Automobile Engineering | Explain with neat sketch construction and working of starting motor.

Construction:

A starter motor consist of two major parts:

i) A stationary field 

ii) Rotating armature. 

The field is made up of number of conductor turns around the soft iron core and armature is made from a number of a number of conductor loops or windings wrapped on a laminated soft iron core which is mounted on a shaft and bearing that support it within the field. 

The conductor ends are soldered to copper commutator bars. Carbon copper compound brushes are held against the commutator bars to make electric contact between the frame and the rotating armature.

Working:

Current flows through the field and through the commutator bars into the armature winding, to develop the magnetic field around the conductors in each. 

Before the armature winding can reach its neutral point, the next set of commutator bars moves into contact with the brushes. 

This produce the same electromagnetic force on the next armature conductor. 

The rotating force of armature is transferred through the starter drive mechanism to crank the engine.

The maximum torque or turning force developed by the starter result from the strength of its magnetic field which is due to the design of the starter, winding size, and conductor size. 

In general, for more current drawn by the starter more torque will produce by the attracting and repelling of magnetic field.