Classification of electric motors: types of units, purpose of asynchronous and synchronous equipment

Electric motors are versatile units capable of converting electricity into mechanical energy. Today there are various types and classifications of electric motors used in domestic and industrial installations. Such a technique may differ in its principle of operation, power supply from direct or alternating current, power and purpose.

Principle of operation and design features

The device of the electric motor is standard, which makes it possible to significantly simplify the operation and repair of equipment. The stator and rotor, which are the main elements of the technology, are located inside the cylindrical groove. When voltage is applied to the stationary stator winding, a magnetic field is excited, which drives the rotor and the shaft of the electric motor.

The constant movement of the rotor is maintained by re-switching the windings or by creating a rotating magnetic field in the stator. If the first method of supporting shaft rotation is characteristic of collector modifications of units, then the formation of a rotating magnetic field is inherent in three-phase asynchronous motors.

The body of the electric motor can be made of aluminum alloy or cast iron. In each case, the choice of body material is based on the scope of the technology and its necessary parameters by weight.

All motors are manufactured with the same installation dimensions, which significantly simplifies their installation and subsequent operation.

Scope of use

The purpose of the electric motor is extremely wide. Such units are used to amplify the power of electrical signals, they are capable of converting direct current into alternating current, and can be used in various types of electrical machines. It is customary to distinguish between units intended for use in industrial equipment, mechanical engineering, on various lifting machines and special equipment. Also very popular are low-power electric motors, which are successfully used in various household tools and kitchen appliances.

Equipment classification

Today, there are various classifications of electric motors, which differ in different criteria and characteristics. Depending on the features of the technique, it is customary to classify it:

1. According to the specifics of the torque, magnetoelectric and hysteresis units are distinguished.
2. By the type of attachment, it is customary to distinguish motors with a horizontal and vertical shaft arrangement.
3. According to the class of protection against environmental influences, a distinction is made between protected, closed and explosion-proof.

In the modification of the hysteresis type, the rotation of the shaft is based on the magnetization reversal of the rotor. Such engines were popular in the past, but today their design is outdated, so they are practically not found. The most widespread are magnetoelectric units capable of operating from alternating or direct current, as well as models of the universal type, which are simultaneously powered by alternating and direct current.

Magnetoelectric installations

The use of magnetoelectric modifications of DC motors provides excellent dynamic and operational characteristics. Depending on its design, such the engine type is divided into two main categories:

• with permanent magnets;
• with electromagnets.

In recent years, modifications with electromagnets, which have more power, are economical in operation and allow you to quickly change the operating parameters equipment.

In collector motors, a brush assembly is used to connect the rotating and stationary parts of the motor. Such units can be performed with independent excitation and the use of permanent magnets, but there are also those that have a self-excited type with mixed, sequential or parallel connection. Collector modifications have mediocre reliability indicators. They require competent and timely service.

Brushless valve assemblies have a closed system that works on the principle of synchronous devices. High-quality brushless motors are equipped with a rotor position sensor, have a coordinate converter, based on the data from which the device operates.

Valve types of motors can be of various sizes and powers. Such units are used in industrial equipment. They are also equipped with rechargeable tools, various toys and mobile phones.

Synchronous electric motors

AC synchronous motors include modifications in which the rotor rotates synchronously with the generated magnetic field. A feature of such units is their high power, which can reach hundreds of kilowatts. The main areas of use for synchronous equipment are high-power industrial plants, wind generators and hydroelectric power plants.

It is customary to distinguish between several modifications of synchronous electric motors:

• stepper;
• reactive;
• with permanent magnets;
• reactive hysteresis;
• valve jet;
• with excitation windings;
• hybrid synchronous.

For stepper synchronous motors with discrete angular movement of the shaft, the position of the rotor will be fixed by applying voltage to the loop windings. The transition to another position of the shaft is carried out by removing power from some windings and then supplying voltage to other windings of the transformer.

Also widely used is a valve reluctance motor, in which the winding is made of semiconductor elements. Valve reaction units are characterized by increased power, while they can be fully controlled by electronics, which allows you to both maintain minimum rpm and quickly reach full power with maximum frequency revolutions. The advantages of synchronous motors are:

• stable rotation speed;
• low sensitivity to voltage drops in the network;
• the ability to use as a power generator;
• minimum power consumption.

However, there are still disadvantages of synchronous devices. These include starting difficulties, maintenance difficulties, and shaft speed adjustment problems. The main purpose of such devices is powerful industrial equipment, where the performance of the units and their reliability are valued.

Asynchronous modifications

For AC induction motors, the rotor speed will differ from the magnetic field. Such units are also called inductive, which is explained by the principle of generating a magnetic field, which occurs due to the movement of the stator. Asynchronous modifications are most prevalent, which is explained by the simplicity of their design, reliability, durability, as well as the possibility of performing both heavy-duty industrial installations and small electric motors intended for use in household instruments.

Depending on the type of electric current with which such units operate, they are usually divided into three categories:

• single-phase;
• biphasic;
• three-phase.

The most widespread today are single-phase asynchronous motors that are capable of operating from a household electrical network. A feature of single-phase motors is the presence of only one working winding and a squirrel-cage rotor on the stator. An alternating single-phase current is supplied to the stator winding, which drives the rotor and motor shaft into rotation. The rotor itself has a cylindrical core with aluminum-cast cells and open ventilation blades. Single-phase squirrel-cage motors are used in small devices such as water pumps and room fans.

Two-phase asynchronous motors are designed for use in a single-phase AC network. Their feature is the presence of two working windings on the stator, located perpendicular to each other. During the operation of the unit, alternating current is directly supplied to one winding, and to the second through the corresponding phase-shifting capacitor. At the output, a rotating magnetic field is formed, which makes it easier to start the electric motor and subsequently maintains a consistently high speed.

Three-phase motors can have squirrel-cage and phase rotor. The units are equipped with three working windings located parallel to each other on the stator. When the motor is turned on in a three-phase network, the magnetic field has a shift in space relative to the winding by 120 degrees. The presence of a short-circuited field makes it easier to start up the device, while subsequently maintaining a stable speed. Modifications of motors with a wound rotor are distinguished by increased power and are used mainly in industrial equipment.

The advantages of asynchronous electric motors are their resistance to voltage surges and versatility of use. Due to the simplicity of the design, their subsequent maintenance is greatly simplified, and the equipment itself is extremely reliable and does not cause any trouble during operation. Depending on their modification, the installations can operate as from a powerful source of electricity in a three-phase network, and from the household electrical network, which allows them to be used in various household appliances and all kinds electrical appliances.

Electric motors are the simplest and extremely reliable devices that are widely used in industry and everyday life. The currently existing types of electric motors allow you to choose a unit that will fully meet the characteristics of its operation. With the help of such motors, powerful machines and equipment, efficient pumps can be driven. Not a single household electrical appliance can do without their use.