how single phase induction motor works ?

Answer 1

there are two sep windings and a capacitance is connected to aux. winding this creats a phase diff, making it as two phase motor...
thus an alternating flux causes the rotor to rotate

Answer 2

Single-phase AC induction motors

Three-phase motors inherently produce a rotating magnetic field. However, when only single-phase power is available, the rotating magnetic field must be produced using other means. Several methods are commonly used.

A common single-phase motor is the shaded-pole motor, which is used in devices requiring low torque, such as electric fans or other small household appliances. In this motor, small single-turn copper "shading coils" create the moving magnetic field. Part of each pole is encircled by a copper coil or strap; the induced current in the strap opposes the change of flux through the coil (Lenz's Law), so that the maximum field intensity moves across the pole face on each cycle, thus producing the required rotating magnetic field.

Another common single-phase AC motor is the split-phase induction motor, commonly used in major appliances such as washing machines and clothes dryers. Compared to the shaded pole motor, these motors can generally provide much greater starting torque by using a special startup winding in conjunction with a centrifugal switch.

In the split-phase motor, the startup winding is designed with a higher resistance than the running winding. This creates an LR circuit which slightly shifts the phase of the current in the startup winding. When the motor is starting, the startup winding is connected to the power source via a set of spring-loaded contacts pressed upon by the not-yet-rotating centrifugal switch. The starting winding is wound with fewer turns of smaller wire than the main winding, so it has a lower inductance (L) and higher resistance (R). The lower L/R ratio creates a small phase shift, not more than about 30 degrees, between the flux due to the main winding and the flux of the starting winding. The starting direction of rotation may be reversed simply by exchanging the connections of the startup winding relative to the running winding.

The phase of the magnetic field in this startup winding is shifted from the phase of the mains power, allowing the creation of a moving magnetic field which starts the motor. Once the motor reaches near design operating speed, the centrifugal switch activates, opening the contacts and disconnecting the startup winding from the power source. The motor then operates solely on the running winding. The starting winding must be disconnected since it would increase the losses in the motor.

In a capacitor start motor, a starting capacitor is inserted in series with the startup winding, creating an LC circuit which is capable of a much greater phase shift (and so, a much greater starting torque). The capacitor naturally adds expense to such motors.

Another variation is the Permanent Split-Capacitor (PSC) motor (also known as a capacitor start and run motor). This motor operates similarly to the capacitor-start motor described above, but there is no centrifugal starting switch and the second winding is permanently connected to the power source. PSC motors are frequently used in air handlers, fans, and blowers and other cases where a variable speed is desired. By changing taps on the running winding but keeping the load constant, the motor can be made to run at different speeds. Also provided all 6 winding connections are available separately, a 3 phase motor can be converted to a capacitor start and run motor by commoning two of the windings and connecting the third via a capacitor to act as a start winding.

Repulsion motors are wound-rotor single-phase AC motors that are similar to universal motors. In a repulsion motor, the armature brushes are shorted together rather than connected in series with the field. Several types of repulsion motors have been manufactured, but the repulsion-start induction-run (RS-IR) motor has been used most frequently. The RS-IR motor has a centrifugal switch that shorts all segments of the commutator so that the motor operates as an induction motor once it has been accelerated to full speed. RS-IR motors have been used to provide high starting torque per ampere under conditions of cold operating temperatures and poor source voltage regulation. Few repulsion motors of any type are sold as of 2006.

Answer 3

Because the motor is single phase the rotating magnetic field has to be created as an extra part of the motor. This is done with capacitors, or extra windings in the motor that cause a separate field with a phase shift.

Answer 4

No, not true. first of all, very few types of motors will operate as generators. Second, to feed power back into the grid, you need several conditions: 1. Permission of the power company 2. A new power meter that runs backwards 3. Special electronics to control the frequency, phase and voltage of the power, approved by the power company Even if the motor operates as a generator, it will not generate the correct frequency and phase. .

Answer 5

If this is what I think it is, it's a motor with three points of an electric field around it. These fields are stimulated (a current run through it) in turn, creating a rotating magnetic field, which "pulls" the rotor, causing it to spin. The rotor shaft, naturally, is then attached to gears or an object which we want to spin.

Answer 6

Its working can be explained by double field revolving theory. It has a pulsating ac waveform produced by distributed stator windings and this waveform can be shown to consist of two equal magnitude rotating magnetic fields in opposite direction.Thes e fields on cutting rotor bars lead to emf in them,which being short circuited lead to currents in them and subsequently rotor mmf is produced which rotates with stator mmf at same speed and direction. Interaction of these two mmf produces torque ,being equal to forward field torque subtracted from backward field torque, and as a result it rotates in any one direction(forward field direction) at any speed other than zero. At starting,since both torques ,created by forward and backward field) are equal, a special auxiliary winding is required along with main winding in stator to produce a finite torque in any one direction. This stator auxiliary winding must have some spatial and time phase difference with the main field winding axis,so as to produce some torque angle. This starting torque is maximized when capacitors are used.

https://www.electrikals.com/products/rm-motors/havells?mid=28&cid=641&page=1&pagesize=20

Answer 7

There is an excellent explanation in Wikipedia.com.

Answer 8

try this howstuffworks.com