Induction Motor -Basics Single Phase and Three Phase Induction Motors
All these advantages make induction motor to use in many applications such as industrial, domestic and in many applications. Single phase induction motors are used primarily for domestic and light-industrial applications where three-phase supply is generally not available. Advantages and Applications No centrifugal switch is needed. This is the main reason for using a capacitor in single phase induction motors.
These rotor bars are permanently shorted at both ends with the help of end rings as shown in figure. The rotor flux will be lagging in respect of the stator flux. Capacitor-start motors are good general purpose motors and they are ideal for most occasions. The construction of induction motor is very simple and hence maintenance is also easy, resulting in low maintenance cost. Split Phase Induction Motor In addition to the main winding or running winding, the stator of single phase induction motor carries another winding called auxiliary winding or starting winding.
Thus, both running and auxiliary windings remain during running condition, thereby improved power factor and efficiency of the motor. The smaller portion carries the copper band and is called as shaded portion of the pole. The low value capacitor produces more leading phase shift bur less total starting current as shown in phasor diagram. The phasor diagram of two currents in both cases, and the torque-speed characteristics with two windings having different values of capacitors.
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. Now there are two fluxes, one is stator flux, and another is rotor flux. The presentation is successfully added In Your Favorites. The windings are geometrically divided degrees separated. Here the capacitor is capable of running continuously.
This is the simplest arrangement to set up a rotating magnetic field by providing two winding on the same stator core as shown in figure. The single phase motors are simple in construction, cheap in cost, reliable and easy to repair and maintain. Now customize the name of a clipboard to store your clips. The auxiliary or starting winding is made highly resistive whereas the main or running winding is made highly inductive.
Due to this arrangement, bekanntschaft centrifugal switch is not required. Copper coil is known as shading coil. The schematic circuit of this motor is shown in figure below. The most common type of rotor is the squirrel cage rotor. Aluminium bars are moulded on the slots and short-circuited at both ends with a ring.
Split Phase Capacitor Start Run Shaded Pole
The fact that the shaded-pole motor is single-winding no auxiliary winding self-starting one, makes it less costly and results in rugged construction. However, if the rotor of a single phase motor is rotated in one direction by some mechanical means, it will continue to run in the direction of rotation. The soft starter is similar to a primary resistance or primary reactance starter in that it is in series with the supply to the motor. This motor is used in applications, such as compressor, conveyor, machine tool drive, refrigeration and air-conditioning equipment, etc. So in all the above methods or say types of induction motors, the additional flux other than main flux should have a certain phase difference with respect to main or stator flux.
But a comparator gives a logic output indicating the relative potentials on its two inputs. This motor uses entirely different technique to start the motor as compared with other motors so far we have discussed now. The single-phase motor stator has a laminated iron core with two windings arranged perpendicularly.
- The soft starter employs solid state devices to control the current flow and therefore the voltage applied to the motor.
- The flux in shaded pole lags behind the flux in the unshaded pole.
- We have already mentioned above that the single-phase induction motor is not a self-starting motor, and that the three-phase induction motor is self-starting.
The schematic arrangement of this motor is shown in figure below. And some of those are mentioned below. The auxiliary or starting winding carries a series resistance such that its impedance becomes highly resistive in nature. The rotor winding is so arranged that each coil becomes short-circuited. The speed typically varies only by a few percent going from no load to rated load.
Before that, we need to know why a single phase induction motor is not a self-starting motor and how we overcome the problem. Hence there exists a phase difference between these currents and thereby phase difference between the fluxes produced by these currents. What is an Induction Motor?
Ppt on 1-Phase Indu Motor
So, in capacitor start inductor motor and capacitor start capacitor run induction motor we are using two winding, the main winding and the starting winding. By adjusting the position of short circuited brushes on the commutator, the starting torque can be developed in the motor. So, these motors produce very high starting torque. The induction motor always runs at speed less than its synchronous speed. The resultant of these two fluxes produces a rotating flux which rotates in space in one particular direction.
Now there occur large phase angle differences between these two currents which produce an resultant current, I and this will produce a rotating magnetic field. Hence, the starting torque produced by these motors will be considerably lower than that of capacitor start motor. These motors are used in exhaust and intake fans, unit heaters, blowers, etc. These two windings are connected in parallel across the supply. It has a cage rotor and stator.
It combines the advantages of capacitor start type and permanent capacitor type induction motors. The capacitor may be rated only for intermittent duty, the cost of which decreases, as it is used only at the time of starting. The rotor of three-phase induction motors frequently is likewise implied as an anchor.
In an induction motor, the electric current in the rotor needed to produce torque is obtained via electromagnetic induction from the rotating magnetic field of the stator winding. Successfully reported this slideshow. This part where shading coil is placed is generally termed as shaded part of the pole and remaining portion is called as un-shaded part as shown in figure. The rotor comprises of a cylindrical laminated core with axially placed parallel slots for carrying the conductors.
Presentation Description starting methods. Small fans, Toys, Hair Dryers etc Suggestions or difficulties are most welcome at vijayraskar yahoo. Visibility Others can see my Clipboard. The main advantage of these motors is their ability to operate from a single-phase power supply. We connect one capacitor in series with the auxiliary winding.
If the phase difference is more, starting torque will be more. The single phase Induction motors are simple in construction, cheap in cost, reliable and easy to repair and maintain. As the single phase system is more economical and the power requirement in most of the houses, shops, offices are small, which can be easily met by single phase system. The schematic diagram of capacitor start motor is shown in figure below. However, single-phase induction motors does not have self starting torque and are made to rotate using some auxiliaries.
However the power factor is low at rated load and rated speed. These are of different types based on their way of starting since these are of not self starting. This part is of the pole is known as shaded part.
Since the capacitor draws a leading current, the use of a capacitor increases the phase angle between the two currents main and auxiliary and hence the starting torque. It has higher efficiency and pull out torque. Induction motor works on the principle of induction where electro-magnetic field is induced into the rotor when rotating magnetic field of stator cuts the stationary rotor. Also, herne hill singles the power factor of these motors is poor. Speed control of induction motors are difficult.
Types of Single Phase Induction Motor
In the second case, the motor is a balanced two phase one, the two windings having same number of turn. These poles are shaded by copper band or ring which is inductive in nature. In this, the auxiliary winding and capacitor remains in circuit permanently and produce an approximate two phase operation at rated load point.
1phase induction motors
- The flux from the stator cuts the short-circuited coil in the rotor.
- We know that for highly resistive winding the current is almost in phase with the voltage and for highly inductive winding the current lag behind the voltage by large angle.
- This is a modified version of split phase motor.
- This motor is similar to the split phase motor, but in addition a capacitor is connected in series to auxiliary winding.
- The stator of the shaded pole single phase induction motor has salient or projected poles.