Magneto is one of the special types of ignition systems with its own electric generator to provide the necessary energy for the system.
It is mounted on the engine and replaces all the components of the coil ignition system expect the spark plug.
When a magnet is rotated by the engine producing a very high voltage and it does not need a battery as a source of external energy.
Magneto can be two types :
Usually, the third type called polar induction type is also used. In this type, both the magnet and windings remain stationary but the voltage is generated by reversing the flux field with the help of soft iron polar projections is called inductors.
At first, the magnets in flywheel rotate the magneto and magnetic flux of the magnets induces a current in the primary coil by the flywheel.
A magnetic field develops around the primary coil with current flowing in the primary circuit. This magnetic field also surrounded by the secondary coil.
The flywheel continues to rotate so the breaker points open and magnetic field produced by the current in the primary winding collapses.
This collapsing magnetic field flows across the secondary coil which induces a current in the secondary coil.
There is a winding ratio in the two coils that is 60:1 so the voltage is transformed to the 10000 and 15000 volts needed to fire the spark plug.
Construction of the magneto ignition system:
It is mounted on the engine and replaces all the components of the coil ignition system expect the spark plug.
When a magnet is rotated by the engine producing a very high voltage and it does not need a battery as a source of external energy.
Magneto can be two types :
- Rotating armature type
In this type, the armature consisting of the primary and secondary windings all rotate between the poles of a stationary magnet.
- Rotating magnet type.
Usually, the third type called polar induction type is also used. In this type, both the magnet and windings remain stationary but the voltage is generated by reversing the flux field with the help of soft iron polar projections is called inductors.
Working principle of magneto ignition system:
At first, the magnets in flywheel rotate the magneto and magnetic flux of the magnets induces a current in the primary coil by the flywheel.
A magnetic field develops around the primary coil with current flowing in the primary circuit. This magnetic field also surrounded by the secondary coil.
The flywheel continues to rotate so the breaker points open and magnetic field produced by the current in the primary winding collapses.
This collapsing magnetic field flows across the secondary coil which induces a current in the secondary coil.
There is a winding ratio in the two coils that is 60:1 so the voltage is transformed to the 10000 and 15000 volts needed to fire the spark plug.
Advantages of magneto ignition system:
- Reliable for medium and high speed.
- Less maintenance.
- More effective because no battery is used.
Disadvantages of magneto ignition system:
- Starting problem issue due to low cranking speed at a starting.
- More expensive compared with the battery ignition system.
- Possibility of misfire due to leakage because wiring carries very high voltage.