Magneto ignition is a special type of 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. 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.
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. 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.
Today you’ll get to know the definition, functions, applications, components, diagram, and workings of the magneto ignition system. you’ll also get to know the advantages and disadvantages of the offer to spark-ignition engines.
Contents
Magneto ignition system definition
A magneto ignition system or high-tension magneto is an ignition system that uses 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.
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 winding 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 which powers the spark plug that further ignites the fuel-air mixture in the combustion chamber. another function of the magneto system is performed by the spark plug as heat can dissipate through the system. the system also causes ionization to be measured in the cylinders.
Design 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. The primary coil’s leakage inductance stores energy, which is absorbed by a capacitor positioned across the points. 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 turns ratio is the number of turns in the secondary winding divided by the number of turns in the primary winding. A proportionate voltage is induced across the secondary winding of the coil as a result of the voltage across the primary coil.
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.
- Finally, the magneto ignition system is widely used in applications such as tractors, outboard motors, washing machines, marine engines, power units, and natural gas engines.
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’s typically a small generator that works on electricity as it produces a voltage when rotated by the engine. This is to say, that the higher the rotation, the greater the voltage produced by the system. 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.
Read: Understanding the working of the Battery ignition system
In the gap type distributors, the electrode of the rotor arm is close to the distributor cap but is 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.
Spark plug:
The spark plug is a device that is powered by the ignition system to ignite 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 magnet.
Contact breaker:
This contact breaker is regulated by the cam, which allows current to flow through the capacitor and charges it when the breaker is open.
Ignition switch:
The ignition switch helps to start and off the vehicle ignition system. it controls and sets the parallel of the capacitor because it helps to prevent damage from too much air.
magneto ignition system diagram:
Working principle
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 parallelly. 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. When the speed of the engine is low at the starting stage, the voltage generated by the magneto is also low. But as soon as the rotating speed of the engine increases, the voltage generated also increases. If this happens, the flow of the current is also increased.
Read: Understanding transistorized ignition system
Watch the video on the working of the magneto ignition system:
Advantages and disadvantages of the magneto ignition system
Advantages:
Below are the benefits of the magneto ignition system in its various applications:
- Less maintenance is required compared to the battery ignition system.
- Less cost as the battery is not used.
- Efficient working due to high-intensity spark.
- The electric circuit is generated by the magneto.
- It occupies less space.
- Since the battery is not used, there are no issues with battery discharge or battery error.
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Disadvantages:
Despite the good advantages of the magneto ignition system, some limitations still occur. Below are the disadvantages of the system in various applications:
- Poor quality of spark due to low speed at first start.
- Misfiring may occur due to leakage. This is because the variation of voltage in the wiring can occur.
- The system is more expensive compared to other types of ignition systems.
Read more: Things you need to know about Turbocharged Engines
In conclusion, a magneto ignition system is a great development on spark-ignition engines and other internal combustion equipment. We have looked in-depth at the definition, function, and components of the ignition system. we also covered its working, as well as its advantages and disadvantages where we said it requires less maintenance and no battery is employed. We also saw that it provides poor quality spark at first start because of the low speed it experiences.
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