Mechanization and automation. Types of automatic devices.
Basic concepts of TAU
In any process performed by a person, two types of operations can be distinguished:
1. work operations;
2. monitoring and control operations.
Work operations necessary for the direct implementation of a technical process, for example, removing chips, rotating the machine shaft. Work activities are associated with costs physical energy. Replacing human labor in work operations is called mechanization.
Control operations are associated with the measurement of physical quantities, and control operations designed for correct and high-quality management of the process and aimed at its improvement. Replacing human labor in operations to monitor and manage the operation of instruments and devices is called automation.
A set of technical devices that perform a given process and are subject to automation. called control object(OU).
Technical devices, performing control operations are called automatic.
The set of automatic devices and control objects forms control system(SU). A system in which all work and control operations are performed automatically, without human intervention, is called automatic. A system in which only part of the control operations are performed automatically, and the other part is performed by people, is called automated.
When automating production processes Depending on the use of means and methods, both simpler and more complex influences on the process are possible. By purpose, the following types of automatic devices can be distinguished.
1. System automatic control(SAK).
2. Automatic protection and blocking system (SAZ and B).
3. Automatic counting and solving devices (ACD).
4. Systems automatic regulation(SAR).
5. Automated control systems (ACS).
1. NAC are designed to measure controlled physical quantity and its registration without human participation. It includes a sensor, a recording device (indicating or recording) and an alarm device.
2. The SAZ serves to prevent damage to equipment when abnormal operating conditions occur. Automatic locking serves to prevent personnel errors.
3. Automatic decision devices include control computers that perform various calculations and determine the optimal operating mode.
4. Automatic regulation is called maintaining a constant or variable according to a given law of some output quantity. ATS is special case Self-propelled guns.
5. The ACS carries out a complex set of impacts on the object, changing the parameter of the controlled technical process in accordance with the change in the controlled physical quantity. In addition, the tasks of the self-propelled guns include:
· implementation of extreme regulation;
· optimal control, i.e. finding optimal modes for solving certain problems;
· adaptation or self-tuning of an automatic device.
Thus, we can say that the subject of TAU studies:
1. Principles of construction of automatic control systems and self-propelled guns.
2. Determination of the mathematical description of these systems in the form differential equations(DE) and transfer functions.
3. Research and analysis of the stability of these systems.
4. Analysis of the accuracy of control processes in steady state.
5. Synthesis of ACS and ACS. Includes defining the control algorithm, i.e. regulatory law, in accordance with which automatic device must influence the object in the event of a change in the controlled variable.
Circuit breakers are devices that provide protection for wiring in short circuit, when connecting a load with indicators exceeding the established values. They should be selected from special attention. It's important to consider the types circuit breakers, their parameters.
Vending machines of different types
Characteristics of machines
When choosing a circuit breaker, it makes sense to focus on the characteristics of the device. This is an indicator by which you can determine the sensitivity of the device to possible excess current values. Different types circuit breakers have their own marking - it is easy to understand how quickly the equipment will respond to excess current values to the network. Some switches respond instantly, while others activate over a period of time.
- A is a marking that is affixed to the most sensitive equipment models. Automatic machines of this type immediately register the fact of overload and promptly respond to it. They are used to protect equipment characterized by high accuracy, but it’s almost impossible to meet them in everyday life
- B is a characteristic possessed by switches that operate with an insignificant delay. In everyday life, switches with the appropriate characteristics are used together with computers, modern LCD TVs and other expensive household appliances
- C is a characteristic of machines that are most widely used in everyday life. The equipment begins to function with a slight delay, which is sufficient for a delayed response to registered network overloads. The network is switched off by the device only if it has a fault that really matters
- D - characteristic of switches with minimal sensitivity to excess current. Basically, such devices are used to supply electricity to a building. They are installed in panels and control almost all networks. Such devices are chosen as a backup option, since they are activated only if the machine does not turn on in time.
All parameters of circuit breakers are written on the front part
Important! Experts believe that the ideal performance of circuit breakers should vary within certain limits. Maximum - 4.5 kA. Only in this case the contacts will be under reliable protection, and current discharges will be discharged under any conditions, even if the established values are exceeded.
Types of machines
The classification of circuit breakers is based on their types and features. As for types, we can highlight the following:
- Rated breaking capacity - we are talking about the resistance of the switch contacts to the effects of high currents, as well as to conditions in which deformation of the circuit occurs. Under such conditions, the risk of burning increases, which is neutralized by the appearance of an arc and an increase in temperature. The higher quality and durable the equipment is made of, the higher its corresponding capabilities are. Such switches are more expensive, but their characteristics fully justify the price. Switches last a long time and do not require regular replacement
- Rating calibration - we are talking about the parameters in which the equipment operates in normal mode. They are installed at the production stage of the equipment, and are not regulated during its use. This characteristic allows you to understand how strong overloads the device can withstand, the period of time it operates in such conditions
- Setpoint - usually this indicator is displayed as a marking on the equipment body. It's about about the maximum current values in non-standard conditions, which, even if switched off frequently, will not have any effect on the functioning of the device. The setting is expressed in current units, marked in Latin letters and digital values. Figures, in in this case, display the denomination. Letters can be seen in the markings of only those machines that are manufactured in accordance with DIN standards
Circuit breakers are devices that are responsible for protecting an electrical circuit from damage caused by exposure to large currents. Too much electron flow can damage household appliances, and also cause overheating of the cable with subsequent melting and fire of the insulation. If you do not de-energize the line in time, this can lead to a fire. Therefore, in accordance with the requirements of the PUE (Electrical Installation Rules), operation of a network in which electrical circuit breakers are not installed is prohibited. AVs have several parameters, one of which is the time-current characteristic of the automatic protective switch. In this article we will tell you how circuit breakers of categories A, B, C, D differ and what networks they are used to protect.
Features of operation of network protection circuit breakers
Whatever class the circuit breaker belongs to, its main task is always the same - to quickly detect the occurrence of excessive current and de-energize the network before the cable and devices connected to the line are damaged.
Currents that may pose a danger to the network are divided into two types:
- Overload currents. Their appearance most often occurs due to the inclusion of devices in the network, the total power of which exceeds what the line can withstand. Another cause of overload is a malfunction of one or more devices.
- Overcurrents caused by short circuit. A short circuit occurs when the phase and neutral conductors are connected to each other. In normal condition they are connected to the load separately.
The design and principle of operation of the circuit breaker is on video:
Overload currents
Their value most often slightly exceeds the rating of the machine, so the passage of such an electric current through the circuit, if it does not drag on for too long, does not cause damage to the line. In this case, instantaneous de-energization is not required in this case; moreover, the electron flow often quickly returns to normal. Each AV is designed for a certain excess of electric current at which it is triggered.
The response time of the protective circuit breaker depends on the magnitude of the overload: if the norm is slightly exceeded, it can take an hour or more, and if it is significant, it can take several seconds.
A thermal release, the basis of which is a bimetallic plate, is responsible for turning off the power under the influence of a powerful load.
This element heats up under the influence of a powerful current, becomes plastic, bends and triggers the machine.
Short circuit currents
The flow of electrons caused by a short circuit significantly exceeds the rating of the protective device, causing the latter to immediately trip, cutting off the power. An electromagnetic release, which is a solenoid with a core, is responsible for detecting a short circuit and immediate response of the device. The latter, under the influence of overcurrent, instantly affects the circuit breaker, causing it to trip. This process takes a split second.
However, there is one caveat. Sometimes the overload current can also be very large, but not caused by a short circuit. How is the device supposed to determine the difference between them?
In the video about the selectivity of circuit breakers:
Here we smoothly move on to the main issue that our material is devoted to. There are, as we have already said, several classes of AB, differing in time-current characteristics. The most common of them, which are used in household electrical networks, are devices of classes B, C and D. Circuit breakers belonging to category A are much less common. They are the most sensitive and are used to protect high-precision devices.
These devices differ from each other in terms of instantaneous tripping current. Its value is determined by the multiple of the current passing through the circuit to the rating of the machine.
Trip characteristics of protective circuit breakers
Class AB, determined by this parameter, is indicated by a Latin letter and is marked on the body of the machine before the number corresponding to the rated current.
In accordance with the classification established by the PUE, circuit breakers are divided into several categories.
MA type machines
A distinctive feature of such devices is the absence of a thermal release. Devices of this class are installed in circuits connecting electric motors and other powerful units.
Protection against overloads in such lines is provided by an overcurrent relay; a circuit breaker only protects the network from damage as a result of short-circuit overcurrents.
Class A devices
Type A machines, as was said, have the highest sensitivity. The thermal release in devices with time-current characteristic A most often trips when the current exceeds the nominal value AB by 30%.
The electromagnetic trip coil de-energizes the network for approximately 0.05 seconds if the electric current in the circuit exceeds the rated current by 100%. If for any reason, after doubling the electron flow, the electromagnetic solenoid does not work, the bimetallic release turns off the power within 20 - 30 seconds.
Automatic machines with time-current characteristic A are connected to lines during operation of which even short-term overloads are unacceptable. These include circuits with semiconductor elements included in them.
Class B protective devices
Devices of category B are less sensitive than those of type A. The electromagnetic release in them is triggered when the rated current is exceeded by 200%, and the response time is 0.015 seconds. Triggering of a bimetallic plate in a breaker with characteristic B at a similar excess of the AB rating takes 4-5 seconds.
Equipment of this type is intended for installation in lines that include sockets, lighting fixtures and other circuits where there is no starting increase in electric current or is of minimal value.
Category C machines
Type C devices are the most common in household networks. Their overload capacity is even higher than those previously described. In order for the electromagnetic release solenoid installed in such a device to operate, it is necessary that the flow of electrons passing through it exceeds the nominal value by 5 times. The thermal release is activated in 1.5 seconds when the rating of the protection device is exceeded five times.
Installation of circuit breakers with time-current characteristic C, as we said, is usually carried out in household networks. They do an excellent job as input devices to protect the general network, while for individual branches to which groups of sockets and lighting, category B devices are well suited.
This will make it possible to maintain the selectivity of the circuit breakers (selectivity), and during a short circuit in one of the branches the entire house will not be de-energized.
Circuit breakers category D
These devices have the highest overload capacity. To trigger the electromagnetic coil installed in a device of this type, it is necessary that the electric current rating of the circuit breaker be exceeded by at least 10 times.
In this case, the thermal release is activated after 0.4 seconds.
Devices with characteristic D are most often used in general networks of buildings and structures, where they play a backup role. They are triggered if there is no timely power outage by circuit breakers in separate rooms. They are also installed in circuits with large starting currents, to which, for example, electric motors are connected.
Protective devices categories K and Z
These types of machines are much less common than those described above. Type K devices have a large variation in the current required for electromagnetic tripping. Yes, for the chain alternating current this indicator should exceed the nominal by 12 times, and for a constant one - by 18. The electromagnetic solenoid is activated in no more than 0.02 seconds. Triggering of the thermal release in such equipment can occur when the rated current is exceeded by only 5%.
These features determine the use of type K devices in circuits with exclusively inductive loads.
Devices of type Z also have different actuation currents of the electromagnetic tripping solenoid, but the spread is not as great as in AB category K. In AC circuits, to turn them off, the current rating must be exceeded three times, and in DC networks, the value of the electric current must be in 4.5 times more than nominal.
Devices with Z characteristic are used only in lines to which electronic devices are connected.
Conclusion
In this article, we looked at the time-current characteristics of protective circuit breakers, the classification of these devices in accordance with the Electrical Regulations, and also figured out in which circuits devices of various categories are installed. The information obtained will help you determine what security equipment should be used on your network based on what devices are connected to it.
Electricity is a very useful and at the same time dangerous invention. In addition to the direct impact of current on a person, there is also a high probability of fire if the electrical wiring is not properly connected. This is explained by the fact that electric current passing through a conductor heats it, and especially high temperatures occur in places with poor contact or during a short circuit. To prevent such situations, automatic machines are used.
What's happened
These are specially designed devices whose main task is to protect wiring from melting. In general, machine guns will not save you from defeat electric shock and will not protect the equipment. They are designed to prevent overheating.
The method of their operation is based on opening the electrical circuit in several cases:
- short circuit;
- exceeding the current flowing through a conductor not intended for this purpose.
As a rule, the machine is installed at the input, that is, it protects the section of the circuit that follows it. Since for breeding to various types devices use different wiring, which means that protection devices must be able to operate at different currents.
At first glance, it may seem that it is enough to simply install the most powerful machine and there will be no problems. However, it is not. A high current that does not work can overheat the wiring and, as a result, cause a fire.
Installation of machines low power will break the circuit every time as soon as two or more powerful consumers are connected to the network.
What does the machine consist of?
A typical machine consists of the following elements:
- Cocking handle. Using it, you can turn on the machine after it has been triggered or turn it off to de-energize the circuit.
- Switching mechanism.
- Contacts. Provide connection and breaking of the circuit.
- Terminals. Connect to a protected network.
- A condition-triggered mechanism. For example, a bimetallic thermal plate.
- Many models may have an adjusting screw to adjust the nominal current value.
- Arc extinguishing mechanism. Present at each pole of the device. It is a small chamber in which copper-plated plates are placed. On them the arc is extinguished and comes to naught.
Depending on the manufacturer, model and purpose, machines can be equipped with additional mechanisms and devices.
Trip mechanism design
The machines have an element that breaks the electrical circuit at critical current values. Their operating principle can be based on different technologies:
- Electromagnetic devices. They are characterized by a high speed of response to a short circuit. When currents of unacceptable magnitude are applied, the coil with the core is activated, which, in turn, turns off the circuit.
- Thermal. The main element of such a mechanism is a bimetallic plate, which begins to deform under the load of high currents. By bending, it has a physical effect on the element that breaks the chain. It works roughly the same way Electric kettle, which can turn itself off when the water in it boils.
- There are also semiconductor circuit breaking systems. But they are used extremely rarely in household networks.
by current values
The devices differ in the nature of their response to an excessively high current value. There are 3 most popular types of machines - B, C, D. Each letter indicates the sensitivity coefficient of the device. For example, a type D machine has a value from 10 to 20 xln. What does it mean? It’s very simple - to understand the range at which the machine is capable of operating, you need to multiply the number next to the letter by the value. That is, a device marked D30 will turn off at 30*10...30*20 or from 300 A to 600 A. But such machines are used mainly in places with consumers that have high starting currents, for example, electric motors.
Type B machine has a value from 3 to 5 xln. Therefore, marking B16 means operation at currents from 48 to 80A.
But the most common type of machine is S. It is used in almost every home. Its characteristics are from 5 to 10 xln.
Legend
Different types of machines are marked in their own way for quick identification and selection of the one needed for a specific circuit or its section. As a rule, all manufacturers adhere to one mechanism, which allows them to unify products for many industries and regions. Let’s take a closer look at the signs and numbers printed on the machine:
- Brand. Usually the manufacturer's logo is placed at the top of the machine. Almost all of them are stylized in a certain way and have their own corporate color, so choosing a product from your favorite company will not be difficult.
- Indicator window. Shows the current status of contacts. If a malfunction occurs in the machine, then it can be used to determine whether there is voltage in the network.
- Machine type. As already described above, it means a shutdown characteristic at currents significantly exceeding the rated current. C is used more often in everyday life and B is used a little less frequently. The differences between the types of electric machines B and C are not so significant;
- Rated current. Shows the current value that can withstand a long-term load.
- Rated voltage. Very often this indicator has two meanings, written separated by a slash. The first is for a single-phase network, the second is for a three-phase network. As a rule, in Russia a voltage of 220 V is used.
- Switch-off current limit. It means the maximum permissible short circuit current at which the machine will turn off without failure.
- Current limiting class. Expressed in one digit or absent altogether. In the latter case, the class number is considered to be 1. This characteristic means the time for which the short circuit current is limited.
- Scheme. On the machine you can even find a diagram for connecting contacts with their designations. It is almost always located in the upper right part.
Thus, by looking at the front of the machine, you can immediately determine what type of current it is intended for and what it is capable of.
Which to choose?
When choosing a protective device, one of the main characteristics is the rated current. To do this, you need to determine what current strength is required by the totality of all consumer devices in the house.
And since electricity flows through wires, the current required for heating depends on its cross-section.
The presence of poles also plays an important role. The most commonly used practice is:
- One pole. Circuits with lighting devices and sockets to which simple devices will be connected.
- Two poles. Used to protect wiring connected to electric stoves, washing machines, heating devices, water heaters. It can also be installed as protection between the shield and the room.
- Three poles. Used primarily in three-phase circuits. This is relevant for industrial or near-industrial premises. Small workshops, production and the like.
The tactics for installing machine guns proceed from larger to smaller. That is, first it is mounted, for example, double-pole, then single-pole. Next come devices with power that decreases at each step.
- When choosing, you should focus not on electrical appliances, but on the wiring, since this is what the circuit breakers will protect. If it is old, it is recommended to replace it so that you can get the most out of it. best option machine.
- For premises such as a garage, or during the event repair work It’s worth choosing a machine with a higher rated current, since different machines or welders have quite high current ratings.
- It makes sense to complete the entire set of protective mechanisms from the same manufacturer. This will help avoid mismatches in current ratings between devices.
- It is better to purchase machines in specialized stores. This way you can avoid buying low-quality fake, which can lead to disastrous consequences.
Conclusion
No matter how simple it may seem to wire a circuit around a room, you should always remember about safety. The use of automatic machines greatly helps to avoid overheating and, as a consequence, fire.
Wherein for a long time The automatic transmission was installed on cars of the middle class and premium segment, but later the unit became widespread.
Due to its enormous popularity, as well as taking into account the constant tightening of regulations and standards regarding fuel efficiency and environmental friendliness, manufacturers are constantly improving automatic transmissions, offering innovative solutions etc.
As a result, today we can distinguish at least three main types of “automatic machines”, which differ greatly from each other in design and operating principles, but each of them is called an automatic transmission. Next we will talk about what types of automatic transmissions there are, as well as what features this or that unit has.
If we talk about the advantages, the hydraulic automatic has a fairly long service life (in some cases up to 500 thousand km), and also provides a good level of driving comfort.
As for the main disadvantages, such a gearbox is expensive to repair, requires regular maintenance, is demanding on the quality of gear oil, is susceptible to prolonged loads and difficult operating conditions, and is not highly economical. We also note that losses in gas turbine engines lead to the fact that the efficiency of hydromechanical automatic machines decreases compared to analogues. As a result, acceleration dynamics suffer.
- (variable transmission CVT) is a separate type of automatic transmission, which for a number of reasons is not as widespread as a hydromechanical automatic transmission.
This transmission, like an automatic transmission, has a torque converter to transmit torque from the internal combustion engine, but the box itself is very different. In short, there are two pulleys mounted on the variator shafts. These pulleys are connected to each other by a belt or chain. Depending on the load and speed, the driving and driven pulleys change their diameter, as a result of which the torque on the wheels also changes. And this happens extremely smoothly.
Taking into account the fact that there are no usual fixed speeds (steps), thanks to this feature, the CVT gearbox is called a continuously variable transmission (flexible change in gear ratio). This type of automatic transmission differs from its analogues in its maximum smoothness, since there is virtually no gear change. Engine speed is also kept at the same level, without a sharp increase or decrease.
As in the case of automatic transmissions, additional modes can be implemented (winter, economical, sports, as well as Tiptronic with imitation of manual gear shifting). When driving a car with a CVT, drivers note the complete absence of noticeable shocks, vibrations, etc. It is also worth highlighting good acceleration dynamics and fuel efficiency.
However, there are also disadvantages. First of all, it does not have a long service life, is extremely complex and expensive to repair, and is demanding on the quality and level of oil. This means that such a box is not installed in conjunction with powerful engines; it is highly not recommended to load the transmission during operation.
- (robot box or robot automatic transmission) is another type of automatic transmission, which, for a number of reasons, became truly widespread about 20 years ago.
It is noteworthy that this unit was developed a long time ago and is actually a manual gearbox with one clutch, in which the operation of the clutch is automated, as well as the selection and on/off of the desired gear.
In simple words, Automatic transmission robot is automated (robotic) mechanics. Such a gearbox is characterized by low production costs (which significantly reduces the cost of the entire car), allows for significant fuel savings (similar to mechanics), as well as dynamic acceleration.
If we consider the disadvantages, then, first of all, we should highlight a noticeable decrease in comfort compared to automatic transmissions and CVTs. In simple words, the clutch remains exactly the same as on a manual transmission, but the robot does not always select the desired gear in a timely manner, quickly and accurately, cannot operate the clutch smoothly, etc.
As a result, at the moment of switching, shocks, jerks, etc. are felt, the robot delays gear changes and does not always accurately select gears in accordance with the constantly changing conditions while driving.
Also, actuators (servomechanisms, actuators) on robotic manual transmissions quickly fail, high-quality repairs is often impossible, that is, it is necessary complete replacement. It is important to understand that such mechanisms are quite expensive.
- (for example, DSG or Powershift) can be considered a more technologically advanced and advanced version of a conventional box - a robot. At the same time, units of this type are devoid of many of the disadvantages of their predecessors.
On the one hand, the design remained similar to the mechanics, but the engineers conventionally placed two such mechanical boxes in one housing. One box has even gears, the other odd, and each has a separate clutch.
In short, while the car is moving, for example, in one gear, the next one after it is also already selected and engaged, but is not engaged, since the clutch is disengaged. At the moment of gear shifting, the working clutch is quickly disengaged, then the second one is instantly engaged. The gear change occurs so quickly that the driver almost does not feel it.
At the same time, the control of such a robot is more reminiscent of the control circuit of an automatic transmission (there is a hydraulic unit called Mechatronic, it is necessary large quantity transmission oil, etc.). At the same time, there is also a large number of servomechanisms (similar to a single-disk robot that has one clutch).
The advantages include high fuel efficiency and excellent acceleration dynamics, high level comfort as well as best ability boxes to cope with high loads compared to automatic transmissions and CVTs.
At the same time, the preselective gearbox is complex and expensive to manufacture, has a noticeably shorter service life, and in practice requires intervention earlier than an automatic transmission or a variator. As for repairs, robots of this type only require qualified maintenance; they often also require sets of expensive special equipment to carry out many procedures (for example,).
How to distinguish a robot from an automatic or CVT
The fact is that manufacturers strive to simplify as much as possible the entire process of interaction between the driver and the gearbox. For this reason, for example, a robot may have the same selector and modes (P-R-N-D) as a CVT or automatic transmission.
As for the driving sensations (provided that the transmission and the car itself are in full working order), you can pay attention to the following:
- AT - often means hydromechanical automatic;
- CVT - variable speed transmission;
- AMT - robotic gearbox with one clutch;
You can also ask a question on specialized auto forums, study technical literature separately, etc.
Let's sum it up
As you can see, each automatic transmission has both strong and weak sides. Also, taking into account the diversity, you may encounter the fact that it can be difficult to immediately determine which automatic transmission is installed on a particular car.
Finally, we note that during operation it is important to separately take into account certain features of a particular machine, depending on the type of transmission and type of automatic transmission. It is also necessary to strictly follow the rules for servicing the automatic transmission, which allows you to increase the resource of the unit.
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