How does a shaded-pole motor start and rotate in a specific direction?
1 Answer
A shaded-pole motor is a type of single-phase induction motor that is simple in design and is commonly used in small appliances like fans, pumps, and other low-power applications. It gets its name from the shading coils or copper loops, also known as shading rings or shading bands, that are embedded on one side of the motor's pole faces.
Here's how a shaded-pole motor starts and rotates in a specific direction:
Construction: The shaded-pole motor consists of a stator (stationary part) and a rotor (rotating part). The stator has a laminated iron core with multiple poles and winding. One side of each pole face has a shading coil or loop made of copper or aluminum.
AC Power Supply: When AC voltage is applied to the motor's main winding, it produces an alternating magnetic field. However, due to the presence of shading coils, the magnetic field on one side of each pole face lags behind the other side in terms of phase.
Starting: As the AC voltage is applied, the shaded poles create an asymmetry in the magnetic field. This asymmetry results in a small phase shift between the magnetic fields on the shaded and unshaded sides of each pole. This phase shift generates a starting torque, causing the rotor to begin rotating.
Rotation: The rotor starts to rotate in the direction determined by the phase difference between the shaded and unshaded poles. The rotation continues as long as the AC voltage is applied.
Direction Control: The direction of rotation is typically determined during the manufacturing process by the placement of the shading coils. The design of the shading coils and their placement influences the phase shift and, consequently, the direction of rotation. However, unlike some other types of motors, shaded-pole motors have limited control over reversing their direction. They are usually designed to rotate in one direction only.
It's important to note that shaded-pole motors are relatively low-power and have low efficiency compared to other types of motors like capacitor-start induction motors. They are primarily used in applications where precise control over direction is not critical and cost-effectiveness is a primary concern.
Here's how a shaded-pole motor starts and rotates in a specific direction:
Construction: The shaded-pole motor consists of a stator (stationary part) and a rotor (rotating part). The stator has a laminated iron core with multiple poles and winding. One side of each pole face has a shading coil or loop made of copper or aluminum.
AC Power Supply: When AC voltage is applied to the motor's main winding, it produces an alternating magnetic field. However, due to the presence of shading coils, the magnetic field on one side of each pole face lags behind the other side in terms of phase.
Starting: As the AC voltage is applied, the shaded poles create an asymmetry in the magnetic field. This asymmetry results in a small phase shift between the magnetic fields on the shaded and unshaded sides of each pole. This phase shift generates a starting torque, causing the rotor to begin rotating.
Rotation: The rotor starts to rotate in the direction determined by the phase difference between the shaded and unshaded poles. The rotation continues as long as the AC voltage is applied.
Direction Control: The direction of rotation is typically determined during the manufacturing process by the placement of the shading coils. The design of the shading coils and their placement influences the phase shift and, consequently, the direction of rotation. However, unlike some other types of motors, shaded-pole motors have limited control over reversing their direction. They are usually designed to rotate in one direction only.
It's important to note that shaded-pole motors are relatively low-power and have low efficiency compared to other types of motors like capacitor-start induction motors. They are primarily used in applications where precise control over direction is not critical and cost-effectiveness is a primary concern.