what do you mean by slip in 3 phase induction motor?

Question

these question related to electrical oriented.

Answer 1

% differnce beetween the rpm of stator and rpm of rotor.must be less than one in practical applications.

Answer 2

A force is produced when an electric current pass through a magnetic field. This is the principle that electric motors run on. Induction motors are quite ingenious inventions in that they use one source of power (current) to create the magnetic field and the current to pass through it.

When you excite the stator of an induction motor it creates a magnetic field that is rotating with in the motor at a frequency that is related to the excitation frequency and the physical design of the motor. This rotating field induces a current in the rotor very similar to a transformer. This induced current is now flowing within the field that created it. The tricky part is that if it was flowing at the exact same frequency as what excited it then there would not be any force created as the stators field and the rotor's current would be in phase. What happens is the rotor turns at a frequency some what lower than the excitation frequency. This difference is what causes a phase difference between the magnetic field and the flowing current that creates the force that makes the motor turn. This difference is speed is called slip. If the load on the motor is low then the motor runs closer to synchronous speed. As the load increases, the slip increases and the force increases to drive the load.

Answer 3

From wikpedia:

The speed of the AC motor is determined primarily by the frequency of the AC supply and the number of poles in the stator winding, according to the relation:

Ns = 120F / p

where

Ns = Synchronous speed, in revolutions per minute
F = AC power frequency
p = Number of poles per phase winding

Actual RPM for an induction motor will be less than this calculated synchronous speed by an amount known as slip that increases with the torque produced. With no load the speed will be very close to synchronous. When loaded, standard motors have between 2-3% slip, special motors may have up to 7% slip, and a class of motors known as torque motors are rated to operate at 100% slip (0 RPM/full stall).

The slip of the AC motor is calculated by:

S = (Ns − Nr) / Ns

where

Nr = Rotational speed, in revolutions per minute.
S = Normalised Slip, 0 to 1.

Answer 4

If you operate the motor unloaded, the rotor will spin at the same frequency as the electrical induction field is rotating (synchronously). Under load, the rotor can't quite keep up and "slips" which is how the motor develops its torque to drive the load. If the motor is operated with a locked rotor (on a test stand?) it will develop maximum torque at maximum slip. Of course that is what helps the motor start moving its load from a dead stop.

Answer 5

Slip Speed of the Induction Motor is defined as the difference between the synchronous speed and the actual rotor speed. An induction motor cannot run at synchronous speed. Let us consider that the rotor of the induction motor is running at the synchronous speed. At this condition, the rotor conductors do not cut the flux and as a result, there is no generation of voltage, current and hence, no torque.

Answer 6

The slip ring induction automobiles generally have a “section-Wound” rotor. this manner of rotor is presented with a three-section, double-layer, disbursed winding which includes coils utilized in alternators. The rotor center is created from metallic laminations that have slots to deal with formed 3-single section windings. those windings are located a hundred and twenty tiers electrically aside. The rotor is wound for as many poles because of the fact the variety interior the stator and is often 3-section, even nonetheless the stator is wound for 2-section. those 3 windings are “starred” internally and the different end of those 3 windings are further out and linked to 3 insulated slip-rings fastened on the rotor shaft itself. the three terminal ends touch those 3 slip rings by ability of carbon brushes that are held against the rings by ability of a spring assembly.