NAMI-0189E is shown in fig. 3.6.
Rice. 3.6. Scheme of the electric drive with switching of sections of the battery and regulation by excitation
The traction motor M is powered by two traction battery units GB1 and GB2, which are connected to its circuit either in parallel or in series with the help of KB contactors. In the armature circuit of the motor, in addition, there are starting resistors R1 and R2, shunted by the KSh contactor. The motor excitation current is regulated by a thyristor pulse converter containing the main thyristor V2 and switching - V3. The engine is reversed by the KR contactor, which switches the voltage polarity on the OB excitation winding. The operating modes of the electric drive are set by a special controller. This device, controlled by the driver, contains mode switches, as well as an inductive adjuster, the position of which determines the value of the excitation current using the control unit B U. In turn, the motor excitation current determines the magnitude of the armature current
(3.3)
as well as the dynamic moment on the motor shaft
In steady-state operating modes of the engine Mdyn = 0 and from expression (3.4) it follows that the excitation current determines the rotational speed according to the formula
(3.5)
where UП is the supply voltage of the motor armature circuit; and
#1 - when KB is off
#2 - when KB is on
With the help of the control unit BU negative feedback according to the battery current and the direction on the motor excitation winding, the set values of the excitation current and battery current are stabilized, and thus the driving modes according to expressions (3.4) and (3.5).
When starting the electric car, the battery blocks are connected in parallel, by turning on the contactor K, the engine starts at the first rheostatic stage through the resistor RI. The excitation of the engine is set close to the maximum. Further pressing the accelerator pedal and thereby affecting the controller during acceleration causes the second rheostat stage to be turned on by connecting resistors RI resistor #2 in parallel through thyristor VI. When the starting current decreases, the contactor KSH turns on and short-circuits the starting rheostats. Thyristor VI then returns to the off state. Further control is performed by changing the excitation current. When the speed reaches 30 km/h, the controller switches the battery blocks to a serial connection and continues control by changing the excitation current.
Regenerative braking occurs with an increase in the excitation current and an increase due to this motor emf. The battery charge current begins to flow through the diode V both when the blocks are connected in series and in parallel. The range of possible regenerative regenerative braking dr depends on the motor excitation flux reduction used and can be determined from the following relationship.
Progress does not stand still and everything moves forward and develops. This also applies to electric drive systems. The advent of frequency-controlled electric drives and various ways management of them makes its own adjustments to the degree of development of these devices. And this has led to the fact that the asynchronous electric drive is gradually beginning to replace DC machines in traction systems– electric trains, trolleybuses, mainline electric locomotives. Automotive equipment is no exception.
Modern realities are such that the operation and maintenance of DC drives in excavators and heavy dump trucks is associated with a number of inconveniences, but the modern development of science, as well as the availability of the necessary element base, has greatly facilitated the solution of this problem. That is why in 2005 the designers " power machines» started to create a new line of electric drives - asynchronous (frequency). They are developed specifically for loaders and mining dump trucks manufactured by OJSC BELAZ, as well as powerful excavators manufactured by Uralmash and Izhorskiye Zavody.
Traction asynchronous electric drive
System asynchronous motor– the frequency converter is by far the most complex of the electric drive systems. Traction asynchronous drive is based on vector control. It is also necessary to provide a multi-level protection and alarm system for safe work systems, and, accordingly, systems software and visualization to enable system monitoring and settings.
But in addition to a significant complication of the control system of a traction asynchronous electric drive, it has significant advantages compared to the old DC systems that were used in mining trucks JSC "BELAZ":
- The absence of a collector-brush assembly inherent in the system, which significantly reduces operating costs.
- Besides, traction motor located in such a way that the electrician needs to literally squeeze through to it, which also places special demands on the maintenance personnel.
- If the condition of the collector is unsatisfactory, more complex repair work- and this is downtime and losses. IN asynchronous machine there is no collector.
- When operating on direct current, switching between traction and braking modes was carried out mechanically - using contactors. In a system with AD, switching is performed by power valves, using FC control algorithms.
Price. Pros and cons
Traction cost asynchronous electric drive quite high and it's intimidating. But in addition to the costs of acquisition, installation and commissioning, there are also costs for operation. Due to the fact that the brush-collector assembly in the IM with a short-circuit rotor
missing, the operating costs are significantly reduced. After all, the main weak point DC machines is precisely the collector assembly, which must be periodically cleaned, brushes changed, and sometimes the collector itself. Also, asynchronous circuits are smaller in overall dimensions than DPTs. The frequency converters are equipped with diagnostic and alarm devices to assist in troubleshooting. Also, if an element fails, it is enough to replace the cell or power module device and it's ready to go.
Auxiliary electrical equipment call a group of auxiliary devices and devices that provide heating and ventilation of the cabin and body, cleaning the windows of the cabin and headlights, sound alarms, radio reception and other auxiliary functions.
Development trends various systems vehicle, associated with an increase in efficiency, reliability, comfort and traffic safety, lead to the fact that the role of electrical equipment, in particular the electric drive auxiliary systems, is steadily increasing. If 25...30 years ago on production cars there were practically no mechanisms with an electric drive, at present, even trucks are equipped with at least 3 ... 4 electric motors, and cars - 5 ... 8 or more, depending on the class.
Electric drive called an electromechanical system consisting of an electric motor (or several electric motors), a transmission mechanism to working machine and all motor control equipment. The main devices of the car, where the electric drive is used, are heaters and fans of the passenger compartment, starting heaters, glass and headlight cleaners, mechanisms for lifting glasses, antennas, moving seats, etc.
The duration of work and its nature determine the operating mode of the drive. For the electric drive, it is customary to distinguish three main modes of operation: continuous, short-term and intermittent.
Continuous mode is characterized by such a duration at which, during the operation of the electric motor, its temperature reaches a steady value. As an example of mechanisms with a long operating mode, heaters and fans of the car interior can be mentioned.
Momentary mode has a relatively short operating period and the engine temperature does not have time to reach a steady value. A break in the operation of the actuator is sufficient for the engine to cool down to a temperature environment. This mode of operation is typical for most various devices short-term action: lifting windows, driving antennas, moving seats, etc.
Intermittent mode characterized by a working period that alternates with pauses (stop or idling), and in none of the periods of operation the temperature of the engine reaches a steady-state value, and during the removal of the load, the engine does not have time to cool down to the ambient temperature. An example of car devices operating in this mode can be windshield wipers (in the appropriate modes), windshield washers, etc.
characteristic feature for the intermittent mode is the ratio of the working part of the period T" to the entire period T. This indicator is called the relative duration of work ETC or relative duty cycle PV, measured as a percentage.
The requirements for electric motors installed in a particular vehicle unit are particularly specific and are determined by the operating modes of this unit. When choosing the type of motor, it is necessary to compare the operating conditions of the drive with the features of the mechanical characteristics various kinds electric motors. It is customary to distinguish between natural and artificial mechanical characteristics of the engine. The first corresponds to the nominal conditions for its inclusion, the normal wiring diagram and the absence of any additional elements in the motor circuits. Artificial characteristics are obtained by changing the voltage on the motor, including additional elements in the motor circuit and connecting these circuits according to special schemes.
One of the most promising directions in the development of the electric drive of auxiliary systems of a car is the creation of electric motors with a power of up to 100 W with excitation from permanent magnets.
Application permanent magnets allows you to significantly improve the technical and economic performance of electric motors: reduce weight, dimensions, improve efficiency. The advantages include the absence of excitation windings, which simplifies internal connections, increases the reliability of electric motors. In addition, due to independent excitation, all permanent magnet motors can be reversible.
A typical design of a permanent magnet motor used in heaters is shown in Fig. 7.1 .
Permanent magnets 4 are fixed in the housing 3 with the help of two steel flat springs 6 attached to the body. Anchor 7 the electric motor rotates in two self-aligning plain bearings 5 . Graphite brushes 2 pressed against the manifold by springs 1, made of copper strip and milled into individual lamellas.
The principle of operation of electric machines with permanent magnets is similar to the well-known principle of operation of machines with electromagnetic excitation- in the electric motor, the interaction of the fields of the armature and the stator creates a torque. The source of magnetic flux in such electric motors is a permanent magnet. The characteristic of a magnet is its demagnetization curve (part of the hysteresis loop lying in quadrant II), shown in Fig. 7.2. Material properties are determined by residual induction values In r and coercive force H With. The useful flux given by the magnet to the external circuit is not constant, but depends on the total effect of external demagnetizing factors.
As can be seen from fig. 7.2, operating point of the magnet outside the motor system N, working point assembled with body M and operating point of the magnet in the motor assembly TO different. Moreover, for most magnetic materials, the process of magnet demagnetization is irreversible, since the return from a point with a lower induction to a point with a higher induction (for example, when disassembling and assembling an electric motor) occurs along return curves that do not coincide with the demagnetization curve.
Due to this important advantage barium oxide magnets used in the automotive industry is not only their relative cheapness, but also the coincidence within certain limits (up to the inflection point) of the return and demagnetization curves. If the effect of external demagnetizing factors is such that the working point of the magnet moves beyond the knee, then return to the point TO is no longer possible and the operating point in the assembled system will already be the point TO 1 with less induction. Therefore, when calculating electric motors with permanent magnets, it is very important right choice volume of the magnet, which provides not only the operating mode of the electric motor, but also the stability of the operating point when exposed to the maximum possible demagnetizing factors.
Electric motors for starting heaters. Starting heaters are used to ensure a reliable start of the internal combustion engine when low temperatures. The purpose of electric motors of this type is to supply air to maintain combustion in gasoline heaters, supply air, fuel and ensure the circulation of liquid in diesel engines.
A feature of the operating mode is that at such temperatures it is necessary to develop a large starting torque and operate for a short time. To ensure these requirements, the electric motors of preheaters are made with series winding and operate in short-term and intermittent modes. Depending on the temperature conditions, electric motors have different switching times: -5...-10 0 С no more than 20 minutes; -10...-25 0 С no more than 30 min; -25...-50 0 С no more than 50 min.
found wide application V starting heaters electric motors ME252 (24V) and 32.3730 (12V) have a rated power of 180 W and a rotation speed of 6500 min -1.
Electric motors for driving ventilation and heating installations. Ventilation and heating installations are designed for heating and ventilation of salons cars, buses, cabins trucks and tractors. Their action is based on the use of engine heat internal combustion, and performance largely depends on the characteristics of the drive. All electric motors for this purpose are long-duty motors operated at an ambient temperature of -40...+70°C. Depending on the layout of the heating and ventilation system on the vehicle, the electric motors have a different direction of rotation. These electric motors are single or two speed, mostly permanent magnet excitation. Two-speed electric motors provide two modes of operation of the heating installation. Partial operation mode (low speed mode, and therefore also inferior performance) is provided by an additional excitation winding.
On fig. 7.3 shows the design of an electric motor with excitation from permanent magnets for heaters. It consists of: 1 and 5 - plain bearing; 2 – permanent magnet; 3 - brush holder; 4 - brush; 6 - collector; 7 - traverse; 8 - cover; 9 - mounting plate; 10 - spring; 11 - anchor; 12 - body. permanent magnets 2 attached to the body 12 springs 10. Lid 8 attached to the body with screws that are screwed into the mounting plates 9, located in the grooves of the body. Bearings are installed in the body and cover 7 And 5 in which the armature shaft rotates 11. All brush holders 3 are on the traverse 7 from insulating material.
The traverse is fixed on the lid 8. brushes 4, through which current is supplied to the collector 6, placed in brush holders 3 box type. Collectors, as well as in electric motors with electromagnetic excitation, are stamped from a copper tape, followed by crimping with plastic or from a pipe with longitudinal grooves on the inner surface.
Covers and housing are made of sheet steel. For windshield washer motors, the cover and housing can be made of plastic.
In addition to heating installations that use the heat of the internal combustion engine, they are used heating installations independent action. In these installations, an electric motor with two shaft outputs drives two fans, one directs cold air to the heat exchanger and then to the heated room, the other supplies air to the combustion chamber.
Heater electric motors used on a number of models of cars and trucks have a rated power of 25...35 W and a rated speed of 2500...3000 min -1 .
Electric motors for driving windshield wipers. The electric motors used to drive the wipers are subject to requirements to ensure a rigid mechanical characteristic, the ability to control the speed of rotation under various loads, and an increased starting torque. This is due to the specifics of the windshield wipers - reliable and high-quality cleaning of the windshield surface in various climatic conditions.
To ensure the necessary rigidity of the mechanical characteristic, motors with permanent magnet excitation, with parallel and mixed excitation are used, and a special gearbox is used to increase the torque and reduce the speed. In some electric motors, the gearbox is designed as component electric motor. In this case, the electric motor is called a gearmotor. Changing the speed of electric motors with electromagnetic excitation is achieved by changing the excitation current in the parallel winding. In electric motors with excitation from permanent magnets, a change in the armature speed is achieved by installing an additional brush and organizing intermittent mode work.
On fig. 7.4 shows a schematic diagram of the SL136 wiper electric drive with a permanent magnet motor. The intermittent operation of the wiper is carried out by turning on the switch 1 in position III. In this case, the anchor chain 4 relay 7 is switched on. The relay has a heating coil 8, which heats the bimetal plate 9. As the bimetal strip heats up, it bends and the contacts 10 open, de-energizing the relay 11, contacts 12 which interrupt the power of the armature circuit of the electric motor. After the plate 9 cool down and close contacts 10, relay 11 will operate and power will be supplied to the motor again. The wiper cycle is repeated 7-19 times per minute.
Mode low speed carried out by turning on the switch 1 in position II. With this power anchored 4 of the electric motor is fed through an additional brush 3, installed at an angle to the main brushes. In this mode, the current passes only through part of the armature winding 4, which causes a decrease in the armature speed and torque. Wiper high speed mode occurs when the switch is set 1 in position I. In this case, the electric motor is powered through the main brushes and the current passes through the entire armature winding. When setting the switch 1 into position IV power is supplied to anchors 4 and 2 windshield wiper and washer motors and their simultaneous operation takes place. After the wiper is turned off (switch position 0), the electric motor remains energized until cam b approaches moving contact 5. At this point, the cam will open the circuit and the engine will stop. Turning off the motor at a strictly defined moment is necessary for laying the wiper blades in their original position. A thermal bimetallic fuse is included in the armature circuit of 4 electric motors 13, which is designed to limit the current in the circuit during overload.
The work of the wiper in drizzling rain or light snow is complicated by the fact that on windshield little moisture gets in. For this reason, friction and wear of the brushes increase, as well as energy consumption for cleaning the glass, which can cause the drive motor to overheat. The frequency of switching on for one or two cycles and switching off manually by the driver is inconvenient and unsafe, since the driver's attention is distracted from driving for a short time.
To organize a short-term inclusion of the wiper, the electric motor control system can be supplemented with an electronic tact controller, which automatically turns off the wiper motor for one or two cycles at certain intervals. The interval between wiper stops can vary within 2...30 s. Most models of wiper motors have a rated power of 12...15 W and a rated speed of 2000...3000 min -1 .
IN modern cars windshield washers became widespread front glass and headlamp cleaners with electric drive. Electric motors of washers and headlight cleaners operate in intermittent mode and are excitated by permanent magnets, have a low rated power (2.5 ... 10 W).
In addition to the listed purposes, electric motors are used to drive various mechanisms: lifting glass doors and partitions, moving seats, driving antennas, etc. To ensure a large starting torque, these electric motors have sequential excitation and are used in short-term and intermittent operating modes.
During operation, electric motors must provide a change in the direction of rotation, i.e., be reversible. To do this, they have two excitation windings, the alternate inclusion of which provides different directions of rotation. Structurally, electric motors for this purpose are made in the same geometric base and are unified in terms of the magnetic system with electric motors of heaters with a power of 25 W.
The electric drive every year finds the increasing application on cars. The requirements for electric motors are constantly increasing, and this is due to the improvement in the quality of various vehicle systems, traffic safety, a decrease in the level of radio interference, toxicity, and an increase in manufacturability. The fulfillment of these requirements led to the transition from electric motors with electromagnetic excitation to electric motors with excitation from permanent magnets. At the same time, the mass of electric motors decreased, and the efficiency increased by about 1.5 times. Their service life reaches 250...300 thousand kilometers.
Electric motors for heating, ventilation and windshield wipers are developed on the basis of four standard sizes of anisotropic magnets. This makes it possible to reduce the number of produced types of electric motors and to unify them.
Another direction is the use of effective radio interference filters in the designs of electric motors. For motors up to 100 W, filters will be unified for each motor base and built-in. For promising electric motors with a power of 100 ... 300 W, filters are being developed using capacitors - through or blocking large containers. If it is impossible to meet the requirements for the level of radio interference due to the built-in filters, the use of remote filters and shielding of electric motors are planned.
In the longer term, it is expected to use non-contact motors direct current. These motors are equipped with static semiconductor switches that replace the mechanical commutator-collector and built-in rotor position sensors. The absence of a brush-collector assembly allows increasing the life of the electric motor up to 5 thousand hours or more, significantly increasing its reliability and reducing the level of radio interference.
Work is underway to create electric motors with limited axial dimensions, which is necessary, for example, to drive a fan internal combustion engine cooling. In this direction, the search is carried out along the path of creating motors with an end collector, which is located together with brushes inside a hollow armature, or with disk armatures made with a stamped or printed winding.
They continue to develop special electric motors, in particular sealed electric motors for preheaters, which is necessary to improve reliability and use on special vehicles.
Trends in the development of various vehicle systems associated with an increase in efficiency, reliability, comfort and traffic safety lead to the fact that the role of electrical equipment, in particular the electric drive of auxiliary systems, is steadily increasing. At present, even on trucks, at least 3-4 electric motors are installed, and on cars - 5 or more, depending on the class.
Electric drive called an electromechanical system consisting of an electric motor (or several electric motors), a transmission mechanism to a working machine and all equipment for controlling an electric motor. The main devices of the car, where the electric drive is used, are heaters and fans of the passenger compartment, starting heaters, glass and headlight cleaners, mechanisms for lifting windows, antennas, moving seats, etc.
The requirements for electric motors installed in a particular vehicle node are determined by the operating modes of this node. When choosing the type of motor, it is necessary to compare the operating conditions of the drive with the features of the mechanical characteristics of various types of electric motors. It is customary to distinguish between natural and artificial mechanical characteristics of the engine. The first corresponds to the nominal conditions for its inclusion, the normal wiring diagram and the absence of any additional elements in the motor circuits. Artificial characteristics are obtained by changing the voltage on the motor, including additional elements in the motor circuit and connecting these circuits according to special schemes.
Structural scheme electronic system suspension control
One of the most promising areas in the development of the electric drive of auxiliary systems of a car is the creation of electric motors with a power of up to 100 W with excitation from
permanent magnets. The use of permanent magnets can significantly improve the technical and economic performance of electric motors: reduce weight, increase overall dimensions, increase efficiency. The advantages include the absence of an excitation winding, which simplifies internal connections and increases the reliability of electric motors. In addition, due to independent excitation, all permanent magnet motors can be reversible.
The principle of operation of electric machines with permanent magnets is similar to the well-known principle of operation of machines with electromagnetic excitation - in an electric motor, the interaction of the armature and stator fields creates a torque. The source of magnetic flux in such electric motors is a permanent magnet. The useful flux given by the magnet to the external circuit is not constant, but depends on the total effect of external demagnetizing factors. The magnetic fluxes of the magnet outside the motor system and in the motor assembly are different. Moreover, for most magnetic materials, the process of magnet demagnetization is irreversible, since the return from a point with a lower induction to a point with a higher induction (for example, when disassembling and assembling an electric motor) occurs along return curves that do not coincide with the demagnetization curve (hysteresis phenomenon). Therefore, when assembling the electric motor, the magnetic flux of the magnet becomes less than it was before disassembling the electric motor.
In this regard, an important advantage of barium oxide magnets used in the automotive industry is not only their relative cheapness, but also the coincidence within certain limits of the return and demagnetization curves. But even in them, with a strong demagnetizing effect, the magnetic flux of the magnet after removing the demagnetizing effects becomes smaller. Therefore, when calculating electric motors with permanent magnets, it is very important to choose the correct volume of the magnet, which ensures not only the operating mode of the electric motor, but also the stability of the operating point when exposed to the maximum possible demagnetizing factors.
Electric motors for starting heaters. Starting heaters are used to ensure reliable start-up of internal combustion engines at low temperatures. The purpose of electric motors of this type is to supply air to maintain combustion in gasoline heaters, supply air, fuel and ensure circulation of liquid in diesel engines.
A feature of the operating mode is that at such temperatures it is necessary to develop a large starting torque and operate for a short time. To ensure these requirements, the electric motors of preheaters are made with series winding and operate in short-term and intermittent modes. Depending on the temperature conditions, electric motors have different switching times: at minus 5 ... minus 10 "C no more than 20 minutes; at minus 10 ... minus 2.5 ° C no more than 30 minutes; at minus 25 ... minus 50 ° C From no more than 50 min.
The rated power of most electric motors in starting preheaters is 180 W, their rotation frequency is 6500 min "1.
Electric motors for driving ventilation and heating installations. Ventilation and heating installations are designed for heating and ventilation of passenger cars, buses, cabs of trucks and tractors. Their action is based on the use of heat from the internal combustion engine, and the performance largely depends on the characteristics of the electric drive. All electric motors for this purpose are long-duty motors operated at an ambient temperature of minus 40 ... + 70 ° С. Depending on the layout of the heating and ventilation systems on the vehicle, the electric motors have a different direction of rotation. These electric motors are single or two speed, mostly permanent magnet excitation. Two-speed electric motors provide two modes of operation of the heating installation. Partial operation mode (mode lower speed, and consequently, lower performance) is provided by an additional excitation winding.
In addition to heating installations that use the heat of an internal combustion engine, heating installations of independent action are used. In these installations, an electric motor with two output shafts drives two fans, one directs cold air into the heat exchanger, and then into the heated room, the other supplies air to the combustion chamber.
Heater electric motors used on a number of models of cars and trucks have a rated power of 25-35 W and a rated speed of 2500-3000 min 1.
Electric motors for driving windshield wipers. The electric motors used to drive the wipers are subject to requirements to ensure a rigid mechanical characteristic, the ability to control the speed of rotation under various loads, and an increased starting torque. This is due to the specifics of the windshield wipers - reliable and high-quality cleaning of the windshield surface in various climatic conditions.
To ensure the necessary rigidity of the mechanical characteristic, motors with permanent magnet excitation, motors with parallel and mixed excitation are used, and a special gearbox is used to increase the torque and reduce the speed. In some electric motors, the gearbox is made as an integral part of the electric motor. In this case, the electric motor is called a gearmotor. Changing the speed of electric motors with electromagnetic excitation is achieved by changing the excitation current in the parallel winding. In electric motors with excitation from permanent magnets, a change in the armature speed is achieved by installing an additional brush.
On fig. 8.2 shows a schematic diagram of the SL136 wiper electric drive with a permanent magnet motor. The intermittent operation of the wiper is carried out by turning on the switch 5A to position III. In this case, the armature circuit 3 of the wiper motor is as follows: "+" of the battery GB - thermobimetallic converter 6 - switch SA(cont. 5, 6) - contacts K1:1 - SA(cont. 1, 2) - anchor - "mass". Parallel anchor through pins K1:1 a sensitive element (heating coil) of an electrothermal relay is connected to the battery KK1. After a certain time, the heating of the sensitive element leads to the opening of the contacts of the electrothermal relay QC1:1. This causes the relay coil to open. K1. This relay is deactivated. His contacts K1:1 open, and the contacts K1:2 become closed. Relay contacts K1:2 and limit switch contacts 80 the electric motor remains connected to the battery until the wiper blades return to their original position. At the moment of laying the brushes, cam 4 opens the contacts 80, causing the motor to stop. The next switching on of the electric motor will occur when the sensitive element of the electrothermal relay KK1 cools down and the relay switches off again. The wiper cycle is repeated 7-19 times per minute. The low speed mode is provided by turning the switch to position I. In this case, the armature 3 of the electric motor is powered through an additional brush 2 installed at an angle to the main brushes. In this mode, the current passes only through part of the armature winding 3. which causes a decrease in the armature speed. Mode high speed wiper occurs when the switch is installed BEHIND to position I. In this case, the electric motor is powered through the main brushes and the current passes through the entire armature winding. When setting the switch BEHIND in position IV, voltage is applied to the armatures 3 and 1 of the electric motors of the wiper and windshield washer and their simultaneous operation occurs.
Rice. 8.2. circuit diagram wiper motor:
1 - washer motor anchor; 2 - additional brush;
3 - armature of the wiper motor; 4 - cam;
5 - time relay; b - thermobimetallic fuse
After switching off the wiper (switch position "ABOUT"-) thanks to the limit switch 50 the electric motor remains on until the brushes are put back in their original position. At this point, cam 4 will open the circuit and the engine will stop. In the armature circuit 3 of the electric motor, a thermal bimetallic fuse 6 is included, which is designed to limit the current strength in the circuit during overload.
The operation of the windshield wiper in drizzling rain or light snow is complicated by the fact that little moisture gets on the windshield. For this reason, friction and wear of the brushes increase, as well as energy consumption for cleaning the glass, which can cause the drive motor to overheat. The frequency of switching on for one or two cycles and switching off manually by the driver are inconvenient and unsafe, since the driver's attention is distracted for a short time from driving. Therefore, to organize a short-term inclusion of the wiper, the electric motor control system is supplemented by an electronic tact controller, which automatically turns off the wiper motor for one or two cycles at certain intervals. The interval between wiper stops can vary between 2-30 seconds. Most models of wiper motors have a rated power of 12-15 W and a rated speed of 2000-3000 min" 1 .
In modern cars, windscreen washers and electric headlight cleaners have become common. The electric motors of the washers and headlight cleaners operate in an intermittent mode and are excitated by permanent magnets, have a low rated power (2.5-10 W).
In addition to the listed purposes, electric motors are used to drive various mechanisms: lifting glass doors and partitions, moving seats, driving antennas, etc. To ensure a large starting torque, these electric motors
In the twenty-first century, it seems that the dream of mankind will come true. Electric cars have not yet displaced hydrocarbon-fuelled vehicles, but better models are slowly emerging. Behind last years many automakers have offered their developments of electric cars to the expert community.
Some went to mass production and managed to win recognition from amateurs and professionals. The top 10 best electric cars of our time include the following models.
Chevy Volt
Enough famous car that uses electric drive is the Chevy Volt. This is not a pure electric car, it has a gas power unit along with an electric motor. The car is intended for movement on city streets. The capacity of the battery allows you to drive 61 km without stopping. Volt REVIEW Chevrolet REVIEW:Chevrolet Spark EV
Not so long ago on automotive market appeared affordable and simple in design electric car Chevrolet Spark EV. The model is produced in two versions: with an electric motor and hybrid version. The cost of this model is 26 thousand dollars. The duration of the trip on the electric drive is limited to 132 km. Chevrolet Spark EV 2016 - Full review:Ford Fusion Energy
Has been on the road for about five years different countries hybrid ford car Fusion Energy. It was the result of close cooperation between the automaker and the developer of electric cars. Lithium-ion batteries are used as power sources and gas cylinders. The battery capacity is enough for a run of only 33 km. Ford Fusion Energy Plug In Hybrid:Ford Focus Electric
The result of the electrification program Ford became Focus car Electric. The car has become an upgrade popular car, which was embedded accumulator battery and a hybrid powertrain. An electric car is great for city driving. On electric traction, the car can travel 121 km. Test drive Ford Focus Elektra:Fiat 500e
A special place among electric cars occupies a novelty from Italy Fiat 500e. The subcompact feels great in the conditions of limited urban space. It is equipped with the latest electric motor, has an elegant appearance. The interior of the car is not only comfortable to drive, but also safe. Fiat 500e test drive Review:Honda Accord Plug-in
Recognized leader among hybrid vehicles power unit is Honda Accord plug-in. It only takes a little drive in this car to experience all the delights of electric vehicles. Honda Accord Plug-In has proven itself not only in megacities, but also on suburban highways. Honda Accord Plug In Hybrid video presentation:Porsche Panamera S Hybrid E
Development hybrid cars engaged and famous Porsche company. Presented to motorists Panamera version S Hybrid E has excellent technical specifications, although the electrical part is considered a weak point in the car. Unlike many electric competitors, the Panamera S Hybrid E has an exceptionally attractive design. Porsche Panamera S e-Hybrid: Green Speed - XCAR:bmw i3
A successful Bavarian development was BMW electric car i3. The car turned out so modern that it resembles a car from fantasy movie. The car has a memorable design, and the mileage is electric drive is 160 km. BMW i3- Big test drive(video version):Tesla Model S
The greatest achievements in the field of manufacturing electric cars has been achieved by Tesla. Model S development is an environmentally friendly sedan model. The cost of an electric car, which reaches 70 thousand dollars, is somewhat scaring off potential buyers. But Tesla Model S can go 426 km without additional battery charging. Tesla Model S - Big test drive (video version):Tesla Model X
Tesla Model X is currently considered the most luxurious electric car. Thanks to innovative developments, the inventor from Tesla Motors managed to get clean car, which is able to overcome 414 km. However, only rich people can purchase this miracle of engineering. There are several modifications that differ in configuration.- Options 70D will cost the buyer 80 thousand dollars. Thanks to a powerful battery (70 kWh), Tesla can travel 345 km.
- Options 90D is estimated at 132 thousand dollars. The car is equipped with a 90 kWh battery, it provides a range of 414 km.
- You can buy a Tesla Model X in the P90D configuration for $140,000. The battery power (90 kWh) is distributed to two axles, providing excellent acceleration dynamics (3.8 s to 96 km/h). Without recharging, the car can cover 402 km.
- the overall battery takes up a lot of space in the car;
- battery properties deteriorate in winter;
- battery life is limited to 2-3 years;
- additional energy is required to heat the passenger compartment.
