shaded pole induction motor is the type of single phase induction motor . Since it is self started motor, so it is also known as self starting single phase induction motor.
in this type, single phase induction motor or shaded pole motor one pole is shaded by the copper ring. The copper ring is also known as shading ring. Where copper ring act as secondary coil or secondary winding. The shaded pole induction motor rotates only in one direction . Reverse action in shaded pole induction motor is not possible. Read more for detail explanation.
Construction of shaded pole induction motor
the shaded pole induction motor can be designed of two or four poles. The speed of the motor is inversely proportional to the number of poles that are used in the motor. It means that if the number of poles are more then a speed of motor will be less and if the number of poles are less in the motor, then the speed of motor will be high .
Stator
salient, pole stator is used in shaded pole induction motor meaning of salient is magnets are projected towards the armature of the motor and each pole of the motor is excited by the exciting coil .
The copper ring makes a loop or we can say it look like loop that is known as shading coil
stator of shaded pole induction motor has laminated pole. Meaning of lamination is various thin strip attached together to make stator.
lamination increases the strength of the stator as well as it reduces the eddy current loss and Stator slots are constructed at some distance, apart from the edge of the poles
Rotor
a squirrel cage rotor is used in the shaded pole induction motor. In a squirrel cage rotor bars are skewed at an angle of 60°. We constructed a skewed bar for the greater torque.
The construction of the motor is very simple, or we can say it is easy to construct because it has not any type of commutator , carbon brush, collector, ring, etc.
the shaded pole induction motor, don’t uses any centrifugal switches that’s why the chances of failure of the motor are less .
centrifugal, which is the type of electrical device that starts operating by the help of centrifugal force and centrifugal force generated by the rotating shaft, and it is also used for the controlling the speed of the soft
working of shaded pole induction motor
first of all we give single phase AC supply to the stator winding where main winding is placed so due to AC current in main widening alternating magnetic flux produces. We consider as a main flux and when main flux cut the copper ring at shaded portion of the stator pole then EMF induced in the copper ring according to the faradays law of the electromagnetic induction. According to this principal, whenever. Changing magnetic flux cuts the stationary conductor ,Then EMF induce in the conductor. That’s why here EMF is inducing in the copper ring. And current circulated because copper ring remain short circuit. Here it is rounded, so it is completing the circuit . So due to current in the copper ring another magnetic flux produces around the copper ring that we consider as shaded flux . Now we have two fluxes main flux, and shaded flux. Suppose main magnetic flux is the (Øm) and shaded flux is the (Øs) , shaded flux (Øs) will oppose the main flux (Øm) from Lenz law .
When both magnetic flux opposes to each other then both magnetic field displaced by some angle that will less than 90° but due to phase displacement rotating magnetic field produces in the gap of stator and rotor . So due to that rotating magnetic field torque acts on the rotor in tangential direction and rotor starts to rotate in the direction of shaded portion .
here, pole of motor play very important role because pole of the motor is inversely proportional to the speed of the motor . If number of pole is less then speed of motor will high and it’s vice versa .
Application of shaded pole induction motor
- That type of load where requirement of low starting torque shaded pole motor is used
- shaded pole motor is used in table fan
- it is used in exhaust fan
- this type of motor is used in hair dryer
- this type of single phase induction motor is used in fans, refrigeration, and air conditioning equipments.
Advantages
- shaded pole motor has simple construction. It has not requirement of capacitor or centrifugal switch.
- it has long life
- it take very less current in a starting, and it does not cause of voltage drop in nearest feeder
- it has not requirement of proper maintenance.
- it is self started motor not requirement of external device .
Disadvantages
- this type of motor is not suitable for high starting torque
- it cannot rotate in reverse direction
- it provides poor power factor in a ppstarting
why this type of motor is designed for low power rating
the power loss are very high in the shaded pole induction motor and the power factor of the motor is very low, as well as the starting torque induces in the induction motor due to this reason, shaded pole motor has poor efficiency. That’s why we design low power rating of shaded pole motor .
why reverse action of rotor is not possible in shaded pole induction motor ?
shaded pole induction motor rotates only in one direction due to effect of the shading ring or we can say shading coil . the main winding placed on stator pole and copper ring act as secondary winding , main winding produces main flux and secondary winding produces shading flux where both flux opposes to each other as a result rotating magnetic flux produces and rotor rotates as the same direction of rotating magnetic field . When we study three phase in induction motor working principle, then we will clearly understand about the rotating magnetic field or RMF. And also, we will discuss production of rotating magnetic field theory.
Physical characteristics of shaded pole induction motor
- it’s construction is very simple
- in this type motor power factor efficiency, and a starting torque is low
- if we have requirement of reversing the direction, then this facilities is not available in this type, single phase induction motor
- these type of induction motors are very cheap at low price. You can purchase from market.
- this type of motor is designed at low power (40 w or less ) rating and a small size
Shaded pole motor – Video