Here in this article, we use the two-pole motor for the sake of simplicity. The speed of the motor is inversely proportional to the number of poles used in the motor. Stator — The stator of the shaded pole motor has a salient pole. The salient pole means the poles of the magnet are projected towards the armature of the motor. Each pole of the motor is excited by its exciting coil.
The copper rings shade the loops. The loops are known as the shading coil. The poles of the motor are laminated. Lamination means multiple layers of material are used for making the poles. So, that the strength of the pole increases. In such a way that their operating characters meet demands. Single-phase AC motors are cheaper in cost, more reliable, simple in construction, and very easy to repair.
These are widely used in fans, cleaners, refrigerators, blowers, washing machines, etc. Single-phase AC motors are divided into three types. They are single-phase induction motor, commutator type single phase motor, single-phase synchronous motor. Single-phase induction motors are further divided into four types- split-phase motor, shaded pole induction motor, reluctance start induction motor, and repulsion starts induction motor.
This article describes a shaded pole motor and its working. Definition: A shaded pole induction motor is a simple single-phase induction motor , which is self-starting with one of the poles shaded by the copper ring. The other name of the copper ring is a shaded ring, where it acts as a secondary winding motor. It rotates only in one direction particularly and reverses moment is impossible.
This motor has very high power induction losses and also has a very low power factor. Starting torque induced in the motor is very low. Due to these reasons, it has poor efficiency. Shaded pole induction motor is nothing but a self-starting single phase motor whose main pole is shaded by the auxiliary winding or an external winding. This external winding is called a shaded coil or shaded band. Stator, the stationary part which carries the main winding and shaded winding of the motor.
The stator poles are projected i. Mostly it will be designed with two or four poles as per the speed requirements. Designing a higher number of the pole, increase the complexity of the motor. It called a shade band or shaded coil. Both ends of the copper band will be shorted to form a closed circuit.
It acts as a transformer secondary winding. The individual pole has own shade band as shown in figure 1. The construction of the rotor is the same as the normal single-phase induction motor. The rotor is skewed by 60 deg to reduce the magnetic locking. In order to increase the starting torque of the motor, the rotor is designed with V type skewing. V-skewing is costlier, but they have a better way to reduce the magnetic locking between the rotor and starter. The working principle of shaded pole induction motor is simple, the main winding carries alternating current and produces magnetic flux in the stator coil.
Considering a cycle of alternating current fig 1 applied to the stator winding we will explain the working of shaded pole motor. During the portion OA of the alternating-current cycle [Fig 1], the flux begins to increase and an e. During the portion AB of the alternating-current cycle, the flux has reached the almost maximum value and is not changing.
Consequently, the flux distribution across the pole is uniform [See Fig 3] since no current is flowing in the shading coil. As the flux decreases portion BC of the alternating current cycle , the current is induced in the shading coil so as to oppose the decrease in current. Thus the flux in the shaded portion of the pole is strengthened while that in the unshaded portion is weakened as shown in Fig 4. Some of the important characteristics of shaded pole induction motors are given below.
The details of the characteristics of the shaded pole motor will be discussed later. The salient features of this motor are extremely simple construction and absence of centrifugal switch.
Since starting torque, efficiency and power factor are very low, these motors are only suitable for low power applications e. Related Articles.
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