The starter system functions as the engine starting system in the vehicle. A starter system is needed for vehicles because a car or motorbike engine cannot start by itself, but needs initial power to trigger the first combustion.
In general, there are two types of starter systems, namely;
- Mechanical starter system, this uses human power to rotate the engine crankshaft, for example the kick starter on a motorbike.
- Electric starter system, this uses an electric motor to rotate the crankshaft so we just press the start button.
Electric starter systems are now used in almost all types of vehicles, especially cars. Therefore, in this article we will only discuss how the electric starter system works in vehicles.
Working Principle of Electric Starter
The electric starter system uses the help of an electric motor to rotate the crankshaft. The working principle is that an electric motor will be placed next to the flywheel which has gears.
Then an electrical circuit will be connected from the battery to the starter motor. So, when the circuit is activated the starter motor will rotate and trigger the first combustion in the engine.
Electric starter circuit components
- The battery functions as a source of electric current
- The relay functions to bridge the current from the battery directly to the motor without passing through a switch
- Fuse functions as a circuit protector to avoid excess electric current
- The starter switch functions as a button to activate the electric starter circuit
- The starter solenoid/starter clutch functions to connect and disconnect the gears between the electric motor and the flywheel.
- The starter motor functions as a converter of incoming electrical energy into rotational energy using electromagnetic principles.
How the Electric Starter Circuit Works
The electric starter system does not continue to rotate, but this system automatically stops when the engine is running.
Therefore, in the starter system there is a starter clutch which functions to connect the starter gear when turning the flywheel and disconnect the starter gear when the engine has successfully started.
How does it work ?
1. In the Off position (ignition key Off/On)
When the starter circuit is off, the electrical circuit will be disconnected at the relay section. Currently, there is an electrical path from the battery, entering terminal 85 relay then leaving output 86 relay and stopping at the switch without reaching the mass.
As a result, the flow of electricity will not occur so that terminals 30 and 87 on the relay will not be connected. Because these two terminals are not connected, electric current from the battery will not flow to the starter motor.
2. When the ignition key is turned to ST
When we turn the key to ST, the switch will connect electric current to the mass. So, there will be an electric current from the battery, entering terminal 85 of the relay, passing through the coil in the relay, coming out of terminal 86 of the relay, going to the switch and reaching the negative of the battery.
Inside the relay, there is a coil which, when electrified, creates a magnetic force. This magnetism will attract the metal plate located above the coil. When the plate is attracted the result is that terminals 30 and 87 of the relay will be connected.
This will cause electricity to flow in another path, the path is from the battery, into the fuse, into terminal 30 of the relay, out of terminal 87 of the relay, into the starter clutch, and up to the starter motor. So that the starter motor rotates.
Electrical circuit in the starter motor
Maybe the question has crossed your mind, how can the starter motor turn the crankshaft?
In a starter motor, there are two main components, namely the starter switch and the electric motor. The current from the starter relay first enters the starter switch before entering the motor.
There are three terminals on the starter switch, namely;
- Terminal 50, where the electric current enters from the starter relay
- Terminal 30, where the large current enters without a relay directly from the positive battery terminal
- Terminal C, current output from the starter switch which is connected to the starter motor.
The current from the starter relay first enters terminal 50 of the starter switch, then the electric current will pass through the pull in coil and hold in coil. These two coils will produce strong magnetism when an electric current flows through them. This magnetism will move the iron core in the coil to connect the starter pinion gear to connect it to the flywheel.
Apart from that, the movement of the iron core will also move a plate in the starter switch to connect terminal 50 and terminal C.
As a result, the large current that is already standing by at terminal 30 will flow directly into the starter motor via terminal C. This is what makes the starter motor rotate.
3. When the key is in the ON position and the engine is running
When the engine starts successfully, we automatically release pressure on the starter button. This will make the current at terminal 50 on the starter switch disappear because the starter relay is disconnected.
As a result, the hold coil and pull in coil also lose electric current, this will make the iron core return to its previous position.
The return of the iron core in the starter switch will make a connection between terminal 50 and terminal C, apart from that, the return of this iron core will also break the connection between the starter gear pinion and the flywheel. So even if the flywheel is spinning fast, the starter motor will not be affected.
That’s the article about how the starter system works on cars and motorbikes. Hopefully it can broaden our insight.
