The power losses are very high in the shaded pole induction motor. Popular Tags Blog Archives. Share to Twitter Share to Facebook.
Thus, the chances of failure of the motor are less. The torque speed characteristics is shown in the Fig. Since the copper band is short circuit the current starts flowing in the copper band due to this induced emf. Usually, 2 to 4 poles are used.
Shaded-Pole SIngle-Phase Motors
The copper rings shade the loops. The flux induces in the shaded portion of the motor, i. The flux produced by this induced emf has no effect on the main flux and hence distribution of flux remains uniform and the magnetic axis lies at the center of the pole. Since the torque produced by these motors depends upon the phase angle difference, which is almost 90 o. Some of the important characteristics of shaded pole induction motors are given below.
The shifting of flux is explained below. The poles of shaded pole induction motor consist of slots, which are cut across the laminations. August 24, 2018 February 24, 2012 by Electrical4U. The details of characteristics of shaded pole motor will be discussed later. It finds applications in fans and blowers in heaters and air conditioners.
The alternating current, after reaching the peak starts to decrease rapidly and in turn decreases the main flux. The smaller part of the slotted pole is short-circuited with the help of a coil. The shifting of flux is explained below. Considering a cycle of alternating current fig 1 applied to the stator winding we will explain the working of shaded pole motor.
This shifting flux is like a rotating weak field moving in the direction from unshaded portion to the shaded portion of the pole. The circulating current develops the flux in the ring which opposes the main flux of the motor. The short circuited copper coil described above is placed in this slot. Since the change is current is so small, the induced current at shading ring is also small and negligible.
Construction is simple and robust because there is no centrifugal switch. So the shading ring does not affect the distribution of main flux. Consequently this produces an effect of rotating magnetic field, the direction of which is from nonshaded part of the pole to the shaded part of the pole. Because of the following reasons the motor has poor efficiency.
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The current carried by the stator winding is alternating and produces alternating flux. The lamination means multiple layers of material are used for making the poles. A centrifugal switch is connected in series with auxiliary winding.
The currents in the two main and auxiliary stator windings also must be at an angle of , to produce maximum starting torque, as shown in a balanced two-phase stator. This shifting of magnetic axis continues for negative cycle also and leads to the production of rotating magnetic field. So the rotor starts rotating in the direction of the shift from unshaded part to shaded part. We already know that single phase induction motor is not self starting because the magnetic field produced is not rotating type. Current Transformer CT - Construction and Working Principle The large alternating currents which can not be sensed or passed through normal ammeter, and….
According to lenz's law, the direction of this current is so as to oppose the cause i. Performance Characteristics of Universal Motors. Definition Shaded pole motor is a salient-pole, split phase type, squirrel cage rotor single phase induction motor provided with one or more auxiliary short-circuited stator winding is placed in magnetic position from the main winding. As the flux decreases portion BC of the alternating current cycle , current is induced in the shading coil so as to oppose the decrease in current. The starting winding is highly resistive so, the current flowing in the starting winding lags behind the applied voltage by very small angle and the running winding is highly inductive in nature so, the current flowing in running winding lags behind applied voltage by large angle. The phasor diagram of two currents in both cases, and the torque-speed characteristics with two windings having different values of capacitors.
The salient pole means the poles of the magnet are projected towards the armature of the motor. Automatically changes to Flash or non-Flash embed. The direction of current in shading coil is such as to oppose the cause producing it from Lenz law. It is also known that, in a balanced two-phase IM having two winding, each having equal number of turns and placed at a space angle of 90 electrical , and are fed from a balanced two-phase supply, with two voltages equal in magnitude, at an angle of , the rotating magnetic fields are produced, as in a three-phase IM.