary collapses.

The collapsing magnetic field in the coil induces a much higher voltage in the secondary winding of the coil. This exits the coil via the large terminl at the top, through an insulated lead. Tnen it is sent to the sparkplugs via a rotating contact (inside the distributor) on the same rotor that opens the points. The plug leads on the ditributor take the 'spark' to the spark plugs, where it ignites the fuel in the motors cylinders.

More modern electronic ignition systems operate on exactly the same principle, but some rely on charging a the capacitor to around 400 volts rather than charging the inductance of the coil.

EDITED 2

The principle of operation is relatively simple. It applies the same laws of electro-magnetism that transformer, motors and generators use.

1. When a current flows in a wire, a magntic field surrounds the wire.
2. When a magnetic field 'cuts' a wire, a current is 'induced' in that wire.

When the contact breaker closes, it allows a current to flow in the primary winding of the ignition coil. Once the magnetic field has built up in the primary, the contact breaker is opened by the rotor. Current ceases flowing and the magnetic field in the primary collapses.

The collapsing magnetic field in the coil induces a much higher voltage in the secondary winding of the coil. This exits the coil via the large terminal at the top, through an insulated lead to the distributor. Then it is sent to the sparkplugs via a rotating contact (inside the distributor) on the same rotor that opens the points. The plug leads on the distributor take the 'spark' to the spark plugs, where it ignites the fuel in the motors cylinders.

More modern electronic ignition systems operate on similar principles, but rely on electronically charging a capacitor, whose discharge is then electronically timed, not mechanically. This ensures better control of ignition timing, which can be adjusted under electronic or computer control. This can mean better fuel economy, more power and/or less pollution under all different driving conditions.

The vast majority of ignition sytems in new vehicles are electronic/computerised sytems.

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I need to verify some of this, especailly the last 2 paragraphs. It may be a bit too detailed or wordy? Needs some work.

Readers could be referred to other articles on transformer/electromagnetism for basic principles perhap? That would shorten it a little.

From: Capacitor Discharge Ignition(CDI)

Most ignition systems used in cars are inductive ignition systems, which are solely relying on the electric inductance at the coil to produce high-voltage electricity to the spark plugs as the magnetic field breaks down when the current to the primary coil winding is disconnected (disruptive discharge).

"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. This has details that could be added in.

--220.101.28.25 (talk) 20:57, 24 October 2009 (UTC)

Further info from Ignition system - Mechanically timed ignition

Ignition system

The ignition coil consists of two transformer windings sharing a common magnetic core—the primary and secondary windings. An alternating current in the primary induces alternating magnetic field in the coil's core. Because the ignition coil's secondary has far more windings than the primary, the coil is a step-up transformer which induces a much higher voltage across the secondary windings. For an ignition coil, one end of windings of both the primary and secondary are connected together. This common point is connected to the battery (usually through a current-limiting ballast resistor). The other end of the primary is connected to the points within the distributor. The other end of the secondary is connected, via the distributor cap and rotor, to the spark plugs.

The ignition firing sequence begins with the points (or contact breaker) closed. A steady charge flows from the battery, through the current-limiting resistor, through the coil primary, across the closed breaker points and finally back to the battery. This steady current produces a magnetic field within the coil's core. This magnetic field forms the energy reservoir that will be used to drive the ignition spark.

As the engine turns, so does the cam inside the distributor. The points ride on the cam so that as the engine turns and reaches the top of the engine's compression cycle, a high point in the cam causes the breaker points to open. This breaks the primary winding's circuit and abruptly stops the current through the breaker points. Without the steady current through the points, the magnetic field generated in the coil immediately and rapidly collapses. This change in the magnetic field induces a high voltage in the coil's secondary windings.

At the same time, current exits the coil's primary winding and begins to charge up the capacitor ("condenser") that lies across the now-open breaker points. This capacitor and the coil’s primary windings form an oscillating LC circuit. This LC circuit produces a damped, oscillating current which bounces energy between the capacitor’s electric field and the ignition coil’s magnetic field. The oscillating current in the coil’s primary, which produces an oscillating magnetic field in the coil, extends the high voltage pulse at the output of the secondary windings. This high voltage thus continues beyond the time of the initial field collapse pulse. The oscillation continues until the circuit’s energy is consumed.

The ignition coil's secondary windings are connected to the distributor cap. A turning rotor, located on top of the breaker cam within the distributor cap, sequentially connects the coil's secondary windings to one of the several wires leading to each cylinder's spark plug. The extremely high voltage from the coil's secondary -– often higher than 1000 volts—causes a spark to form across the gap of the spark plug. This, in turn, ignites the compressed air-fuel mixture within the engine. It is the creation of this spark which consumes the energy that was originally stored in the ignition coil’s magnetic field. —Preceding unsigned comment added by 220.101.28.25 (talk) 11:03, 26 October 2009 (UTC)

Further data from Induction Coil

Induction coil

An induction coil or "spark coil" (archaically known as a Ruhmkorff coil after Heinrich Ruhmkorff) is a type of disruptive discharge coil. It is a type of electrical transformer used to produce high-voltage pulses from a low-voltage DC supply. To create the flux changes necessary to induce voltage in the secondary, the DC current in the primary is repeatedly interrupted by a vibrating mechanical contact called an interrupter. Developed beginning in 1836 by Nicholas Callan and others, the induction coil was the first type of transformer. —Preceding unsigned comment added by 220.101.28.25 (talk) 11:19, 26 October 2009 (UTC)

Further data from Transformer

Transformer

A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core, and thus a varying magnetic field through the secondary winding. This varying magnetic field induces a varying electromotive force (EMF) or "voltage" in the secondary winding. This effect is called mutual induction. —Preceding unsigned comment added by 220.101.28.25 (talk) 13:40, 26 October 2009 (UTC)

Further data from : Autotransformer

Autotransformer

An autotransformer (sometimes called autoformer)is an electrical transformer with only one winding. The winding has at least three electrical connection points called taps. The voltage source and the load are each connected to two taps. One tap at the end of the winding is a common connection to both circuits (source and load). Each tap corresponds to a different source or load voltage. In an autotransformer a portion of the same winding acts as part of both the primary and secondary winding. —Preceding unsigned comment added by 220.101.28.25 (talk) 13:44, 26 October 2009 (UTC)

Is an ignition coil an 'autoransformer'?. Does it have 2 seperate windings? If so then, technically, it is NOT an autoransformer. But several related articles say YES. —Preceding unsigned comment added by 220.101.28.25 (talk) 21:59, 26 October 2009 (UTC)

Principles of Operation 3 (adding relevent information from 'Transformer' etc)

The 'Ignition system' article has a better description of how the Ignition coil works than the 'Ignition coil' article does! IMHO

I intend to re-write 'Ignition coil' to include the relevant info from other article(s) so the coils operational principles are described much better.

The info in 'Igniton system' could then be re-written to show how the ENTIRE system works without need in to go into (even repeat) basic principles. Readers can refer to the other articles ie. Distributor, Spark plug, condensor, mutual induction, magnetism. etc (via links)for more detailed information.

There are schematic diagrams of the ignition system so one of these should be put into the article.

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EDITED Version 3

The principle of operation is relatively simple. It applies the same basic laws of electro-magnetism that motors, generators and particularly transformers use. see Magnetism, Transformer, Faradays laws.

• When a current flows in a wire, a magnetic field bulds up and surrounds the wire.
• When a magnetic field 'cuts' a wire, a current is 'induced' in that wire.
• When the current in a wire ceases, the magnetic field around the wire collapses.

The ignition coil is merely an electrical transformer used to produce high-voltage pulses from a low-voltage DC supply. It consists of two transformer windings sharing a common magnetic core—the primary and secondary windings

A current in the primary induces a magnetic field in the coil's core. (see Mutual induction) Because the ignition coil's secondary has far more windings than the primary, the coil is a step-up transformer which induces a much higher voltage across the secondary windings.

To create the flux changes necessary to induce voltage in the secondary, the DC current in the primary is repeatedly interrupted.

When the contact breaker closes, it allows a current to flow in the primary winding of the ignition coil. Once the magnetic field has built up in the primary, the contact breaker is opened by the rotor. Current ceases flowing and the magnetic field in the primary collapses.

The collapsing magnetic field in the coil induces a much higher voltage in the secondary winding of the coil. This exits the coil via the large terminal at the top, through an insulated lead to the distributor. Then it is sent to the sparkplugs via a rotating contact (inside the distributor) on the same rotor that opens the points. The plug leads on the distributor take the 'spark' to the spark plugs, where it ignites the fuel in the motors cylinders.

More modern electronic ignition systems operate on similar principles, but rely on electronically charging a capacitor, whose discharge is then electronically timed, not mechanically. This ensures better control of ignition timing, which can be adjusted under electronic or computer control. This can mean better fuel economy, more power and/or less pollution under all different driving conditions.

The vast majority of ignition systems in new vehicles are electronic/computerised sytems.

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Igntion circuits schematic (appears to show basic &improved cct)

• http://commons.wikimedia.org/wiki/File:Basic_ignition_coil_circuits.svg

--220.101.28.25 (talk) 15:46, 28 October 2009 (UTC)

Can't believe no none found all the errors on this page. The purpose of the condenser(capacitor) is to prolong the life of the breaker points by reducing arcing, it's NOT a tuned circuit component. The function of the ballast(series) resistor is to limit CURRENT, not voltage, in the primary coil winding at low speeds or when the engine is stopped with the ignition energized(key in "run" position) and the points closed. — Preceding unsigned comment added by 68.205.179.7 (talk) 01:14, 2 January 2012 (UTC)

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In the introduction :

"Some coils have an internal resistor to reduce the voltage and some rely on a resistor wire or an external resistor to reduce the voltage from the car's 12 volt wiring flowing into the coil."

Hmm aren't the resistors there to limit the current flowing into the coils and avoiding overheating / burning them rather than decreasing voltage, which I think is useless and counter productive in the case of a voltage amplifier coil arrangement ?

Woops sorry didn't saw it was already posted ;)