Principle of operation of synchronous and asynchronous electric motors

By means of the rotating magnetic field the electric eneryogiya will be transformed to mechanical. For this purpose electric three-phase motors — synchronous and asynchronous serve, from koyotory the last are most widespread.

Асинхронный двигатель в разрезе

The asynchronous engine with the phase rotor in the section: 1 – the bed, 2 – the stator winding, 3 – the rotor, 4 – contact rings, 5 – brushes.

Let's place in the rotating magnetic field the closed round in the form of the rectangular frame (fig. 1a).

At rotation weeding conductors of the frame are crossed by magnetic paths owing to what in them it is directed э. of the village of Napravleyoniye э. by of page it is determined by the right-hand rule and it is noted in the drawing by the cross and the point.

Applying the right-hand rule, it is necessary to consider the relative movement of conductors of the frame against the rotary field. Under the deyyostviye э. of page in the frame is formed current of the same direction. But conductors with current in magnetic field experience action of the elektroyomagnitny forces directed according to the left-hand rule. Concerning the frame axis electromagnetic forces form the moment under the influence of which the frame rotates towards rotation of the field.

Frame speed is always less than the speed of the field n <n0 (the frame "skolyyozit" concerning the field). Thanks to sliding in the frame it is directed э. with, are formed current and electromagnetic forces.

Асинхронный и синхронный двигатели

Figure 1 a) asynchronous engine, b) synchronous motor.

Sliding is estimated by size as a percentage:

S = [(n0 – n): n0] x 100

Rotation of the frame with the speed of the field is impossible as at n = n0 the field does not cross frame conductors, is not directed э. with, are absent current and electromagnetic forces.

The electric motors working by this principle nazyyovat asynchronous.

If instead of the short-circuited frame in magnetic field to place the permanent magnet or the electromagnet with the direct current in its winding, then thanks to interaction of the rotary field with the field of the permanent magnet the torque, also napravyolenny towards rotation of the field is formed (fig. 1).

The permanent magnet in constant magnetic field aims за­нять situation at which the axis of magnet poles in the direction from the South Pole to northern matches the direction of the external field. The permanent magnet "is fond" behind the rotary field, i.e. the field rotates in the same party and with the same speed, as:

n = n0

The electric motors working by such principle nazyyovat synchronous.

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