If you look back and see how much has changed over the past few hundred years, it becomes unclear how people used to get along without the modern benefits of civilization. This applies not only to the living conditions of the housing plan, but also to improved vehicles. Just think, back in the 80s of the twentieth century, the cars that exist today might have seemed like an invention of the world of cinema, but now we know that some of them can be powered by electricity (), and others have already taken off above the ground (air cars).

Even though the latter option will not soon come into mass use, but as for cars equipped with an electric motor, they can already be found on city roads (take the same Toyota Prius). So what is so remarkable about the electric motor that it helped it gain universal recognition? To understand this issue, we will now analyze the historical path of development of the electric power unit, consider the features of its types, pay attention to the advantages and disadvantages, and also get acquainted with possible malfunctions and their causes.

1. History of the use of electric motors in car design

An electric motor is an electrical converter capable of transforming electricity into its mechanical version. A side effect of this action is the release of a certain amount of heat.

This device is used as a power plant in “eco-friendly” cars: electric cars, hybrids and cars powered by fuel cells. But if you don’t take into account the “heart” of the vehicle, low-power electric motors can be found even in the simplest gasoline sedan (for example, they are equipped with an electric door drive). The idea of ​​electric transport, in general terms, appeared back in 1831, immediately after Michael Faraday discovered the law of electromagnetic induction. The first engine, the operating principle of which was based on this discovery, was a unit developed in 1834 by the Russian physicist-inventor Boris Jacobi.

For the first time, vehicles equipped with electric motors used as a vehicle's power plant appeared in the 1880s and immediately gained universal popularity. This phenomenon can be explained quite simply: at the turn of the 19th and 20th centuries, internal combustion engines had a bunch of shortcomings that showed the new product in a very favorable light, since its characteristics were significantly superior to internal combustion engines. However, not much time passed and, thanks to the increase in power of gasoline and diesel engines, electric motors were forgotten for many decades. The next wave of interest in them returned only in the 70s of the twentieth century, during the era of the Great Oil Crisis, but again it did not reach mass production.

The first decade of the 21st century is the real Renaissance for electric motors in hybrid and electric vehicles. This was facilitated by several factors: on the one hand, the rapid development of computer technology and electronics made it possible to control and save battery power, and on the other hand, gradually increasing prices for oil fuel forced consumers to look for new, alternative sources of energy.

All in all, The entire history of the development of electric motors can be divided into three periods:

First (initial) period, covers 1821-1834 of the 19th century. It was at this time that the first physical instruments began to appear, with the help of which the continuous conversion of electrical energy into mechanical energy was demonstrated. Research by M. Faraday in 1821, which was carried out to study the interaction of conductors with current and a magnet, showed that an electric current can cause rotation of a conductor around a magnet or, conversely, a magnet around a conductor. The results of Faraday's experiments confirmed the real possibility of building an electric motor, and many researchers, even then, proposed various designs.

Second stage The development of electric motors began in 1834 and ended in 1860. It was characterized by the invention of designs with a rotating motion of a salient pole armature, but the shaft of such motors, as a rule, was sharply pulsating. The year 1834 was marked by the creation of the world's first electric DC motor, the creator of which (B.S. Jacobi) implemented in it the principle of direct rotation of the moving part of the power unit. In 1838, tests of this engine were carried out, for which it was installed on a boat and set free to sail along the Neva. Thus, Jacobi's development received its first practical application.

Third stage in the development of electric motors, it is generally accepted that the time period is from 1860 to 1887, which is associated with the development of a design with an annular non-salient pole armature and an almost constantly rotating torque. During this period, it is worth noting the invention of the Italian scientist A. Pacinotti, who developed the design of an electric motor consisting of a ring-shaped armature that rotated in the magnetic field of electric magnets. The current was supplied using rollers, and the electromagnetic winding was connected in series with the armature winding. In other words: the electric machine was excited sequentially. A distinctive feature of Pacinotti’s electric motor was the replacement of the salient-pole armature with a non-salient-pole one.

2. Types of electric motors

If we talk about modern electric motors, they have a fairly wide variety of types, and the most famous of them include:

- AC and DC motors;

Single-phase and multi-phase motors;

Stepper;

Valve and universal commutator motor.

DC and AC motors, as well as universal motors, are part of widely known magnetoelectric power units. Let's take a look at each type in more detail.

DC motors are electric motors that require a DC source to power them. In turn, based on the presence of a brush-commutator unit, this type is divided into brushed and brushless motors. Also, thanks to the named unit, the electrical connection of the circuits of the stationary and rotating parts of the unit is ensured, which makes it the most vulnerable and difficult to maintain element.

For the type of arousal, all collector types are again divided into subspecies:

- power plants with independent excitation (comes from permanent magnets and electromagnets);

Self-excited motors (divided into parallel, series and mixed excitation motors).

The brushless type of electric motors (they are also called “valve motors”) are devices presented in the form of a closed system that uses a rotor position sensor, a control system, and an inverter (power semiconductor converter). The operating principle of these motors is the same as that of representatives of the synchronous group.

An AC motor, as the name suggests, uses alternating current power. Based on the principle of operation, such devices are divided into synchronous and asynchronous motors. In synchronous motors, the rotor rotates along with the magnetic field of the incoming voltage, which allows these motors to be used at high power. There are two types of synchronous motors - stepper and switched reluctance motors.

Asynchronous electric motors, like the previous version, are representatives of alternating current electric motors, in which the rotor speed is slightly different from the similar frequency of the rotating magnetic field. Today, it is this type that is most often found in use. Also, all AC motors are divided into subtypes depending on the number of phases. Highlight:

- single-phase (manually started or equipped with a starting winding, or have a phase-shifting circuit);

Two-phase (including capacitor);

Three-phase;

Multiphase.

Universal type commutator motor is a device that can operate on both direct and alternating current. Such motors are equipped only with a series excitation winding with a power of up to 200 W. The stator has a laminated design and is made of special electrical steel. The field winding has two operating modes: with alternating current it is partially turned on, and with constant current it is fully turned on. Typically, such devices are used in power tools or some other household appliances.

An electronic analogue of a brushed DC motor is a synchronous motor that has a rotor position sensor and an inverter. Simply put, a universal brushed motor is a DC electric motor, the field windings of which are connected in series, ideally optimized for operation on alternating current. Regardless of the polarity of the incoming voltage, this type of power plant rotates in one direction, because due to the series connection of the rotor and stator windings, the poles of their magnetic fields change simultaneously, which means that the resulting torque continues to be directed in one direction.

To ensure operation on alternating current, a stator made of soft magnetic material with low hysteresis (resistance to the magnetization reversal process) is used, and to reduce losses due to eddy flows, the stator design is made of insulated plates. Dignity The operation of an AC electric motor is that at low speeds (starting, restarting), the current consumption, and, accordingly, the maximum torque of the motor is limited by the inductive reactance of the stator windings.

In order to bring the mechanical characteristics of general-purpose motors closer together, sectioning the stator windings is often used, that is, separate terminals are created for connecting alternating current and the number of winding turns is reduced.

The operating principle of a reciprocating synchronous electric motor is based on the fact that the moving part of the motor is presented in the form of permanent magnets, which are attached to a rod. An alternating current passes through the stationary windings, and permanent magnets, influenced by the magnetic field, move the rod in a reciprocating manner.

Another classification, which allows us to distinguish several types of electric motors, is based on the degree of environmental protection. Based on this parameter, electrical power plants can be protected, closed and explosion-proof.

Protected versions are closed with special flaps that protect the mechanism from the ingress of various foreign objects. They are used where there is no high humidity and no special air composition (free from dust, smoke, gases and chemicals). Closed types are placed in a special shell that prevents the entry of gases, dust, moisture and other elements that can harm the motor mechanism. These devices can be sealed or non-sealed.

Explosion-proof mechanisms. They are installed in a housing that, in the event of a motor explosion, will be able to protect the remaining parts of the device from damage, thereby preventing the occurrence of a fire.

When choosing an electric motor, pay attention to the operating environment of the mechanism. If, for example, the air does not contain any foreign impurities that could harm it, then instead of a heavy and expensive closed engine it is better to purchase a protected one. A separate point is also worth remembering about the built-in electric motor, which does not have its own shell and is part of the design of the working mechanism.

3. Advantages and disadvantages of electric motors

Like any other device, an electric motor is not “sinless”, which means that, along with undeniable advantages, it also has certain disadvantages. Let's start with the positive aspects of use, which include:

1. No friction losses during transmission;

2. The efficiency of a traction electric motor reaches 90-95%, while that of an internal combustion engine is only 22-60%;

3. The maximum torque value of the traction motor (traction motor) is achieved already from the beginning of movement, at the moment the engine starts, therefore, a gearbox is simply not needed here.

4. The cost of operation and maintenance is comparatively lower than that of internal combustion engines;

5. No toxic exhaust gases;

6. High level of environmental friendliness (petroleum fuels, antifreezes and motor oils are not used);

7. Minimum possibility of explosion in case of accident;

8. Simple design and control, high level of reliability and durability of the undercarriage;

9. Possibility of recharging from a regular household outlet;

10. Reduced noise with fewer moving parts and mechanical gears;

11. Increased smoothness of operation with a wide frequency range of changes in the rotation of the motor shaft;

12. Possibility of recharging during regenerative braking;

13. Possibility of using the electric motor itself as a brake (electromagnetic brake function). There are no representatives in the mechanical version, which helps to avoid friction and, consequently, wear of the brakes.

Considering the above, we can come to the logical conclusion that a car equipped with an electric motor is approximately 3-4 times more efficient than its gasoline counterparts. However, as we have already said, there are still disadvantages:

- the operating time of the engine is limited by the maximum possible volume of batteries, that is, compared to internal combustion engines, they have a much shorter mileage per fill-up;

Higher cost, but there is a chance that with the start of mass mass production the price will decrease;

The need to use additional accessories (for example, fairly heavy batteries weighing from 15 to 30 kilograms and special chargers that are intended for deep discharge).

As you can see, there are not so many main shortcomings, and over time their number will continue to fall rapidly, because automotive engineers and designers will “work on the mistakes” with each subsequent product release.

4. Identifying and troubleshooting motor problems

Unfortunately, for all its positive aspects, the electric motor, like any other device, is not protected from breakdowns and periodically fails. The most common malfunctions of electric motors include:

When starting the engine it makes a loud noise.Possible reasons such a phenomenon may be a decrease or complete absence of voltage in the supply network; incorrect location of the beginning and end of the stator winding phase; motor overload or malfunction in the drive mechanism. Naturally, to eliminate the problems that have arisen, you need to either find and eliminate the malfunction, or reconnect, but according to the correct circuit, or reduce the load or eliminate the malfunction in the drive mechanism.

The running engine suddenly stops. Possible reasons: the voltage supply has stopped; there were malfunctions in the operation of switchgear equipment and the power supply network; the motor or drive mechanism is jammed; the protection system worked. To eliminate breakdowns you should: find and repair a break in the circuit; eliminate malfunctions in the equipment of the switchgear and power supply network; repair the drive mechanism; carry out stator diagnostics and, if necessary, carry out repair measures.

The shaft rotates, but cannot reach normal speed. Possible reasons: during the acceleration of the car, one of the phases turned off; the network voltage has decreased; the engine is under excessive load. Raising the voltage will help eliminate any malfunctions; connecting the disconnected phase and eliminating motor overload.

The electric motor is overheating. Possible reasons: there is an overcurrent; the voltage in the network has decreased or increased; the ambient temperature has increased; normal ventilation is disrupted (ventilation ducts are clogged); The normal operation of the drive mechanism has been disrupted.

Ways to solve the problem: ensure a normal load level; set the optimal permissible temperature; clean the ventilation ducts; repair the drive mechanism.

The motor makes a loud noise and does not reach normal speed.Possible reasons: an interturn short circuit has occurred in the stator winding; grounding the winding of one phase in two places at once; the appearance of a short circuit between phases; break of some phase. In this case, there is only one way out - you will have to change the stator.

Increased vibration of a running motor.Possible reasons: low foundation rigidity; errors in compatibility of the drive shaft with the motor shaft; The coupling or drive is not balanced enough. Way out of this situation: increase rigidity; balance and improve relevance.

Increased heating of bearings. Possible reasons: bearing damage; Incorrect alignment of the motor with the drive mechanism. Correct installation of the engine or replacement of the bearing will help solve the problems that have arisen.

Reduced winding insulation resistance. The causes of malfunctions in this case lie in contamination or dampness of the windings, and drying the parts will help eliminate them.

When choosing a brushless motor for their designs, engineers have several options. A wrong choice can lead to project failure not only at the development and testing stage, but also after entering the market, which is highly undesirable. To facilitate the work of engineers, we will make a brief description of the advantages and disadvantages of the four most popular types of brushless electrical machines: asynchronous electric motor (AM), permanent magnet motor (PM), synchronous reluctance motors (SRM), switched reluctance motors (VRM).

Content:

Asynchronous electric motors

Asynchronous electric machines can safely be called the backbone of modern industry. Due to their simplicity, relatively low cost, minimal maintenance costs, and the ability to operate directly from industrial AC networks, they have become firmly entrenched in modern production processes.

Today there are many different ones that allow you to regulate the speed and torque of an asynchronous machine over a wide range with good accuracy. All these properties allowed the asynchronous machine to significantly push traditional commutator motors out of the market. That is why adjustable asynchronous electric motors (AM) are easy to find in a wide variety of devices and mechanisms, such as electric drives of washing machines, fans, compressors, blowers, cranes, elevators and many other electrical equipment.

The IM creates torque due to the interaction of the stator current with the induced rotor current. But the rotor currents heat it up, which leads to heating of the bearings and a decrease in their service life. Replacing with copper does not eliminate the problem, but leads to an increase in the cost of the electric machine and may impose restrictions on its direct start-up.

The stator of an asynchronous machine has a rather large time constant, which negatively affects the response of the control system when the speed or load changes. Unfortunately, losses associated with magnetization do not depend on the machine load, which reduces the efficiency of the IM when operating at low loads. Automatic reduction of stator flux can be used to solve this problem - this requires a quick response of the control system to load changes, but as practice shows, such correction does not significantly increase efficiency.

At speeds exceeding the rated speed, the stator field weakens due to the limited supply voltage. The torque begins to drop as more rotor current will be required to maintain it. Consequently, controlled IMs are limited to a speed range to maintain a constant power of approximately 2:1.

Mechanisms that require a wider control range, such as CNC machines, traction electric drives, can be equipped with specially designed asynchronous electric motors, where, to increase the control range, they can reduce the number of winding turns, while reducing torque values ​​at low speeds. It is also possible to use higher stator currents, which requires the installation of more expensive and less efficient inverters.

An important factor when operating an IM is the quality of the supply voltage, because the electric motor has maximum efficiency when the supply voltage is sinusoidal. In reality, the frequency converter provides a pulsed voltage and current similar to a sinusoidal one. Designers should keep in mind that the efficiency of the inverter-inverter system will be less than the sum of the efficiency of the converter and the motor separately. Improvements in the quality of the output current and voltage are increased by increasing the carrier frequency of the converter, this leads to a reduction in losses in the motor, but at the same time losses in the inverter itself increase. One popular solution, especially for industrial high-power electric drives, is to install filters between the frequency converter and the asynchronous machine. However, this leads to an increase in cost, installation dimensions, as well as additional power losses.

Another disadvantage of AC induction machines is that their windings are distributed over many slots in the stator core. This results in long end turns, which increase the size and energy loss of the machine. These issues are excluded from IE4 standards or IE4 classes. Currently the European standard (IEC60034) specifically excludes any motors requiring electronic control.

Permanent magnet motors

Permanent magnet motors (PMMS) produce torque through the interaction of stator currents with permanent magnets inside or outside the rotor. Electric motors with surface magnets are low-power and are used in IT equipment, office equipment, and automobile transport. Integrated magnet motors (IPMs) are common in high-power machines used in industrial applications.

Permanent magnet (PM) motors can use concentrated (short pitch) windings if torque ripple is not critical, but distributed windings are the norm in PMs.

Since PMMS do not have mechanical commutators, converters play an important role in the winding current control process.

Unlike other types of brushless electric motors, PMMS do not require excitation current to maintain rotor flux. Consequently, they are capable of delivering maximum torque per unit volume and may be the best choice when weight and size requirements are at the forefront.

The greatest disadvantages of such machines include their very high cost. High-performance permanent magnet electric machines use materials such as neodymium and dysprosium. These materials are classified as rare earths and are mined in geopolitically unstable countries, which leads to high and unstable prices.

Also, permanent magnets add performance when working at low speeds, but are an “Achilles heel” when working at high speeds. For example, as the speed of a machine with permanent magnets increases, its EMF will also increase, gradually approaching the supply voltage of the inverter, while it is not possible to reduce the flux of the machine. Typically, the rated speed is the maximum for a PM with a surface magnetic design at the rated supply voltage.

At speeds above the rated speed, for electric motors with permanent magnets of the IPM type, active field suppression is used, which is achieved by manipulating the stator current using a converter. The speed range over which the motor can operate reliably is limited by approximately 4:1.

The need for field weakening depending on speed leads to losses independent of torque. This reduces efficiency at high speeds, and especially at light loads. This effect is most relevant when using PM as a traction automobile electric drive, where high speed on the highway inevitably entails the need to weaken the magnetic field. Developers often advocate the use of permanent magnet motors as traction electric drives for electric vehicles, but their effectiveness when working in this system is quite questionable, especially after calculations associated with real driving cycles. Some electric vehicle manufacturers have made the transition from PM to asynchronous electric motors as traction motors.

Also, significant disadvantages of electric motors with permanent magnets include their difficulty in controllability under fault conditions due to their inherent back-EMF. Current will flow in the windings, even when the converter is turned off, as long as the machine is rotating. This can lead to overheating and other unpleasant consequences. Loss of control over a weakened magnetic field, such as during a power outage, can lead to uncontrolled generation of electrical energy and, as a result, a dangerous increase in voltage.

Operating temperatures are another not the strongest side of PM, except for machines made of samarium-cobalt. Also, large inrush currents of the inverter can lead to demagnetization.

The maximum speed of PMMS is limited by the mechanical strength of the magnets. If the PM is damaged, its repair is usually carried out at the manufacturer, since removing and safely processing the rotor is practically impossible under normal conditions. And finally, recycling. Yes, this is also a bit of a hassle once the machine reaches the end of its life, but the presence of rare earth materials in this machine should make this process easier in the near future.

Despite the disadvantages listed above, permanent magnet motors are unsurpassed in terms of low-speed, small-sized mechanisms and devices.

Synchronous jet motors

Synchronous reluctance motors are always paired with a frequency converter and use the same type of stator flux control as a conventional IM. The rotors of these machines are made of thin-sheet electrical steel with slots punched in such a way that they are magnetized less on one side than on the other. The rotor's magnetic field tends to "couple" with the rotating magnetic flux of the stator and creates torque.

The main advantage of reluctance synchronous electric motors is the low losses in the rotor. Thus, a well-designed synchronous reluctance machine operating with the right control algorithm is quite capable of meeting the European premium IE4 and NEMA standards without using permanent magnets. The reduction in the rotor increases torque and increases power density compared to asynchronous machines. These motors have low noise levels due to low torque ripple and vibration.

The main disadvantage is the low power factor compared to an asynchronous machine, which results in higher power consumption from the network. This increases the cost and poses a difficult question to the engineer, is it worth using a reactive machine or not for a particular system?

The complexity of manufacturing the rotor and its fragility make it impossible to use jet motors for high-speed operations.

Synchronous reluctance machines are well suited for a wide range of industrial applications that do not require high overloads or high rotation speeds, and are increasingly being used for variable speed pumps due to their increased efficiency.

Switched reluctance motors

A switched reluctance motor (SRM) creates torque by attracting the magnetic fields of the rotor teeth to the magnetic field of the stator. Switched reluctance motors (WRM) have a relatively small number of stator winding poles. The rotor has a toothed profile, which simplifies its design and improves the generated magnetic field, unlike reluctance synchronous machines. Unlike synchronous reluctance motors (SRM), WRMs use pulsed DC excitation, which requires a special converter for their operation.

To maintain the magnetic field in the VRM, excitation currents are required, which reduces the power density compared to electric machines with permanent magnets (PM). However, they still have smaller overall dimensions than conventional ADs.

The main advantage of switched reluctance machines is that the magnetic field weakens naturally when the excitation current decreases. This property gives them a great advantage in the control range at speeds above the nominal (the range of stable operation can reach 10:1). High efficiency is present in such machines when operating at high speeds and with low loads. Also, VRDs are capable of providing surprisingly constant efficiency over a fairly wide control range.

Switched reluctance machines also have fairly good fault tolerance. Without permanent magnets, these machines do not generate uncontrolled current and torque during malfunctions, and the independence of the VRM phases allows them to operate with a reduced load, but with increased torque ripples when one of the phases fails. This property can be useful if designers want increased reliability of the system being developed.

The simple design of the VRD makes it durable and inexpensive to manufacture. No expensive materials are used in its assembly, and the non-alloy steel rotor is excellent for harsh climate conditions and high rotation speeds.

A VRD has a power factor lower than PM or IM, but its converter does not need to create a sinusoidal output voltage for efficient operation of the machine; accordingly, such inverters have lower switching frequencies. As a result, lower losses in the inverter.

The main disadvantages of switched reluctance machines are the presence of acoustic noise and vibration. But these shortcomings can be combated quite well by more carefully designing the mechanical part of the machine, improving electronic control, and also mechanically combining the engine and the working body.

The article discusses various types of electric motors, their advantages and disadvantages, and development prospects.

Types of electric motors

Electric motors are currently an indispensable component of any production. They are also used very often in public utilities and in everyday life. For example, these are fans, air conditioners, heating pumps, etc. Therefore, a modern electrician needs to have a good understanding of the types and design of these units.

So, we list the most common types of electric motors:

1. DC electric motors, with a permanent magnet armature;

2. DC electric motors, with an armature having an excitation winding;

3. AC synchronous motors;

4. AC asynchronous motors;

5. Servo motors;

6. Linear asynchronous motors;

7. Motor rollers, i.e. rollers containing electric motors with gearboxes;

8. Valve electric motors.

DC motors

This type of motor was previously used very widely, but now it is almost completely replaced by asynchronous electric motors, due to the comparative cheapness of using the latter. A new direction in the development of DC motors is DC motors with permanent magnet armatures.

Synchronous motors

Synchronous electric motors are often used for various types of drive operating at a constant speed, i.e. for fans, compressors, pumps, DC generators, etc. These are motors with a power of 20 - 10000 kW, for rotation speeds of 125 - 1000 rpm.

Motors differ from generators structurally in the presence on the rotor, necessary for asynchronous starting, of an additional short-circuited winding, as well as a relatively smaller gap between the stator and the rotor.

Synchronous motors have efficiency higher, and the mass per unit of power is less than that of asynchronous ones at the same rotation speed. A valuable feature of a synchronous motor compared to an asynchronous one is the ability to regulate it, i.e. cosφ due to changes in the excitation current of the armature winding. Thus, it is possible to make cosφ close to unity in all operating ranges and, thereby, increase efficiency and reduce losses in the power grid.

Asynchronous motors

Currently, this is the most commonly used type of engine. An induction motor is an alternating current motor whose rotor speed is lower than the speed of the magnetic field created by the stator.

By changing the frequency and duty cycle of the voltage supplied to the stator, you can change the rotation speed and torque on the motor shaft. The most commonly used are asynchronous motors with squirrel-cage rotor. The rotor is made of aluminum, which reduces its weight and cost.

The main advantages of such engines are their low price and light weight. Repairing electric motors of this type is relatively simple and cheap.

The main disadvantages are the low starting torque on the shaft and the high starting current, 3-5 times higher than the operating current. Another big disadvantage of an asynchronous motor is its low efficiency at partial loads. For example, at a load of 30% of the rated load, efficiency can drop from 90% to 40-60%!

The main way to combat the shortcomings of an asynchronous motor is to use a frequency drive. converts 220/380V network voltage into pulsed voltage of variable frequency and duty cycle. Thus, it is possible to vary the speed and torque on the engine shaft within a wide range and get rid of almost all of its inherent defects. The only “fly in the ointment” in this “barrel of honey” is the high price of the frequency drive, but in practice all costs are recouped within a year!

Servo motors

These motors occupy a special niche, they are used where precision changes in position and speed are required. These are space technology, robotics, CNC machines, etc.

Such engines are distinguished by the use of small-diameter anchors, because small diameter means low weight. Due to the low weight, it is possible to achieve maximum acceleration, i.e. fast movements. These motors usually have a system of feedback sensors, which makes it possible to increase the accuracy of movement and implement complex algorithms for movement and interaction of various systems.

Linear asynchronous motors

A linear induction motor creates a magnetic field that moves a plate in the motor. The movement accuracy can be 0.03 mm per meter of movement, which is three times less than the thickness of a human hair! Typically a plate (slider) is attached to a mechanism that must move.

Such motors have a very high travel speed (up to 5 m/s), and therefore high performance. The movement speed and pitch can be changed. Since the engine has a minimum of moving parts, it has high reliability.

Motor rollers

The design of such rollers is quite simple: inside the drive roller there is a miniature DC electric motor and gearbox. Motor rollers are used on various conveyors and sorting lines.

The advantages of motor rollers are low noise level, higher efficiency compared to an external drive, the motor roller practically does not require maintenance, since it only works when the conveyor needs to be moved, its resource is very long. When such a roller fails, it can be replaced with another in a minimum amount of time.

Valve motors

A valve motor is called any motor in which the operating modes are controlled using semiconductor (valve) converters. As a rule, this is a synchronous motor with permanent magnet excitation. The motor stator is controlled by a microprocessor controlled inverter. The engine is equipped with a sensor system to provide feedback on position, speed and acceleration.

The main advantages of valve motors are:

1. Non-contact and absence of components requiring maintenance,

2. High resource;

3. Large starting torque and high torque overload capacity (5 times or more);

4. High performance during transient processes;

5. A huge range of speed adjustments of 1:10000 or more, which is at least two orders of magnitude higher than that of asynchronous motors;

6. The best indicators in terms of efficiency and cosφ, their efficiency at all loads exceeds 90%. While for asynchronous motors the efficiency at half loads can drop to 40-60%!

7. Minimum no-load currents and starting currents;

8. Minimum weight and dimensions;

9. Minimum payback period.

According to their design features, such motors are divided into two main types: contactless DC and AC motors.

The main direction of improving switched-type electric motors at the moment is the development of adaptive sensorless control algorithms. This will reduce the cost and increase the reliability of such drives.

In such a small article, of course, it is impossible to reflect all aspects of the development of electric drive systems, because This is a very interesting and fast-growing area in technology. Annual electrical exhibitions clearly demonstrate the constant growth in the number of companies seeking to master this area. The leaders of this market are, as always, Siemens AG, General Electric, Bosch Rexroth AG, Ansaldo, Fanuc, etc.

The main difference between an inverter motor and a conventional electric motor is that it does not have brushes. The units are used in refrigerators, automatic washing machines, and air conditioners. The converter, which acts as a power source for the motor, converts alternating voltage into direct voltage. Resulting DC Current converted to alternating current of a given frequency

The main parts are the motor itself and the frequency converter, which ensures the operating principle of the motor. The frequency converter is used to regulate the speed of the motor by creating the required voltage frequency at the output of the converter. The range of output frequency in converters varies widely, and its maximum values ​​can be tens of times higher than the frequency of the supply network.

In the inverter converter, double voltage conversion occurs. The sinusoidal voltage at the converter input is first rectified in the rectifier block, filtered and smoothed by electrical filter capacitors. Next, from the obtained constant voltage using control circuits and output electronic keys, a sequence of controlled pulses of the required shape and frequency is specified. Using pulses, an alternating voltage of the required magnitude and frequency is created, which is generated at the output of the converter.

The sinusoidal alternating current generated by the converter on the windings of the electric motor is formed as a pulse-frequency or pulse width modulation. Electronic switches for converters are, for example, switchable GTO thyristors, their upgraded versions IGCT, SGCT, GCT and IGBT transistors.

The motor consists of a stator with small field windings, the number of which is a multiple of three. The stator rotates a rotor with permanent magnets attached to it. The number of magnets is three times less than the number of field windings. There is no commutator-brush assembly in such an engine.

All this is an inverter electric motor, the operating principle of which is based on the interaction magnetic fields of the stator and rotor. The rotating electromagnetic field of the stator created by the converter causes the frequency rotor to rotate at the same frequency. So, the motor is controlled by an inverter converter

.

Pros and cons of the device

The inverter type motor is compact and highly reliable. Its other advantages include:

Despite a lot of advantages, the engine has disadvantages. The most significant of them include:

• High price of the converter.
• The need for expensive repairs in case of breakdown.
• The need to maintain a certain voltage level in the network.
• Impossibility of operation due to changes in the supply voltage.

Using the motor in a washing machine

The inverter motor, developed in 2005 by engineers of the Korean concern LG, brought the production of washing machines to a new level. Compared to its predecessors, the new engine has better technical specifications, greater wear resistance, lasts longer. Therefore, inverter motors are gaining more and more popularity and their production is growing. But is everything so rosy?

Advantages and disadvantages of the washing process:

It is recommended to pay attention to the functionality of the equipment. The inverter motor itself does not guarantee perfect washing. If you are planning to buy a washing machine with an inverter motor, purchase the equipment exclusively from trusted outlets. Most often, cheap models - this is a banal fake, and it is unlikely that their characteristics will correspond to those declared by the manufacturer.

Hi all. Glad to see you on my website. The topic of today's article: the design and principle of operation of asynchronous electric motors. I would also like to say a little about ways to adjust their rotation speed, and list their main advantages and disadvantages.

Previously, I have already written articles regarding asynchronous electric motors. If anyone is interested, you can read it. Here is the list:

Well, now let's move on to the topic of today's article.

At the present time, it is very difficult to imagine how all industrial enterprises would exist if there were no asynchronous machines. These engines are installed almost everywhere. Even at home, every person has such an engine. It can be on your washing machine, on a fan, on a pumping station, in an extractor hood, and so on.

In general, an asynchronous electric motor is a colossal breakthrough in global industry. Worldwide, they produce more than 90 percent of all engines produced.

An asynchronous electric motor is an electrical machine that converts electrical energy into mechanical energy. That is, it consumes electric current, and in return they provide torque, with which you can rotate many units.

And the word “asynchronous” itself means non-simultaneous or not coinciding in time. Because in such engines the rotor speed is slightly behind the rotation speed of the stator electromagnetic field. This lag is also called sliding.

This sliding is designated by the letter: S

And the slip is calculated using the following formula: S = (n1 - n2)/ n1 - 100%

Where, n1 is the synchronous frequency of the stator magnetic field;

n2 is the shaft rotation speed.

The device of an asynchronous electric motor.

The engine consists of the following parts:

1. Stator with windings. Or a frame inside which there is a stator with windings.

2. Rotor. This is if it is short-circuited. And if it is phase, then we can say that it is an armature or even a collector. I think there will be no mistakes.

3. Bearing shields. On powerful engines, there are also bearing caps with seals at the front.

4. Bearings. They can be sliding or rolling, depending on the design.

5. Cooling fan. Made from plastic or metal.

6. Fan shroud. Has slots for air supply.

7. Borno or terminal box. For connecting cables.

These are all its main details, but depending on the type, type and design it may vary slightly.

Asynchronous electric motors are mainly produced in two types: three-phase and single-phase. In turn, three-phase ones are further divided into subtypes: with a squirrel-cage rotor or a phase rotor.

The most common are three-phase with a squirrel-cage rotor.

The stator has a round shape and is assembled from sheets of special steel, which are insulated together, and this assembled structure forms a core with grooves. Windings with a special winding wire insulated with varnish are placed in the grooves of the core. This wire is cast mainly from copper, but also from aluminum. If the engine is very powerful, then I make the windings with a busbar. The windings are laid so that they are shifted relative to each other by 120 degrees. The stator windings are connected in a star or triangle.

The rotor, as I already wrote above, can be short-circuited or phase.

The short-circuited shaft is a shaft onto which sheets of also special steel are placed. These typesetting sheets form a core into the grooves of which molten aluminum is poured. This aluminum flows evenly along the grooves and forms rods. And at the edges of these rods they are closed with aluminum rings. It turns out to be a kind of “squirrel cage”.

The phase rotor is a shaft with a core and three windings. Some ends, which are usually connected in a star, and the second three ends are connected to slip rings. And electric current is supplied to these rings using brushes.

If you add a load rheostat to the circuit of phase windings, and increase the active resistance when starting the engine, then in this way you can reduce large starting currents.

Operating principle.

When electric current is applied to the stator windings, an electric current occurs in these windings. As you remember from the words written above, our phases are shifted relative to each other by 120 degrees. And this flow in the windings begins to rotate.

And when the stator magnetic flux rotates, an electric current and its own magnetic field appear in the rotor windings. These two magnetic fields begin to interact and cause the rotor of the electric motor to rotate. This is if the rotor is short-circuited.

Based on the robot principle, watch the video clip.

Well, with a wound rotor, the principle is essentially the same. Voltage is supplied to the stator and rotor. Two magnetic fields appear, which begin to interact and rotate the rotor.

Advantages and disadvantages of asynchronous motors.

The main advantages of an asynchronous electric motor with a squirrel cage rotor:

1. A very simple device, which reduces the cost of its production.

2. The price is much less compared to other engines.

3. Very simple launch scheme.

4. The shaft rotation speed practically does not change with increasing load.

5. Tolerates short-term overloads well.

6. Possibility of connecting three-phase motors to a single-phase network.

7. Reliability and ability to operate in almost any conditions.

8. Has a very high efficiency and cos φ.

Flaws:

1. It is not possible to control the rotor speed without loss of power.

2. If you increase the load, the torque decreases.

3. The starting torque is very small compared to other machines.

4. When underloaded, the cos φ indicator increases

5. High starting currents.

Advantages of wound rotor motors:

1. Compared to squirrel-cage motors, it has a fairly large torque. This allows it to run under load.

2. It can work with a slight overload, and at the same time the shaft rotation speed practically does not change.

3. Small starting current.

4. Automatic starting devices can be used.

Flaws:

1. Large dimensions.

2. Efficiency and cos φ indicators are lower than those of squirrel-cage motors. And when underloaded, these indicators have a minimum value

3. The brush mechanism needs to be serviced.

This is where I will end my article. If you found it useful, then share it with your friends on social networks. If you have questions, ask them in the comments and subscribe to updates. Bye.

Best regards, Alexander!