Electrical drawing is the core of electrical design, for the later set, PLC program, man-machine interface, equipment installation and operation maintenance are closely related! In the face of a set of electrical drawings, how can we quickly understand the design principle, product selection and wiring mode.
Electrical engineer is the need to make drawings and see two drawing skills, the design of the electrical drawings must be in accordance with the electrical industry standard to design, convenient to maintenance personnel and related personnel engaged in electrical industry to provide help, the more quickly the solution of the electrical fault, convenient maintenance personnel connection at the same time, prevent not connection, look not to understand the drawings, the following together with you to see the electrical drawings, Bring you a real understanding of electrical drawings.
One, get the drawing how to do
1 after obtaining drawings, detailed look at the drawings, the first thing to read carefully the drawings of the main title bar and the relevant specification, such as drawing list, technical specifications, schedule of electrical components, construction specifications, etc., combining with the existing knowledge of electrical, types and characters of the electric diagram, have a clear understanding, understand the drawings from overall situation and to be the focus of the expression.
2. Look at the schematic diagram and block diagram because the schematic diagram and block diagram is only a summary of the basic composition of the system or subsystem, the relationship and its main characteristics, so it is followed by a detailed look at the circuit diagram, in order to understand their working principle. The schematic diagram and block diagram are mostly single-line diagrams, and only some 380/220V low-voltage distribution system schematic diagrams are partially expressed by multi-line diagrams.
3. Reading circuit diagram is the key and difficult point of reading diagram. Circuit diagram is the core of electrical diagram, and it is also the most abundant and difficult electrical drawing to read. Look at the circuit diagram first of all to see what graphic symbols and text symbols, understand the role of each component of the circuit diagram, distinguish the main circuit and auxiliary circuit, AC circuit and DC circuit.
4, in accordance with the first look at the main circuit, and then look at the order of the auxiliary circuit, look at the main circuit, usually from the bottom to the top, that is, from the beginning of the electrical equipment, the control of electrical components, in order to look at the power supply, look at the auxiliary circuit, from top to bottom, from left to right, that is, look at the main power supply first, and then look at the branches, Analyze the working condition of each branch electrical component and its control relation to the main circuit, pay attention to the connection relation between electrical and mechanical mechanism.
5, by looking at the main circuit, to figure out is how to achieve power load, the power cord is why what electrical components to load and through these electrical components, through the auxiliary circuit, should determine the composition of the auxiliary circuit, contact and control relationship between the electrical components and their actions, etc., as well as the interrelation between the understanding of auxiliary circuit and main circuit, Then the whole circuit to understand the working principle and context.
6, circuit diagram and wiring diagram control up to see the wiring diagram and circuit diagram reference to look at the picture, can help to see the wiring diagram, read the wiring diagram according to the terminal marks, loop label from the power supply in order to check, clear line and to the connection method of the circuit, every line figure out is how to through the various electrical components form a closed loop, Board (screen), must open circuit are connected through terminal board, panel with the date line, line terminal board has several contact, an external circuit as long as the number of line on the terminal board with no contact from the can, look at the wiring diagram, the switchboard (screen) inside and outside of the circuit to make clear, we must pay attention to determine the wiring of the terminal board.
Two, look at the electrical control circuit diagram method
The general method of looking at electrical control circuit diagram is to first look at the main circuit, and then look at the auxiliary circuit, and use the circuit of the auxiliary circuit to study the control program of the main circuit.
A: Look at the steps of the main circuit
1, see the main circuit of electrical equipment, electrical equipment refers to the consumption of electricity appliances or electrical equipment, see the diagram first to see clearly there are several electrical appliances, their categories, uses, wiring and some different requirements.
2, to find out what electrical equipment is controlled by electrical components, there are many ways to control electrical equipment, some directly with switch control, some with a variety of starter control, some with contactor control.
3. Understand the control and protection appliances used in the main circuit. The former refers to other control elements besides the conventional contactor, such as power switch (transfer switch and air circuit breaker), universal transfer switch, and the latter refers to short-circuit protection devices and overload protection devices. For example, the specification of the electromagnetic release and thermal overload release in the air circuit breaker, the purpose and specification of the components such as the fuse, thermal relay and overcurrent relay, etc., after the analysis of the main circuit as above, the auxiliary circuit can be analyzed.
4. Look at the power supply. It is necessary to know the voltage level of the power supply, whether it is 380V or 220V, whether it is supplied from the bus busbar or the distribution panel, or whether it is connected from the generator set.
B: Look at the steps of the auxiliary circuit
Auxiliary circuit includes control circuit, signal circuit and the lighting circuit, control circuit is analysed, according to the main circuit of the motor and control requirements of electrical appliances, one by one to find out other control links in the control circuit, control circuit "pieces", according to the function different divided into several local control circuit for analysis, if the control circuit is complex, The lighting, display and other circuits that are not closely related to the control can be excluded first, so as to concentrate on the analysis.
1, the power supply, first to see the kinds of power supply, ac or dc, second, to see the power of the auxiliary circuit is from where to meet, and its voltage grade, general from the main circuit of power supply to two phase line, the voltage is 380 v, also has from the main circuit of a phase line and a zero line, the voltage for the single-phase 220 v, Can also be connected from the special isolation power transformer, voltage 140, 127, 36, 6.3V, etc.
Auxiliary circuit for dc, dc power supply can pick up from the rectifier, generator, or amplifier, the voltage is 24, 12, 6, 4.5, 3 v, etc., all the electrical components of the coil of auxiliary circuit rated voltage must be consistent with the auxiliary circuit power supply voltage, otherwise, the low voltage circuit element is not action, high voltage, will burn out the electrical components coil.
2, understand the use of various relays and contactors used in the control circuit, such as the use of some special structure of the relay, but also understand their principle of action.
3, according to the auxiliary circuit to study the action of the main circuit, analysis of the above content combined with the requirements of the main circuit, can analyze the action process of the auxiliary circuit, the control circuit is always drawn in order of action between two horizontal power lines or two vertical power lines.
So, also can from left to right or from top to down is analyzed, the complex auxiliary circuit, the auxiliary circuit in the circuit form a large loop, in the large loop is divided into several independent small loop, each a small loop control with electric or an action, when a small loop form a closed loop current to flow through, In the circuit of electrical components (contactor or relay) action, the electrical equipment to connect or cut the power supply, in the auxiliary circuit is generally on the button or switch to connect the circuit.
For the analysis of the control circuit must be conducted by combining the action of main circuit requirements at any time, only a comprehensive understanding of the requirements of the main circuit to control circuit, in order to grasp the action principle of control circuit, do not look at the action principle of each part in isolation, but should pay attention to whether there is a mutual restriction relations between each action, such as motor should have interlocking between positive and reverse.
4, the study of the relationship between electrical components, all electrical components in the circuit are not isolated but interrelated, mutual restriction, this mutual control relationship is sometimes shown in a loop, sometimes in several loops.
5. Study other electrical equipment and components, such as rectifying equipment and lighting, etc.
Three, to sum up
The key points of line checking and drawing method of electrical control circuit diagram are as follows:
1. Analyze the main circuit
From the main circuit hand, according to the control requirements of each motor and executive appliances to analyze the control content of each motor and executive appliances, such as motor starting, steering control, braking and other basic control links.
2. Analyze auxiliary circuits
See the auxiliary circuit power supply, make clear the function of each electrical component in the auxiliary circuit and the restriction relationship between each other.
3. Analysis of interlocking and protection
Production machinery has high requirements for safety and reliability. To achieve these requirements, in addition to reasonable selection of drag and control scheme, a series of electrical protection and necessary electrical interlocking are also set up in the control line.
4. Analyze the special control link
In some control circuit, and set up some not close relations with the main circuit, control circuit, relatively independent of specific links, such as product counting device, automatic detection system, thyristor trigger circuit, automatic temperature control device, etc., these parts are often form a small system, the graph analysis method can be reference to the above analysis, And flexible use of the learned electronic technology, communication technology, automatic control system, detection and conversion of knowledge one by one analysis.
5. Overall inspection
After "breaking the whole into pieces", and gradually analyzing the working principle of each local circuit and the control relationship between each part, we must also use the "set zero as the whole" method, check the whole control line, see if there is any omission, and finally from the overall point of view to further check and understand the connection between the control links, To achieve a clear understanding of the circuit diagram of each electrical component of the role, working process and the main parameters.