What is the working principle of a starter motor?

[Carol]

The working principle of a starter motor is to provide external support for the engine during startup. Generally, the starter motor utilizes the following three components to achieve the entire starting process. The DC motor draws current from the battery and enables mechanical movement of the starter's drive gear. The transmission mechanism engages the drive gear with the flywheel ring gear while automatically disengaging from the starter circuit after engine startup. The on/off operation of the starter circuit is controlled by an electromagnetic switch. When the ignition switch is turned off, the holding coil (S-ground) and the pull-in coil (S-M) are powered through terminal M. At this point, the magnetic field generated by the pull-in coil (S-M) is opposite to that during initial startup and counteracts the magnetic field of the holding coil (S-ground). The resultant force from these two magnetic fields causes the iron core to return to its original position, disconnecting the main contacts B and M. This cuts off the DC motor's circuit, causing it to decelerate and stop.