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What is the phase spread of winding in 3-phase Induction motor?
60
90
120
180
60
The phase spread of a 3-phase AC winding is 60 electrical degrees. This means each phase winding occupies a band of 60 degrees within every pole pair to ensure balanced electromagnetic interaction and optimal winding factor.
The phase spread of a 3-phase AC winding is 60 electrical degrees. This means each phase winding occupies a band of 60 degrees within every pole pair to ensure balanced electromagnetic interaction and optimal winding factor.
PhaseSpread=m180\textdegreeтАЛ тАФ where m is the number of phases (for 3-phase, m=3)
KdтАЛ=msin(╬▓/2)sin(m╬▓/2)тАЛ тАФ Distribution factor where m╬▓=60\textdegree
In a 3-phase machine, the three phases are displaced by 120 electrical degrees in space. To achieve an effective distribution of winding, each phase is distributed over 60 degrees. If the spread were 120 degrees, the phases would overlap significantly, leading to a reduced fundamental EMF due to the cancellation effects of opposing induced voltages.
The phase spread defines the physical zone occupied by one phase winding under a pole.
A 60-degree phase spread is standard for 3-phase AC machines to maximize the distribution factor (KdтАЛ).
Total electrical degrees per pole pair is 360, while per pole is 180.
The winding is distributed to reduce harmonic content and improve the waveform shape.
Improved sinusoidal flux distribution
Better utilization of stator slots
Reduced harmonic EMF components
Increased complexity in winding connections compared to concentrated windings
Slight reduction in total EMF per turn compared to full-pitch concentrated winding
Stator winding design of 3-phase Induction Motors
Synchronous generators and alternators
For a 2-phase machine, the phase spread is 90 degrees.
Option C (120) refers to the phase displacement between phases, not the spread per phase.
Option D (180) is the total electrical space under one pole.
A is correct тАФ The phase spread for a 3-phase induction motor is 60 electrical degrees, which is essential for minimizing harmonics and maximizing the winding factor.
Always distinguish between phase displacement (120┬░) and phase spread (60┬░); confusion between these two is a common trap in MCQ examinations.