Asynchronous rotation


What is the asynchronous rotation?

Let's place in the rotating magnetic field the metal frame on axes so that the spin axis of the frame was combined with the field spin axis. The field will cross the frame and to induce in it the EMF of subjects big, than the bystyory field crosses the frame as, according to the law of elektromagyonitny induction, е = - Blv.

Схема рамки во вращающемся магнитном поле

The scheme of the frame in the rotating magnetic field.

The EDE direction, induktiyoruyemy in two parties of the frame, it is possible to determine by the right-hand rule.

Only it is necessary to consider that the movement of magnetic field in relation to the conductor is equivalent to the movement of the provodniyok to the opposite side. Therefore, defining the naprayovleniye of EDE, it is necessary to put the palm towards to magnetic lines, and to direct the set aside thumb against the movement of magnetic field, then the extended four fingers will specify the direction of induktiroyovanny EMF. The induced EMFs in two parties of the frame are directed in relation to the round which is formed by the frame, i.e. they develop.

The frame represents the closed round therefore the EMFs induced in it cause some induced current of L. Impact of the rotating magnetic field on this current creates two forces of f=Bil applied to two parties of the frame.

Схема получения вращающегося магнитного поля

The scheme of obtaining the rotating magnetic field.

The direction of these forces can be determined by the left-hand rule. They form the couple and create the torque influencing the frame. Under the influence of this moment the frame has to rotate in the field rotation sense.

However what the frame will quicker rotate, that will otnositelyyono cross more slowly its sides of the line magnetic вра­щающегося fields, i.e. the speed of v of the movement of the field in relation to the frame will decrease. Thereof  the current intensity of i induced in the frame will go down. In turn it causes weakening of the torque influencing the frame. If the frame catches up with the rotary field, then the EMF and current in it will disappear as the parties of the frame will not be пересекать­ся with the rotating magnetic field. Then the rotating moyoment influencing the frame will become equal to zero.

For these reasons the frame rotates more slowly than the field with the asinyokhronny speed (from the Greek word "asinkhronos" — neodyonovremenny), i.e. the frame does the turn not along with oboyoroty weeding. Rotational speed of the frame of ti2 of revolutions per minute is established automatically such that the rotating moyoment created by the induced current equaled to the tormozyayoshchy moment caused by friction in axes, friction about воз­дух, etc. The more the mechanical forces braking the frame, the more slowly it will rotate and the more there will be the current intensity, induced in it.

At asynchronous rotation the field does n1 of turns in the minuyota, and the mobile part called usually by the rotor, only p2 rpm. Lag of the rotor from the field is characterized by sliding: S= (n1 – n2): n1

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