hg0088com网址

赌球网备用网址hg622.com [Electrician knowledge] The old electrician teaches you how to quickly understand the electrical control circuit diagram!

[Electrician knowledge] The old electrician teaches you how to quickly understand the electrical control circuit diagram!

Source of information: Time: 2020-02-21 02:41:27

Millennium Tongzhou vitality north stream

The general method of looking at the electrical control circuit diagram is to look at the main circuit first, then look at the auxiliary circuit, and use the circuit of the auxiliary circuit to study the control program of the main circuit. The electrical control schematic diagram is generally divided into two parts, the main circuit and the auxiliary circuit. The main circuit is the part where the large current flows in the electrical control circuit, including the electrical components connected from the power supply to the motor. The auxiliary circuit is a circuit other than the main circuit in the control circuit, and the current flowing through it is relatively small.
Electrical control schematic
Analysis of the main circuit:
Regardless of line design or line analysis, start with the main circuit. The function of the main circuit is to ensure the realization of the drag requirements of the machine tool. From the composition of the main circuit, the type and working mode of the motor or the executive appliance, the control requirements and protection requirements such as starting, steering, speed regulation, and braking can be analyzed.
Analysis control circuit:
The control requirements of the main circuit are realized by the control circuit. Using the principles of "turning to zero" and "following the steps", the control circuit is divided into a number of local control lines according to functions, starting from the power supply and the master signal and passing through the logic. Judge, write the control flow, and express the automatic working process of the circuit in a simple and clear way.
Analysis auxiliary circuit:
Auxiliary circuit includes the working status display of the actuator, power supply display, parameter measurement, lighting and fault alarm. This part of the circuit is relatively independent and plays an auxiliary role without affecting the main functions. Many parts of the auxiliary circuit are controlled by the components in the control circuit.
Analysis of interlocking and protection links:
Production machinery has high requirements for safety and reliability. To achieve these requirements, in addition to the reasonable selection of dragging and control schemes, a series of electrical protection and necessary electrical interlocks are set in the control circuit. During the analysis of the electrical control schematic diagram, the electrical interlocking and electrical protection links are an important content and cannot be omitted.
General inspection:
After "turning to zero" and gradually analyzing the working principle of each local circuit and the control relationship between the various parts, you must also use the "set zero to round" method to check the entire control circuit to see if there are any omissions. In particular, it is necessary to further examine and understand the relationship between the various control links from an overall perspective in order to correctly understand the role of each electrical component in the schematic diagram.
Look at the steps of the main circuit
Step 1: See the electrical equipment in the main circuit
Electrical equipment refers to electrical appliances or electrical equipment that consume electrical energy. When looking at the picture, you must first clearly see that there are several electrical appliances, their types, uses, wiring methods, and some different requirements.
Step 2: Find out what electrical components are used to control the electrical equipment
There are many ways to control electrical equipment, some are directly controlled by switches, some are controlled by various starters, and some are controlled by contactors.
Step 3: Know the control and protection appliances used in the main circuit
The former refers to control components other than conventional contactors, such as power switches (transfer switches and air, universal transfer switches. The latter refers to short-circuit protection devices and overload protection devices, such as electromagnetic trips and thermal overload in air circuit breakers The specifications of the trip unit, the uses and specifications of components such as fuses, thermal relays, and overcurrent relays. Generally speaking, after analyzing the main circuit as described above, the auxiliary circuit can be analyzed.
Step 4: Look at the power supply
To understand the power supply voltage level, whether it is 380V or 220V, is it powered from the bus bar or the power distribution screen, or is it connected from the generator set.
2. See the steps of the auxiliary circuit
The auxiliary circuit includes a control circuit, a signal circuit, and a lighting circuit. Analyze the control circuit. According to the control requirements of the motors and actuators in the main circuit, find out the other control links in the control circuit one by one, turn the control circuit to zero, and divide it into several local control circuits for analysis according to different functions. If the control circuit is more complicated, you can exclude the circuits that are not closely related to the control, such as lighting and display, in order to focus on the analysis.
Step 1: Look at the power supply
First look at the type of power supply. AC or DC. Secondly. Look at where the power for the auxiliary circuit is coming from, and its voltage level. The power supply is generally connected from two phase lines of the main circuit, and its voltage is 380V. There are also one phase line and a neutral line of the main circuit, and the voltage is single-phase 220V; In addition, it can also be from a dedicated isolated power supply The transformer is connected, and the voltage is 140, 127, 36, 6.3V, etc. When the auxiliary circuit is DC, the DC power can be connected from the rectifier, generator set or amplifier, and its voltage is generally 24, 12, 6, 4.5, 3V, etc. The coil rated voltage of all electrical components in the auxiliary circuit must be consistent with the auxiliary circuit power supply voltage. Otherwise, the circuit components will not operate when the voltage is low; when the voltage is high, the coils of electrical components will be burned out.
Step 2: Understand the purpose of various relays and contactors used in the control circuit
If some special structured relays are used, they should also understand their operating principles.
Step 3: Study the operation of the main circuit based on the auxiliary circuit
After analyzing the above contents and combining the requirements in the main circuit, the operation process of the auxiliary circuit can be analyzed. The control circuit is always drawn between two horizontal power lines or two vertical power lines in the order of action. Therefore, analysis can be performed from left to right or from top to down. For a complex auxiliary circuit, the entire auxiliary circuit constitutes a large loop in the circuit. In this large loop, it is divided into several independent small circuits, and each small circuit controls an electrical appliance or an action. When a small loop forms a closed loop and a current flows, the electrical components (contactors or relays) in the loop act, connecting people with electrical equipment or removing power. In the auxiliary circuit, the circuit is usually connected by a button or a switch. The analysis of the control circuit must be performed at any time in conjunction with the operation requirements of the main circuit. Only after fully understanding the requirements of the main circuit on the control circuit can the control principle of the control circuit be truly grasped. The operation principle of each part cannot be viewed in isolation. Whether there is a mutually restrictive relationship between the various actions, such as interlocking between the forward and reverse of the motor.
Step 4: Study the interrelationship between electrical components
All electrical components in the circuit do not exist in isolation but are interconnected and restricted. This mutually controlled relationship is sometimes manifested in one circuit, sometimes in several circuits.
Step 5: Research other electrical equipment and components
Such as rectification equipment, lighting, etc.
In summary, the main points of the method of checking the line and drawing of the electrical control circuit diagram are:
(1) Analysis of the main circuit
From the main circuit manpower, according to the control requirements of each electric motor and executive electrical appliances, analyze the control content of each electric motor and executive electrical appliances, such as the basic control links of motor starting, steering control, braking, etc.
(2) Analysis of auxiliary circuits
Look at the power supply of the auxiliary circuit, and clarify the role of each electrical component in the auxiliary circuit and the relationship between them.
(3) Analysis of interlocking and protection links
Production machinery has high requirements for safety and reliability. To achieve these requirements, in addition to the reasonable selection of dragging and control schemes, a series of electrical protection and necessary electrical interlocks are set in the control circuit.
(4) Analysis of special control links
In some control circuits, some special links that are not closely related to the main circuit and the control circuit are relatively independent. Such as product counting device, automatic detection system, thyristor trigger circuit, automatic temperature adjustment device, etc. These parts are often a small system. The method of image analysis can refer to the above analysis process, and use the learned electronic technology, communication technology, automatic control system, detection and conversion to analyze one by one.
(5) General inspection
After reducing to zero, and gradually analyzing the working principle of each local circuit and the control relationship between the various parts, you must use the method of integrating zeros to check the entire control circuit to see if there are any omissions. Finally, we need to further examine and understand the connection between the various control links from an overall perspective, so as to clearly understand the role, working process and main parameters of each electrical component in the circuit diagram.
First know how this equipment is operated, used and working;
Look at the circuit block diagram of this device, make clear the connections, relationships, and interactions between the block diagrams, and use the operation, use, and work of the equipment you understand to understand the analysis block diagrams;
Enter the specific circuit of each block diagram. Find the power supply end of the block diagram, the input and output end of the signal ...
Open the actual circuit of the device, first find the corresponding part of the circuit corresponding to the block diagram, and divide the actual circuit into several parts according to the block diagram;
Enter each part of the circuit, compare the circuit diagram, find the position of the corresponding components, and constantly understand the function, work, and possible failure performance of each major component in the actual circuit;
Finally realize the circuit diagram, the understanding of the actual circuit and fault repair!

Spider pond