Starter Motor, How They Work(Armature&Commutator)

Starter Motor

How They Work(Armature&Commutator)

The armature

This sits in a field housing(or body-yoke).There are two types of field housing; one with permanent magnets, the other with field coils which are wound around ‘pole shoes’. These pole shoes only become magnetised when a current flows around them.


Most field coil windings can be replaced-although they are often hard to remove because the pole shoe screws are normally very tight indeed. The permanent magnet version suffers more from un-stuck magnets(which can be stuck back)-but don’t turn them round. Broken magnets are normally caused by being tapped with a hammer.


The commutator

Usually at the back of the armature is the commutator. The brushes bear directly on this to transfer the electrical current to and from the armature.