Share to Twitter Share to Facebook. A shaded pole motor may be 2 pole or 4 pole. The result is that the flux crowds in the shaded segment of the pole [Fig. According to Lenz law the direction of this current is so as to oppose the cause producing it the decreasing alternating current. The magnetic axis denoted as NE in the picture below.
Coils 2 and 4 remain in series with each other, but arc on open circuit and so are inactive, The main-field flux is shown increasing vertically downward, and the arrows on the shading coils show the current in them. 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. In case of split phase induction motor we use resistance for creating phase difference but here we use capacitor for this purpose.
This sequence keeps on repeating for negative half cycle too. It is then seen that the shading coil must be connected in such a manner as not to have their induced voltages in opposition, or there may not be any current in them, and hence no flux lag. So we can call this part as the shaded part and other part of the pole as unshaded part. Due to fixed of position of shading coils, the direction of rotation of such motors cannot be changed.
Applications of Shaded pole motors induction motor are- Due to their low starting torques and reasonable cost these motors are mostly employed in small instruments, hair dryers, toys, record players, small fans, electric clocks etc. The slot is constructed at some distance apart from the edge of the poles. Overall magnetic axis shifts in nonshaded part as shown in the Fig. This circulates current through shading band as it is short circuited, producing its own flux.
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. Around the smaller of the two areas formed by this slot is placed a heavy copper short-circuited coil, called a shading coil ; the iron around which the shading coil is placed is called the shaded part of the pole, while the free portion of the pole is the unshaded part. Permanent split capacitor PSC motor. 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. Synchronous ac motors are constant-speed electric motors and they operate in synchronism with line frequency. The shaded pole motor may have two or four poles.
WordPress Embed Customize Embed. Let us discuss the constructional details, diagrams and working of shaded pole motors in detail. As soon as this torque starts to revolve the rotor, additional torque is produced by single-phase induction-motor action. According to Lenz law the direction of this current is so as to oppose the cause producing it the decreasing alternating current.
The magnetic axis is denoted as ND in the picture. Search the site Search the site... With starting winding we connect a capacitor so the current flowing in the capacitor i. The production of rotating magnetic field can be explained as below:
The copper rings shade the loops. It is then seen that the shading coil must be connected in such a manner as not to have their induced voltages in opposition, or there may not be any current in them, and hence no flux lag. It has salient poles on the stator excited by single-phase supply and a squirrel cage rotor. The poles are divided into two unequal halves.
So, that the strength of the pole increases. Basic principles of Synchronous Motors. Coils 2 and 4 remain in series with each other, but arc on open circuit and so are inactive, The main-field flux is shown increasing vertically downward, and the arrows on the shading coils show the current in them.
- Basic principles of Shaded Pole Motor. Rotating field of a Shaded Pole Motor. The size and power rating of these motors is very small. Due to their low starting torques they are mostly employed in small instruments, toys, small fans, electric clocks, hair dryers, ventilators, circulators etc.
- When the flux remains almost constant at its maximum value- In this region the rate of rise of current and hence flux remains almost constant. Overall magnetic axis shifts in nonshaded part as shown in the Fig. Capacitor start capacitor run induction motor two value capacitor method. Usually, 2 to 4 poles are used. In this motor two capacitors Cs or starting, and Cr for running, are used. This change of flux induces emf in the shaded coil.
The circulating current develops the flux in the ring which opposes the main core flux of the motor. In order to view it, please contact the author of the presentation. Used in air conditioning and refrigeration equipment and cooling fans. These poles are shaded by copper band or ring which is inductive in nature. Capacitor-start and Capacitor-run Motor.
The shifting of flux is explained below. This copper ring act as a secondary winding for the motor. The direction of this field is from non shaded part of the pole to the shaded part of the pole.
Each pole of the motor is excited by its exciting coil. Hence, using two capacitors, the performance of the motor improves both at the time of starting and then running. A centrifugal switch is connected in series with auxiliary winding. So, these motors produce very high starting torque. Shaded pole motor is a split phase type single phase induction motor.
The circulating current develops the flux in the ring which opposes the main core flux of the motor. This non uniform distribution of flux causes magnetic axis to shift in the middle of the shaded part of the pole. The slot is approximately one third distance from the edge of the pole. So it is quite clear that during the positive half cycle of the alternating current, North Pole shifts from unshaded part to shaded part and during the negative half cycle, the South Pole shifts along from unshaded part to shaded part. Capacitor start inductor motor.