Magneto ignition is a special ignition system that provides a spark in spark-ignition engines, such as petrol engines. it is used to obtain pulses of high voltage for the spark plugs.
Internal combustion engines use magneto ignition systems to provide the high-voltage electrical sparks required to ignite the fuel-air combination in the engine’s cylinders. The system has been in existence for over 100 years and is still used today on stationary and portable engines. It’s mostly employed in applications where space for the external battery is restricted.
Well, in this reading, we’ll explore what a magneto ignition system is, its applications, parts, construction, diagram, and how it works. We’ll also explore its advantages and disadvantages.
Let’s get started!
Learn about ignition system with this detailed guide!
What is a Magneto Ignition System?
A magneto ignition system, or high-tension magneto, is an ignition system that uses a magneto to create high voltage for the generation of electricity. The electricity generated is further used to run vehicles and other electrical components in the system.
The magneto is a combination of a distributor and generator built as one unit, making it different from the conventional distributor that creates spark energy without external voltage.
Light engines, including those used in motorcycles, automobiles, light airplanes, and likely older cars, frequently use this ignition method. It is known for its dependability and capacity to function without any kind of additional power sources like batteries or alternators.
There is a series of rotating magnets that break an electrical field, causing an electrical current in the coil’s primary winding. The current charge will then multiply when it transfers to the coil’s secondary winding.
This is because there are many more times the number of windings in the secondary circuit compared with the one in the primary circuit, which then causes the multiplied charge magneto to produce a spark at a higher voltage than was created in the primary winding.
In most cases, a magneto system can produce a voltage as high as 20,000, which results in a very hot spark that a conventional distributor can produce. The function of a magneto system is to use a magneto to provide current for the ignition system.
This current is used to power the spark plug that further ignites the fuel-air mixture in the combustion chamber. The spark plug serves another purpose in the magneto system because heat can dissipate through the system. The system also causes ionization to be measured in the cylinders.
Application of Magneto Ignition System
Below is the application of magneto ignition in various aspects as it generates the electricity needed for ignition:
The system is used in two-wheeler vehicles (SI engines). Just as the battery is used to generate power in the battery ignition system, magneto is used for the generation of electricity.
The magneto ignition system is widely used in applications such as tractors, outboard motors, washing machines, marine engines, power units, and natural gas engines.
Magneto ignition systems are used in small engines like lawnmowers, chainsaws, and generators due to their reliability and independence from external power sources. In aircraft, magneto ignition systems are used to ensure consistency and efficient ignition in flight operations.
Just as mentioned earlier, older vehicles and motorcycles use magneto ignition systems because of their simplicity and historical benefits. Also, in marine engines, magneto ignition systems are used to provide reliability, often in ships and boats.
Most stationary engines used in various industrial and commercial applications use magneto ignition. A robust off-road motorcycle uses a magneto ignition system for storing ignition capabilities. Agricultural equipment like tractors and harvesters uses magneto ignition for efficient operations during farming.
You should also learn about Electronic Ignition System with this detailed guide!
Components of the Magneto Ignition System
Below are the functional components that aid the working of magneto ignition systems in various applications:
Magneto:
The magneto is the source of energy generation in the magneto ignition system. It typically is a small generator that runs on electricity because the engine rotates it, creating a voltage.
That is to say, the system produces more voltage the higher the rotation. The system has no external source of energy and does not need one to start it; the magneto itself is a source for generating energy. The winding in the system is of two types, which include primary binding and secondary binding.
Depending on the engine rotation, the magneto is of three types:
- Magnet rotating type
- Armature rotating type
- Polar inductor type
The difference between the three is just their source of rotation. In the magnet type, the armature is stationary while the magnets rotate around the armature. Whereas in the armature type, the armature rotates between the stationary magnet.
Finally, in the polar inductor type, both the magnet and the winding remain stationary, but the voltage is generated when the flux field is reversing. This is achieved with the help of soft iron polar projections, which are known as inductors.
Distributor:
The distributor components used in the magneto ignition system can also be found in the multi-cylinder engine. These multi-cylinder engines are used for the regulation of spark in the right sequence in the spark plug. It causes the surge of the ignition to be distributed uniformly among the spark plugs.
Distributors are of two types, which include
- Gap type, and
- Carbon brush-type distributor.
In the gap-type distributors, the electrode of the rotor arm is close to the distributor cap but is not in contact. This eliminates the occurrence of wear in the electrode.
In the carbon brush type, the rotor arm sliding over the metallic segment carries the carbon brush that is placed inside the distributor cap or molded insulating material. With this, an electric connection is created with the spark plug.
Learn about battery ignition system with this detailed guide!
Spark plug:
The ignition system powers the spark plug, which is a device that ignites the fuel-air mixture in the cylinder. It has two electrodes that are parted from each other, which allow a high voltage to flow through it.
These electrodes are made of a steel shell and an insulator. The central electrode is attached to the supply of the ignition coil and an outer steel shell. It’s grounded, insulating them.
Capacitor:
A capacitor is also a component in the magneto ignition system. it’s just like the conventional electrical capacitor with two metal plates separated by an insulating material at a distance.
Air is commonly used as insulating material on this system, but to reach a particular technical requirement, a high-quality insulating material is employed. The function of this capacitor is to store charge.
Cam:
The cam is attached to the north and south magnets.
Contact breaker:
The cam controls this contact breaker, allowing current to flow through the capacitor and charging it when the breaker is open.
Ignition Switch:
The ignition switch helps to start and turn off the vehicle’s ignition system. It controls and sets the parallel of the capacitor because it helps to prevent damage from too much air.
Diagram
You should also learn about Ignition Relay with this detailed guide!
Design and Construction of Magneto Ignition System
Simple magnetos (permanent magnet electrical generators) can generate relatively low-voltage electricity, but they are unable to generate the high voltages needed by spark plugs found in the majority of modern engines (apart from diesel engines).
An electrical transformer is also a component of an ignition magneto, and it converts electricity to a greater voltage at the expense of a proportional decrease in output current.
The point spacing initially causes the voltage across the primary coil to arc across the points when the points start to open. A capacitor located across the points absorbs the energy that the primary coil’s leakage inductance stores. This capacitor also reduces the primary winding voltage’s rising time, allowing the points to fully open.
An electrical transformer is created by winding a secondary coil—with many more turns than the primary—onto the same iron core. The turn ratio is equal to the sum of the turns in the primary winding and the secondary winding.
A proportionate voltage is induced across the secondary winding of the coil as a result of the voltage across the primary coil.
How Does Magneto Ignition Work?
The working of a magneto ignition system is less complex and can be easily understood. Its working begins when the engine of the system starts working and then rotates the magneto. The magneto then creates the energy of high voltage.
The end of the magneto is grounded at one end through a contact breaker, and the capacitor is attached to it in parallel. The cam helps to regulate the contact breaker and current flow through the capacitor and charges it when the breaker is open.
With that, the capacitor acts as a charger as the primary current flow is reduced, and then the overall magnetic field is reduced in the system. This increases the voltage in the capacitor, which acts as an EMF, thus producing the spark.
This is achieved with the help of the distributor. At startup, the magneto’s voltage output is also low because the engine speed is low. But as soon as the rotating speed of the engine increases, the voltage generated also increases. The flow of the current also increases.
Learn about car charging system with this detailed guide!
Advantages and Disadvantages of Magneto Ignition System
Advantages:
- Increased reliability: eliminates reliance on external power sources.
- Independent Operation: Doesn’t require a battery to start the engine.
- Suitability for High Engine Speeds: Suitable for medium- to very high-speed engines.
- Compact and Lightweight Design: Uses cobalt steel and nickel aluminum magnet metals.
- Low Starting Speed Ignition: Modern magnet alloys improve low starting speed ignition.
- Precision Automatic Timing: Enables easy and accurate automatic ignition timing.
- Prevention of Spark Plug Damage: Prevents electrode burning in spark plugs.
Disadvantages:
- Inferior Sparks for Low-Speed Starting: May produce weaker sparks at low engine speeds.
- Higher Manufacturing and Replacement Costs: More expensive to manufacture and replace component parts.
- Complex Half-Speed Engine Driver: More complex than a coil ignition system.
- Impact on Ignition Timing Range: Adjusting spark timing can influence voltage or energy produced.
- Challenged Maintenance: More cumbersome and less user-friendly than other ignition systems.
Conclusion
The Magneto Ignition System is a reliable and compact ignition setup commonly used in small engines, motorcycles, and aircraft engines, where battery dependence is undesirable.
It generates its own electrical power using a magnet, removing the need for an external battery. Though largely replaced by modern electronic ignition systems in cars, it remains vital in areas where simplicity, low maintenance, and self-sufficiency are key.
You should also learn about multi-point fuel injection system with this detailed guide!
FAQs on Magneto Ignition System
What is a magneto ignition system?
It’s an ignition system that generates high voltage using a permanent magnet and a coil, without needing a battery.
Where is the magneto ignition system used?
- Motorcycles
- Scooters
- Lawnmowers
- Small aircraft
- Stationary engines
What are the main components of a magneto ignition system?
- Magneto (rotating magnet and coil)
- Breaker points (contact points)
- Capacitor (condenser)
- Spark plug
- How does the magneto ignition system work?
When the magnet rotates, it induces a voltage in the coil. When the contact breaker opens, it causes a rapid collapse in the magnetic field, generating a high voltage that fires the spark plug.
What are the advantages of a magneto ignition system?
- No battery required
- Compact and self-contained
- Durable and reliable
What are the disadvantages?
- Produces weaker spark at low speeds
- Can be hard to start in cold conditions
- Not suitable for high-performance engines
How is it different from a battery ignition system?
The magneto system doesn’t require a battery and generates power itself, while the battery ignition system depends on the vehicle’s battery and alternator for spark generation.