reason the asynchronous machines are widely used, consists in the simplicity of their design, reliability and manufacturability.The applicability of three-phase and single-phase network, a wide range of power, ease of changing the direction of rotation - all of this makes them indispensable as drives a wide variety of devices, including machine and conveying system.
significant advantage enjoyed by asynchronous machines is their high efficiency.
most common motors - kilowatt, their application is very wide, almost every industrial enterprise, they make up a large part of the drive units.
its name asynchronous electric machines have received because of their angular velocity depends on the mechanical load on the shaft.The higher the resistance torque, so naturally it rotates slowly.The lag angular velocity of the rotor from the rotational speed of the magnetic field generated by current flowing through the stator winding is called slip.It is calculated, as a rule, as a relative value:
S = (ωn-ωp) / ωn
Where:
ωn - the speed of rotation of the magnetic field, vol. / Min .;
ωp - rotor speed, vol. / Min.
Relative magnitude of the load on the sliding shaft shown in particular in that the idle stroke S is virtually zero.
device asynchronous machine is the same as any other motor or generator.The inner surface of the stator is provided with special grooves, which are laid in the winding (in the case of three-phase supply, a single phase motors - two).The rotor also is simple, its design resembles a squirrel cage, and winding are shorted or slip rings.
In the case of a short-circuited rotor due to inductive interference from currents in the stator windings of the rotor arises EMF according to the right hand rule.Further, all simple: two frames crossed by electric current, they interact with each other, and a torque.
asynchronous machines, the rotor is provided with a slip ring work even easier: power to the rotating coil is supplied directly through the carbon brushes.These rotors are also called phase.
Single-phase asynchronous motors have two windings, and start working for generating the initial torque and the unwinding of the rotor to operating angular velocity.These motors are used where the three-phase network is not available, for example, for driving the rotating parts of household appliances.
addition to asynchronous motors are the opposite purpose machines, generators.Their device is substantially similar.To the credit of the Russian electrical engineering, we can confidently talk about the priorities of our country in the field of electric motors of this type.MO-Dobrovolsky Dolivo yet in 1889 the world's first three-phase power applied and obtained a rotating magnetic field.Modern asynchronous machines do not differ from the first three-phase motors of the great Russian scientist and inventor.
