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Shaded pole induction motor produce revolving field by
Inductor
Capacitor
Resistance
Shading coil
Shading coil
A shaded pole induction motor produces a revolving magnetic field using a short-circuited copper band known as a shading coil wrapped around a portion of each salient pole ┬╖ The correct option is D because the shading coil delays the magnetic flux in the shaded portion, creating a rotating magnetic field.
A shaded pole induction motor produces a revolving magnetic field using a short-circuited copper band known as a shading coil wrapped around a portion of each salient pole ┬╖ The correct option is D because the shading coil delays the magnetic flux in the shaded portion, creating a rotating magnetic field.
NsтАЛ=P120fтАЛ тАФ Synchronous speed of the rotating magnetic field
╬жtotalтАЛ=╬жunshadedтАЛ+╬жshadedтАЛ тАФ Total pole flux split with phase displacement
When the main winding is energized, an alternating flux is produced in the pole core ┬╖ This changing flux induces an electromotive force and resultant eddy current in the short-circuited shading coil ┬╖ According to Lenz's law, the induced current opposes the main flux in the shaded portion, shifting the center of the total flux from the unshaded part to the shaded part across the pole face, creating a shifting (revolving) magnetic field from the unshaded to the shaded region.
Direction of rotation is strictly from the unshaded pole to the shaded pole.
Direction of rotation cannot be reversed by reversing supply terminals; it requires physical flipping of the stator.
Starting torque is very low (around 25% to 50% of full load torque).
Efficiency is extremely low (around 5% to 35%) due to continuous I2R copper losses in the shading ring.
Extremely simple construction and robust design
Low cost and low maintenance due to absence of centrifugal switch or capacitors
Very low starting torque
Poor efficiency and low power factor
Small cooling fans and blowers
Electric clocks, record players, and small appliances
Option A (Inductor) is incorrect as an external inductor is not used for split-phase starting in this motor.
Option B (Capacitor) refers to Capacitor-start or Capacitor-run single-phase induction motors.
Option C (Resistance) refers to Resistance split-phase induction motors using a high-resistance auxiliary winding.
D is correct тАФ Shaded pole induction motors utilize a short-circuited copper ring called a shading coil on a portion of the salient pole face to produce a phase-displaced magnetic field, resulting in a revolving field.
Always remember for competitive exams: The rotation of a shaded-pole motor is ALWAYS from the unshaded part to the shaded part of the pole, and it cannot be electrically reversed.