Short pitched coils are deliberately used in an alternator, because:

Concept:

Advantages of Short Pitch Coil:

• Reduces the amount of copper needed for End Connection when compared with Full Pitched Coil.
• Improves the waveform of generated EMF i.e. generated EMF can be made to approximate to a sine wave more easily and the distorting harmonics can be reduced or eliminated.
• Eddy current and hysteresis losses are reduced.

Additional Information

Coil pitch or coil span: It is defined as the angular distance between the two coil sides of one coil. It is expressed in terms of electrical space degree.

Full pitch winding	Short pitch winding
The angular distance between the two coil sides is one pole pitch, it is called a full pitch coil.	The angular distance between the two coil sides is less than one pole pitch, it is termed short pitch or fractional pitch coil.
The coil span equal to 180 electrical degrees	The coil span is less than 180 electrical degrees Here ξ is the chorded angle or short pitch angle.