The classification of engines is based on different parameters. According to one of them, a synchronous and asynchronous engine is distinguished. The differences in instruments, the general characteristics and the principle of operation are described in the article.
This type of engine is able to work simultaneouslyand as a generator, and how, in fact, the engine. Its device is akin to a synchronous generator. A characteristic feature of the engine is the unchangeable frequency of rotary rotation from the load.
These types of engines are widely used in many areas, for example, for electrical wires that need constant speed.
The basis of its functioning is laid downinteraction of the rotating magnetic field of the armature and the magnetic fields of the inductor poles. Usually the armature is located in the stator, and the inductor is located in the rotor. For powerful motors, electric magnets are used for the poles, and for weak ones - permanent magnets.
The principle of synchronous motor operation includesitself (briefly) and an asynchronous mode, which is usually used to accelerate to the necessary (that is, nominal) rotation speed. At this time, the inductor windings are short-circuited or by means of a rheostat. After reaching the required speed, the inductor starts to be supplied with a direct current.
The main disadvantages of this type of engine are:
Most generators, wherever they are used, are synchronous. Advantages of such engines as a whole are:
This type of device represents a mechanism,directed on transformation of electric energy of an alternating current in mechanical. From the very name "asynchronous" we can conclude that this is a non-simultaneous process. Indeed, the rotational frequency of the stator magnetic field is higher than the rotor field always.
Such a device consists of a stator of a cylindrical shape and a rotor, depending on the kind of which asynchronous short-circuited motors can be with a phase rotor.
The engine is operated on the basis ofthe interaction of the magnetic stator field and the currents induced by the same field in the rotor. The turning moment appears when there is a difference in the rotation frequency of the fields.
Let us now summarize how a synchronous engine differs from an asynchronous one. What explains the wide application of one type and the limited one - the other?
The difference between the work of the engines is in the rotor. In a synchronous type, it consists of a permanent or electric magnet. Due to the attraction of opposite poles, the rotating field of the stator attracts a magnetic rotor. Their speed is the same. Hence the name - synchronous.
Asynchronous motors, in turn, are simple andreliable, but their disadvantage is the difficulty in adjusting the rotational speed. To reverse the three-phase asynchronous motor (i.e., changing its direction of rotation in the opposite direction), the arrangement of the two phases or two linear wires approaching the stator winding is changed.
If we consider the rotational frequency, then uhere the synchronous and asynchronous engine differences. In the synchronous type, this indicator is constant, in contrast to the asynchronous type. Therefore, the former is used wherever a constant speed and complete controllability is required, for example in pumps, fans and compressors.
To reveal on this or that device presencethe types of instruments under consideration is very simple. On an asynchronous motor there will be no round number of revolutions (for example, nine hundred and thirty per minute), while on a synchronous motor there will be a round (for example, thousand revolutions per minute).
Both those and other motors are controlled sufficientlycomplicated. The synchronous type has a rigid characteristic of mechanics: for any varying load on the motor shaft, the speed of rotation will be the same. At the same time, the load must, of course, change, taking into account that the engine is able to withstand it, otherwise it will lead to a breakdown of the mechanism.
So the synchronous and asynchronous engine is arranged. Differences of both types determine the scope of their use, when one species copes with the task in an optimal way, for another it will be problematic. At the same time, one can also find combined mechanisms.</ p>