The electric motor is a special converter. It is a machine where electrical energy is converted and converted into mechanical energy. The principle of operation of the engine is based on electromagnetic induction. There are also electrostatic motors. It is possible, without special additions, to use motors on other principles of converting electricity in motion. But few know how the electric motor works and how it works.
Content
- How the device works
- Operation of a three-phase asynchronous motor
- Modern classification
- Key Features
- Ripple current units
- AC modifications
- Universal manifold equipment
How the device works
An alternating current electric motor contains fixed and movable parts. The first include:
- stator;
- inductor.
The stator finds application for machines synchronous and asynchronous type. The inductor is used in DC machines. The moving part consists of a rotor and an anchor. The first is used for synchronous and asynchronous devices, while the armature is used for equipment with constant rates. The function of the inductor lies on low power motors. Permanent magnets are often used here.
Speaking about how the electric motor is arranged, it is necessary to determine which class of equipment a particular model belongs to. In the design of an asynchronous motor, the rotor is:
- short-circuited;
- phase, that is, with a winding.
The latter type is used when it is required to reduce the starting current and 
adjust the speed asynchronous electric motor. Usually we are talking about crane electric motors, which are commonly used in crane installations.
The crane is flexible and is used in DC machines. It can be a generator or an engine, as well as a universal engine, operating on the same principle. It is used in power tools. In fact, a universal motor is the same constant rate motor in which sequential excitation occurs. The difference concerns only calculations of windings. There is no reactance here. It happens:
- capacitive;
- inductive.
That is why any power tool, if the electronic unit is removed from it, can also operate on direct current. But at the same time, the voltage in the network will be less. The principle of operation of an electric motor is determined in accordance with what components it consists of and for what purposes it is intended.
Operation of a three-phase asynchronous motor
When connected to the network, a rotating magnetic field is formed. It is noted in the stator and penetrates through the short-circuited rotor winding. It goes over into induction. After that, in accordance with Ampere's law, the rotor begins to rotate. The frequency of movement of this element depends on the frequency of the supply voltage and the number of magnetic poles represented in pairs.
The difference between the rotor speed and the stator magnetic field is expressed as slip. Engine called asynchronous, because the frequency of rotation of the magnetic field is consistent with the frequency of rotation of the rotor. The synchronous motor has differences in design. The rotor is supplemented with a permanent magnet or an electromagnet. It contains elements such as a squirrel cage for launching and permanent magnets. Also, their role can be played by electromagnets.
In an asynchronous motor, the stator magnetic field has the same speed as the rotor. For switching on, auxiliary-type asynchronous electric motors or a rotor with a squirrel-cage winding are used. Asynchronous motors have been widely used in all technical fields.
This is especially true in relation to three-phase motors, characterized by simple design. They are not only affordable, but also more reliable than electric ones. They require almost no care. The name asynchronous assigned to them is due to the asynchronous rotation of the rotor in such an engine. If there is no three-phase network, such a motor can be connected to a single-phase current network.
The stator of an asynchronous electric motor contains a package. It has varnished electrical steel sheets with a thickness of 0.5 mm. They have grooves where the winding is laid. The three phases of the winding are connected to each other by a triangle or star, which are offset by 120 degrees in space.
If we are talking about an electric motor rotor, in which there are slip rings in the grooves, a situation similar to the stator winding is noted here. This is relevant if it is turned on by a star or the initial ends of the phases are connected by three slip rings fixed on the shaft. When the engine is running, a rheostat can be connected to the winding phases to control the speed. After a successful run, the slip rings are short-circuited, and therefore the rotor winding performs the same functions as in the case of a short-circuited product.
Modern classification
According to the principle of the formation of torque, electric motors are divided into magnetoelectric and hysteresis. The last group differs in that the torque is formed here due to hysteresis when the rotor is excessively magnetized. Such motors are not considered classic and are not so common in the industry. The most widespread are magnetoelectric modifications, which are divided into two large groups, according to the energy consumed. These are AC and DC motors. Versatile models are also available that are capable of supplying both types of electric current.
Key Features
It would be correct to call these devices electrical nonphase. This is because the phases are switched here directly in the engine. Due to this, the motor is powered by a constant, as well as alternating types of current, with the same success. This group is divided according to the phase switching method and the presence of feedback. They are valve and collector.
With regard to the type of excitation, collector motors are divided into self-excited models, motors with independent excitation from permanent magnets and electromagnets. The first type, in turn, is classified into series, parallel, mixed excitation motors.
Brushless or valve products are powered by electricity. In them, phase switching occurs through a special electrical unit called an inverter. This process can be equipped with feedback when the rotor position sensor is put into motion or without feedback. Such a device can actually be positioned as an analogue of an asynchronous device.
Ripple current units
Such a motor is electric, and it is powered by a pulsating electric current. Its design features are similar to those of DC devices. Its constructive differences from a constant-performance motor are in the presence of laminated inserts for rectifying alternating current. It is used on electric locomotives with special installations. A characteristic feature is the presence of a compensation winding and a significant number of pole pairs.
AC modifications
The motor is a device powered by alternating current. These aggregates are asynchronous and synchronous. The difference is that in induction machines the magnetomotive force of the stator moves at the speed of rotation of the rotor. In asynchronous equipment, there is always a difference between the rotational speed of the magnetic field and the rotor.
The synchronous electric motor is powered by alternating current. The rotor here rotates in accordance with the movement of the magnetic field of the supply voltage. Synchronous electric motors are divided into modifications with field windings, with permanent magnets, as well as reactive modifications, hysteresis, stepping, hybrid reactive types of devices.
The so-called reactive-hysteresis type is also distinguished. Models with stepper units are also produced. Here, a certain rotor position is fixed by energizing certain winding zones. The transition to another position is achieved by removing the voltage from some windings and moving it to other areas. Valve reactive models of the electric type form power supply of windings by means of semiconductor elements. The asynchronous device has a rotor speed that is different from the frequency of the rotating magnetic field. It is created by the supply voltage. Such models are most widespread today.
Universal manifold equipment
Such a unit can operate on alternating and direct current. It is made with a serial excitation winding at power ratings up to 200 watts. The stator is made of special electrical steel. The excitation winding is carried out at a constant voltage indicator in full and partially at a variable indicator. The rated voltage for alternating electric current is 127 and 220 V, similar indicators for the constant parameter are 110 and 220 V. They are used in power tools and household appliances.
How an electric motor works depends on whether it belongs to a particular type of equipment. Modifications of alternating current with power supply from an industrial network of 50 Hz do not give a rotation frequency of more than 3000 rpm. That is why a collector motor of the electric type is used to obtain significant frequencies. It is also lighter and smaller in size than VARs of similar power.
In relation to them, special transmission mechanisms are used that convert the kinematic parameters of the mechanism to acceptable ones. When using frequency converters and in the presence of a high frequency network, AC motors are lighter and smaller than collector products.
The resource of asynchronous models with variable indicators is much higher than that of collector ones. It is determined by the condition of the bearings and the features of the winding insulation.
A synchronous motor, which has a rotor position sensor and an inverter, is considered the electronic counterpart of a brushed DC motor. In fact, it is a collector motor with stator windings connected in series. They are ideally optimized for use with a household power supply. Such a model, regardless of the polarity of the voltage, can be rotated in one direction, since the series connection of the windings and the rotor guarantees a pole change from magnetic fields. Accordingly, the result remains in one direction.
The stator of magnetic soft material is applicable for AC operation. This is possible if its magnetization reversal resistance is insignificant. To reduce eddy current losses, the stator is made of insulated plates. It turns out to be typeset. Its peculiarity is that the consumed current is limited due to the inductive resistance of the windings. Accordingly, the engine torque is estimated to be maximum and varies from 3 to 5. To approximate the mechanical characteristics of general-purpose motors, sectional windings are used. They have separate conclusions.
It is noteworthy that some types of bacteria use an electric motor made of several protein molecules to move. It is able to transform the energy of an electric current in the form of the movement of protons in the rotation of the flagellum.
The synchronous model of reciprocating motion works in such a way that the moving part of the device is equipped with permanent magnets. They are fixed to the curtain. By means of stationary elements, permanent magnets are under the influence of a magnetic field and move the rod in a reciprocating manner.
