Synchronous and asynchronous motor: differences, operating principle, application

The classification of engines is based on different parameters. According to one of them, a synchronous and asynchronous motor is distinguished. The differences in instruments, the general characteristics and the principle of operation are described in the article.

Synchronous motor

This type of engine is able to work simultaneously as a generator, and as, 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 motors are widely used in many areas, for example, for electrical wires that need constant speed.

Principle of synchronous motor operation

The basis of its functioning is the interaction 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 poles, and for weak ones - permanent magnets.

The principle of operation of a synchronous motor includes (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.

Advantages and disadvantages

The main disadvantages of this type of engine are:

• The need for DC winding;
• Complexity of launching;
• Sliding contact.

Most generators, wherever they are used, are synchronous. Advantages of such engines as a whole are:

• The highest reliability;
• The highest coefficient of efficiency ;
• Ease of maintenance.

Asynchronous motor

This type of device represents a mechanism aimed at transforming the electrical energy of an alternating current into a mechanical one. 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 type of which the squirrel-cage induction motors can be with a phase rotor.

Operating principle

The engine is operated on the basis of the interaction of the magnetic stator field and the currents induced in 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 widespread use of one type and the limited one - the other?

Synchronous and asynchronous motor: differences

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 also attracts a magnetic rotor. Their speed is the same. Hence the name - synchronous.

It can be achieved, in contrast to the asynchronous, even the voltage advance over the phases. Then the device, like condenser batteries, can be used to increase power.

Asynchronous motors, in turn, are simple and reliable, but their disadvantage is the difficulty in adjusting the rotational speed. To reverse the three-phase asynchronous motor (i.e., changing the direction of its 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 frequency of rotation, then there are also a synchronous and asynchronous engine of difference. In the synchronous type, this indicator is constant, in contrast to the asynchronous type. Therefore, the former is used wherever constant speed and complete controllability is required, for example in pumps, fans and compressors.

Identify on this or that device the presence of the types of devices under consideration is very simple. The asynchronous motor will not have a round number of revolutions (for example, nine hundred and thirty per minute), while on the synchronous one it will be round (for example, thousand revolutions per minute).

Both those and other motors are quite difficult to control. The synchronous type has a rigid characteristic of mechanics: at 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.