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In single-phase induction motor ┬╖ How are the poles and pitches in the concentric windings?
single pole, single pitch
single pole, different pitches
different pole, single pitch
different pole, different pitches
single pole, different pitches
In single-phase induction motors employing concentric windings, each pole group is formed by coils of varying sizes nested within each other ┬╖ Consequently, all coils belong to the same pole, but they span different pitches (different number of slots per coil).
In single-phase induction motors employing concentric windings, each pole group is formed by coils of varying sizes nested within each other ┬╖ Consequently, all coils belong to the same pole, but they span different pitches (different number of slots per coil).
NpтАЛ=PolesSlotsтАЛ тАФ definition of pole pitch in slots
KdтАЛ=msin(╬▓/2)sin(m╬▓/2)тАЛ тАФ distribution factor representing winding effect
Concentric windings are designed to distribute the conductors across the pole pitch to improve the EMF waveform and reduce harmonics ┬╖ Because the inner coils span fewer slots than the outer coils in a single-pole grouping, the magnetic flux distribution is effectively shaped by these different pitches while maintaining a single magnetic pole polarity.
Concentric windings use coils of different sizes (pitches) to form a single pole.
This arrangement reduces the total number of coil groups compared to lap windings.
Commonly used in fractional horsepower single-phase motors.
The winding is not uniform; coil spans are varied to optimize flux distribution.
Simpler end-turn formation
Reduced copper usage for connections
Easier to insert into stator slots
Unequal coil lengths lead to unequal resistance and inductance
Not suitable for high-speed or large-capacity machines due to leakage flux issues
Ceiling fans
Small domestic appliances
Fractional horsepower induction motors
Concentric windings are often called 'chain windings' due to the interlocking nature of the coils.
Option A is incorrect because coils of the same pole must have varying spans to be defined as concentric.
Options C and D refer to configurations not found in standard concentric single-phase designs.
B is correct тАФ concentric windings feature coils of different pitches grouped under a single magnetic pole.
Always remember that in concentric windings, the 'pitch' refers to the slot span of individual coils, which necessarily varies when they are nested under a single pole.