The introduction course of basic knowledge of electric power needs to know that our life is inseparable from power supply now, and it is precisely because of the existence of power supply that our usual life can become more convenient. Let's learn the basic knowledge of electric power.
Basic knowledge of electric power course 1 1, basic concepts and laws of circuits and analysis of DC resistive circuits.
2, understand the laws and regulations of production safety; Prevent accidents and cause unnecessary casualties.
3. Current knowledge. The harmfulness of current is also considerable, and accidents will happen if you are not careful.
4. Electrical fire prevention, riot prevention, lightning protection and anti-static;
5, lighting equipment and installation
6. Installation of electric wires;
7, understand the high voltage electrical equipment;
8. Safe operation of power transformers, transformers, distribution stations and power supply systems;
9, low-voltage electrical equipment, power capacitors, motors, hand-held power tools;
10, look at the circuit diagram or something.
Beginners of electrical engineering must start with the basic knowledge of electrical engineering. I suggest buying a professional book on electrical engineering first. You can also watch some university electrotechnics teaching videos online. The basic theory is very important, and all kinds of electrical control theories should be understood. It is no problem to master system theory in a year or so.
The key to electrical engineering is practice, guided by theory, and more hands-on. The premise is that you must have a strong interest in electricity, so that you can make rapid progress. At present, electrical automation develops rapidly, and equipment is eliminated and updated quickly. The skills you master today may not be used tomorrow, so you should keep learning. Have a good English foundation, otherwise it will be very inconvenient for you to contact with imported equipment maintenance programming, including the use of various software.
If you are new to the electrician industry, you need to take an electrician's license. The electrician certificate is now an entry certificate for the electrician industry. Anyone who wants to engage in the electrician industry needs an electrician's license. Electrician is a job with very high safety requirements, so holding a certificate is an emphasis on safety.
Learn the basic control principle of secondary loop from scratch;
Starting the motor is not as simple as closing the brake. There is still a lot of work to be done to realize remote control and multipoint control. This paper lists several basic motor control circuits, which are not only necessary for mechanical control in production, but also essential units for designing PLC circuits. This article will explain from easy to difficult one by one. Common component buttons of motor control circuit ▼
Buttons are divided into start button, stop button and mechanical interlock button. The first two have ***4 terminals, and the latter has 6 terminals. The start key is mostly green, and the interior is usually disconnected. Press the button, the interior is closed, and then it is disconnected after being released.
The stop button is mostly red, and the inside is usually closed. When the button is pressed, the interior is disconnected, then released and closed again. The mechanical interlock button can be regarded as a double-throw switch with ***6 terminals. Connect the left terminal at ordinary times, connect the right terminal after pressing it, and restore the left terminal after releasing it. It can be used as a start button or a stop button at will. Buttons are generally represented by SB. If there are multiple buttons at the same time, numbers will be added after SB, such as SB 1, SB2. Contactor/relay ▼
The picture above shows a contactor. The relay is smaller than it, but the principle is the same. * * * There are two rows of *** 12 terminals (two terminals, one in and one out, 1 group). The top row of terminals has two normally closed contacts and 1 coil contacts, and the bottom row has three normally open contacts. Working characteristics: when the coil is not energized, the normally closed contact is closed and the normally open contact is disconnected; After the coil is energized, the normally closed contact is disconnected and the normally open contact is closed.
Contactor, no matter which contact or coil, is denoted by KM. If there are multiple contactors, add a number after KM, such as KM 1, KM2. All contacts and coils of the same contactor use a set of labels, such as normally open contacts, normally closed contacts and coils of contactor KM 1, and the symbol in the circuit diagram is KM 1. Inching and linkage inching: that is, press the button to start the motor, and release the button to stop the motor. Linkage: that is, the motor starts when the button is pressed, and continues to run after it is released. Circuit ▼
In the above picture, the left side is the main loop, and the three pictures A, B and C on the right side are three different control loops. In Figure A, the motor starts when the button SB is pressed, and stops when the button is released. This is a typical inching control. In Figure B, when the circuit breaker SA is turned off, press the button SB2, the contactor coil KM is energized, and the normally open contact KM is closed. However, there is a circuit breaker under the normally open contact KM to disconnect it, so although the motor is started at this time, it will still stop after being released.
After closing the circuit breaker SA, press the button SB2 to energize the contactor coil KM. At this time, the normally open contact KM is closed, so the motor can still run normally after releasing SB2. At this point, the motor is in a linked state. Therefore, this drawing can manually control the inching or linkage state. In Figure C, there is no circuit breaker, but there is a mechanical interlock switch SB3. When the button SB2 is pressed, the contactor coil is energized, the normally open contact KM is closed, and the motor is started. After release, the normally open contact is still closed, so the motor runs normally.
When the button SB3 is pressed, the normally closed contact SB3 below the normally open contact of the contactor is disconnected, and at the same time, the normally open contact of the button SB3 is closed, and the motor is started, and the motor is stopped after being released (at this time, the normally open contact of the contactor is not connected to the circuit). Therefore, this circuit can directly press SB3 when the motors are linked, and it becomes inching. When the motor is linked, after the start button is released, the normally open contact KM is closed because the contactor coil is energized, and the motor can realize continuous operation. This concept is called "self-locking".
Motor inching and linkage are just a concept, and no one wants their motor inching. Here we just need to know how to keep the motor running continuously. Control of motors in different places This paper takes the control of motors in two places as an example. Multi-control motors are generally divided into remote control and local control. That is, put the start button in different button boxes, and then install the button boxes where they need to be controlled.
With the knowledge of inching and linkage, the function of contactor KM in this figure is needless to say. In the figure, SB 1 1 and SB2 1 are stop buttons, while SB 12 and SB22 are start buttons. Any start button and stop button are installed in the same button box, and the other two are also installed in another button box. The two button boxes can be placed beside the control room and the motor respectively. Physical connection diagram ▼
When controlling the motor in different places, it is only necessary to pay attention to all the stop buttons connected in series and all the start buttons connected in parallel. Take the sequential starting of two motors M 1 and M2 as an example. M 1 is required to be started before M2 can be started, and M 1 can be started separately. Circuit ▼
Among them, buttons SB 1 and SB3 are stop buttons to control motors M 1 and M2 respectively; Buttons SB2 and SB4 are start buttons, which control motors M 1 and M2 respectively. For the sake of understanding, I highlighted the control loop of M2 in the circuit diagram, that is, when the control loop of M2 is mentioned below, it refers to the one protruding to the right in the above figure.
Similarly, the function of the contactor will not be described in detail. As shown in the figure, when M 1 is not running, that is, the normally open contact KM 1 is not closed, the control loop of M2 is disconnected at this time, so when the start button SB4 is pressed, M2 does not respond. Only when M 1 works normally and KM 1 is closed, the M2 control loop will be electrified and M2 can be started normally. Physical connection diagram ▼
If multiple motors need to be started at the same time, there are two situations: if other motors need to be started after M 1, the control loop of the motor is connected in parallel with the control loop of M2. If it is necessary to start other motors after M2 is started, the control loop of this motor is connected in series with the control loop of M2. The forward and reverse rotation of the motor realizes the forward and reverse rotation of the motor. The principle adopted is to use two contactors to change the phase sequence of three-phase electricity.
Note the main circuit on the left. The three items of electricity L 1, L2 and L3 arrive at the motor M 1 in left, middle and right order through the contactor KM 1. The sequence from contactor KM2 to motor M 1 is right, middle and left. The change of phase sequence realizes the change of motor running direction. This usage can be used on electric cars or electric tricycles to realize the function of reversing. Now there is a more convenient component called "reverse switch", and the principle is like this.
For the convenience of description, it is assumed that when the SB2 loop is closed, the motor rotates in the forward direction, which is hereinafter referred to as the forward loop where SB2 is located and the reverse loop where SB3 is located. Let's look at the control loop. For the convenience of explanation, we have numbered the numbers in the figure, and each number corresponds to the' component directly above it. Similarly, the influence on the normally open coil KM 1 and KM2 of the contactor will not be repeated. The figure is easy to understand without the normally closed contacts of contactors No.6 and No.9 and the normally closed contacts of mechanical interlocking buttons No.5 and No.8. ..
That is, if you press SB2, the motor will rotate forward; If SB3 is pressed, the motor will reverse. There is a problem here, that is, if you press SB2 and SB3 at the same time or press SB3 when the motor is rotating forward, it will cause a short circuit accident. Therefore, we connected the normally closed contact of the contactor in the circuit. The normally closed contact of KM2 is connected in the forward control loop, and the normally closed contact of KM 1 is connected in the reverse control loop. In this way, when the motor rotates forward, because the coil of the contactor KM 1 is energized, the normally closed contact KM 1 is in the off state, so even if the button SB3 is pressed, there will be no response.
The normally closed contacts of two contactors are interconnected in their respective circuits, so that when one contactor is energized, the other contactor cannot be energized, which is called "interlocking". At this time, we are also faced with a more troublesome thing, that is, when the motor is rotating forward, if it is to reverse, the only way is to press the stop button first, and then press the reverse button, which is very troublesome. For convenience, we use a mechanical interlock button and connect its normally closed contact to the next control loop, that is, the numbers 5 and 8 in the figure.
At this time, when the motor rotates forward, we press SB3, and the normally closed contact No.5 is disconnected, that is, the forward rotation circuit loses power, the coil KM 1 loses power, the normally closed contact KM 1 returns to the closed state, and the coil KM2 is energized, so that the reverse circuit works normally. So you don't have to press the stop button when the motor rotates forward and backward. Physical connection diagram ▼
In practical application, it is often necessary to combine all the above circuits, but as long as you understand the principle of a single diagram, no matter how much knowledge is involved.
Basic knowledge of electric power course 2 Basic knowledge of electric power
First of all, according to the classification of national economic industries, the power industry should include two aspects: power production and power supply.
Power production: thermal power generation, hydropower generation, nuclear power generation and other energy sources.
Power supply: the transmission and distribution of electric energy sold by power grid to users, the power supply activities of power supply bureau, etc.
Simply put, it is the behavior that power plants produce electricity, then buy electricity through the state grid and sell it to users.
As we all know, our "National Power Company" has monopolized all our power industries. After the power system reform in 2002, it was divided into the current "State Grid" and "Southern Power Grid" and several major power generation groups.
In addition, "China Electric Power Construction Group Co., Ltd." and "China Energy Construction Group Co., Ltd." are the results of the separation of the main and auxiliary parts of our power grid. They have all changed from the original auxiliary industry to the main business.
State Grid is now the largest power utility company in the world. As an important state-owned backbone enterprise related to national energy security and the lifeline of national economy, the company takes investment in power grid construction and operation as its core business, which provides a strong power guarantee for economic and social development.
State Grid Corporation of China consists of various functional departments of the company headquarters, five provincial companies and several directly affiliated units. The five clean provinces are: North China, East China, Central China, Northeast China and Northwest China.
Basic knowledge of electric power tutorial 3 What are the basic knowledge of novice electricians?
1, the basic knowledge of electrician, which is the basis of analyzing circuits.
2, low-voltage electrical equipment, understand the key of electrical equipment.
3, electrical components and circuits, familiar with the components and circuits, as well as the cognition of electrical drawings.
4, practical experience, for the verification of the above content.
In fact, the most commonly used and affordable electrician is strong electricity. Weak current electrician needs too much theoretical knowledge, and weak current is mostly integrated, so it is generally not easy to go wrong. Even if there is a problem, the integrated circuit is not easy to repair. Still strong electricity.
Strong current must first understand the working principle and usage of some commonly used switches, fuses, contactors, relays, time relays, thermal relays, etc. And learn how to choose these things according to the line requirements after becoming a master.
6, understand the principle of the motor and simple control, here to learn more about the types and selection of motor. Understand the positive and negative rotation of the motor and the positive and negative rotation control circuit, and then gradually deepen, such as the positive and negative rotation control circuit of the motor, automatic cycle control circuit, multi-control circuit of one machine, star angle step-down start circuit of the motor, and braking circuit of the motor (multiple braking methods).
Extended data:
We should know that people (jobs) engaged in industrial production systems such as power production, electrical manufacturing, electrical maintenance, construction and installation industries are usually called electrical engineers.
Electrotechnics, a discipline, mainly studies strong electricity related to electronics. The training method combining theory with practice will be adopted; Strengthen theoretical knowledge, attach importance to practical training, and combine lessons. Power system operation knowledge, electrical safety technology and operating rules, practical operation, etc.