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 3rd harmonic from Generated EMF,
Cos(3α/2) = 0
3α/2 = π/2
α = π/3 = 60°