# In the DC machine, the fractional pitch winding is used

In the DC machine, the fractional pitch winding is used

### Right Answer is:

To reduce the Harmonic in generated EMF

#### SOLUTION

- In full pitched coils, as one conductor of a turn in a coil cuts N pole, the other conductor of the same turn cuts S pole resulting in the production of induced emf(E), i.e phase angle is 180 degree
- In short-pitched coils, both conductors of the same turn in a coil don’t cut the respective poles simultaneously. so phase angle is slightly less than 180 degree As a result, the magnitude of induced emf gets reduced to E × Cos(nα/2)

Where**E × Cos(nα/2) is called a pitch factor**

For eliminating 3^{rd }harmonic from Generated EMF,

Cos(3α/2) = 0

3α/2 = π/2

** α = π/3 = 60°**