What is Magneto Ignition System?- Parts & Working

Technologically speaking, one of the oldest components on general aviation aircraft is the magneto, a technology that is more than 100 years old. The magneto is a self-contained generator of high voltage that provides ignition to an engine through spark plugs. A magnet—hence magneto—spins in close proximity to a coil of wire.

As the magnet spins (or the magnet rotor is turned), it generates a strong magnetic force that is “held back” by a primary coil. The moment the contact points open, a rapid magnetic flow generates a high voltage in the secondary coil, which ignites the spark plug, thus firing the engine.

The two magnetos on most GA aircraft—the left and the right—each fire one of two spark plugs on each cylinder. There are two magnetos so that if one fails the engine continues to run, but will be less efficient.

Magneto ignition systems are used primarily in lawn motors, chain saws, and old tractors; they have remained a source of power in light aircraft because they are self-contained and not attached to battery or electric systems in the aircraft, allowing the engine to continue to run even during a battery or electrical failure.

What is Magneto Ignition System?

A magneto ignition is an older types of ignition system used in spark-ignition engines (such as petrol engines). It uses a magneto and a transformer to make pulses of high voltage for the spark plugs. The older term “high-tension” means “high voltage”.

A simple magneto 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. An ignition magneto also includes an electrical transformer, which converts the electricity to a higher voltage.

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.

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. The 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.

Parts of Magneto Ignition System

These are the main parts of Magneto Ignition Systems:

• Transformer core
• Contact Breaker
• Cam
• Capacitor
• Ignition Switch
• Distributor
• Spark Plug

1. Transformer core

The main part of the magneto-ignition system is the transformer core, which consists of two types of windings.

One is the primary winding and the other is the secondary winding. The primary winding is also referred to as the low-voltage winding and the secondary winding as the high-voltage winding.

One end of the primary winding is grounded and the other end is connected to the connection, the contact breaker, and the capacitor.

2. Contact Breaker

The contact breaker is regulated by the cam and when the breaker is open, current flows through the capacitor and charges it. It is generally used for making and breaking the Primary circuit. The pivoted arm(link) has a heel attached in the middle which breaks the contact point due to the action of a cam.

3. Cam

One end of the shaft is connected to the cam and the other end is connected to the magnet which has two poles, North and South.

4. Capacitor

The main job of the capacitor is to store the charger. The capacitor used here is a simple electrical capacitor. One end is connected with the primary winding and the other end is grounded and it is generally used to store the charge coming from the primary winding.

5. Ignition switch

Works for off and on vehicles and this is set to the parallel of the capacitor because it helps to avoid the damage of excessive air.

6. Distributor

A distributor is provided for distributing the ignition surges to individual spark plugs in the correct sequence with respect to the firing order. It consists of the rotor in the middle and the metallic electrode on the periphery.

These metallic electrodes are directly connected to the spark plugs and are also known as the Ignition harness. As the rotor rotates, it passes the high-tension current to the ignition harness which then carried these high-tension currents to the spark plugs.

7. Spark Plug

Spark Plug is the last component of the Magneto Ignition System. It consists of 2 electrodes, one attached to the high-tension current-carrying wires, and the other is grounded.

The potential difference between these electrodes ionizes the gap present between them and thus a Spark is generated which ignites the combustible mixture.

Magneto Ignition System Diagram

How does a magneto ignition system work?

The magneto is a self-contained generator of high voltage that provides ignition to an engine through spark plugs. The moment the contact points open, a rapid magnetic flow generates a high voltage in the secondary coil, which ignites the spark plug, thus firing the engine

Magneto is used in the magneto ignition systems. When the engine starts, it helps the magnet rotate, thus generating energy in the form of high voltage. Then one end of the magnet is grounded via a contact switch and the ignition capacitor is connected to its parallel.

The contact breaker is controlled by the cam. When the switch is open, current flows through the capacitor and charges it.

Now the capacitor acts as a charger, the primary current flow is reduced, which reduces the overall magnetic field generated in the system.

This increases the voltage in the capacitor. This increased high voltage in the capacitor acts as an EMF and thus creates the spark on the right spark plug through the distributor.

And in the starting phase, the speed of the engine is low and therefore the voltage generated by the magneto is low.

However, as the engine speed increases, so does the voltage generated by the magneto, which also increases the flow of current.

Applications of Magneto Ignition System

The Magneto Ignition Systems used in:

• This system is used to produce electricity (a battery system uses its battery) and to run vehicles.
• This is mainly used in two-wheeled vehicles today.
• A rotating magnet generates high voltage.
• This is also used in various places such as buses, power units, marine engines, tractors, outboard engines, washing machines, and natural gas engines.

Advantages of Magneto Ignition System

These are the advantages of Magneto Ignition Systems:

• This magneto ignition system requires less maintenance compared to the battery ignition system.
• This is more useful because it does not use a battery.
• It takes up less space.
• The magnet creates a circuit
• No battery is required, so there is no problem with battery discharge
• The efficiency is improved by high-intensity sparks.

Disadvantages of Magneto Ignition System

However there are some disadvantages:

• It has a starting problem due to the low RPM when starting the engine.
• It’s more expensive than a battery ignition system.
• There is a possibility of a misfire due to leakage as voltage fluctuations in the wiring can occur.

How does a Magneto ignition system work?

FAQs.