The principle of operation and design of a synchronous motor: advantages, design features

The principle of operation of a synchronous motor looks almost the same as that of an asynchronous motor. However, this type of power plant has significant differences and features. And although the share of asynchronous units in industry is 96% of the total number of electric motors, other options, including synchronous ones, also found their consumers.

The main differences

Basically, synchronous and asynchronous motors are not much different from each other. The key difference between the first models is that the rotation of the armature is carried out at the same speed as the rotation of the magnetic flux. At the same time, a wire winding is built inside the installation, transmitting alternating voltage, and not a squirrel-cage rotor, as in asynchronous devices. Also, some designs are equipped with permanent magnets, but they significantly increase the cost of the engine.

As the load increases, the rotor speed remains the same. It is this feature that characterizes this type of power plant. The key requirement for such machines is as follows: the number of poles in a moving magnetic field must correspond to the number of poles of an electromagnet on the rotor.

Synchronous device design

The principle of operation and the structure of synchronous machines remain clear even for inexperienced consumers. The key components of the system include the following nodes:

1. The stator is a stationary part of the installation, on which three windings are located. They are star or delta connected. As a material for the manufacture of the stator, plates made of super-strong electrical steel are used.
2. The rotor is a moving element of the motor, equipped with a winding. During operation of the installation, this winding passes a certain voltage.

There is a small air gap between the fixed and the moving part of the system, which guarantees balanced operation of the motor and unhindered influence of the magnetic field on key components unit. The motor also contains the bearings required for the rotor rotation and a terminal box. The latter is located at the top of the mechanism.

Principle of operation

Studying the principle of operation of a synchronous motor, it is important to understand that, like other types of power plants, they convert one type of energy to another. In simple words, built-in mechanisms make mechanical energy from electrical energy, and all the work takes place according to the following algorithm:

1. An alternating voltage is passed through the winding on the stator, resulting in the formation of a magnetic field.
2. Then a similar voltage is applied to the rotor windings, which also creates a magnetic field. In the presence of permanent magnets in the structure, such a field is present by default.
3. When two magnetic fields collide, they counteract each other, i.e. one pushes the other. It is this principle that causes the movement of the rotor placed on the bearings.

Knowing how a synchronous motor works and works, it remains to correctly distribute its energy and use it for the required purposes. However, the performance and efficiency of the system will be maximized only if it can be brought to normal operation.

Generator arrangement

There is a reverse version of synchronous motors - synchronous generators. They work a little differently:

1. The stationary stator winding does not transmit voltage. On the contrary, it is removed from her.
2. An alternating voltage is supplied through the rotor winding, while the consumption of electrical energy is very small.
3. The movement of the generator is driven by a diesel or gasoline engine. It can also be spinned by the power of water or wind.
4. EMF induction occurs in the stator winding, and a potential difference appears at the ends. This is due to the moving magnetic field around the rotor.

But in any case, it is necessary to stabilize the voltage at the generator output. This is done by connecting the rotor winding to a voltage source.

Depending on the design features, the rotor can be equipped with permanent or electric magnets or so-called poles. As for inductors, in synchronous installations they are:

1. Explicit pole.
2. Implicit polarity.

These types differ from each other only in the relative position of the poles. To reduce the resistance of the magnetic field and improve the penetration of current, the mechanism is equipped with cores, which are made of ferromagnets. The cores are located both in the rotor and in the stator, and exclusively electrical steel is used for their manufacture. The fact is that this material contains a large amount of silicon, which significantly reduces eddy currents and improves the electrical resistance of the core.

Launching the installation

When using synchronous motors, there are a lot of difficulties at the stage of their start-up. Because of this, they are not very popular and are inferior to asynchronous options.

From the moment they appeared on the market, the operation of synchronous units was provided by a special asynchronous device, which was mechanically connected to the rest of the units. In fact, the rotor was accelerated to the desired frequency using the second type of motors. Modern asynchronous devices do not need to connect additional mechanisms, and all that is required for their operation is the appropriate voltage for the stator winding.

As soon as the system reaches the desired speed, the booster motor will be shut off. In this case, the magnetic fields from the electric motor will bring it to work in a synchronous mode. To overclock the unit, you will have to use another motor with a power of 10% of the power of the synchronous motor. When accelerating an electric motor by 1 kW, a 100 W accelerating system is used. According to experts, such indicators are quite enough for a balanced operation of the machine in idle mode or with light load.

Applications

The synchronous electric motor is an important invention for various industries. But due to its complex design and high cost of equipment, it is rarely used.

The fields of application of electric motors of the synchronous type are very limited. In most cases, the installation is used to increase the power indicators in the power system, which due to their ability to function at any power factor and excellent cost-effectiveness.

The devices are in demand for those conditions where the rotation speed barely reaches 500 rpm and there is a need to increase the power. Currently, they are being actively implemented in piston pumps, compressor plants, rolling mills and other systems.