Read and check the electric control circuit of the

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Reading and troubleshooting of electrical control circuit of ordinary lathe

the electrical control circuit of machine tool is different due to the type, function and processing technology of machine tool. In addition to various cutting movements and auxiliary movements that need electrical control, there are many electrical control contents such as lighting and cooling, and the electrical control circuit is relatively complex

I. electrical drawing rules

the graphics drawn by using the electrical graphics and text symbols specified in the national standards to express the principle, function, purpose of the electrical control system and the layout, connection and installation relationship between electrical components are called electrical drawings. It mainly includes electrical schematic diagram, electrical wiring diagram and electrical installation diagram

the drawing of electrical drawings must comply with the latest electrical drawing standards issued by the National Bureau of standards. At present, there are mainly gb/gt4728 1996~2000 graphical symbols for electrical diagrams, gb7159 1987 general rules for the formulation of text symbols in electrical technology, gb4026 1992 general rules for the identification and application of alphanumeric systems for terminals and specific wire ends of electrical equipment, and gb/t6988 "Electrical drawings, wiring diagrams and wiring tables", gb/t6988.1~4 2002 "preparation of electrical technical documents", etc. In addition, the relevant standards of mechanical drawing and architectural drawing must be observed

1. Drawing rules of electrical components

Figure 1 is the electrical schematic diagram of cw6132 lathe. The diagram includes the connection relationship between all electrical components, conductive parts and wiring terminals of the machine tool

figure 1cw6132 electrical schematic diagram of lathe

1) schematic state of contact

the schematic state of electrical component contact in the electrical diagram should be drawn according to the non energized state and non stressed state of the appliance

for contactors and electromagnetic relay contacts, draw according to the state when the electromagnetic coil is not energized; For buttons and travel switches, draw according to the state when they are not affected by external forces; Draw the low-voltage circuit breaker and combined switch according to the off state; The thermal relay is drawn according to the non tripping state; The speed relay is drawn according to the state when the motor speed is zero; Accident, standby and alarm switches shall be drawn according to the state when the equipment is in normal operation; The manual switch marked with off and other stable operation positions is drawn according to the state when it is turned to the off position

2) text annotation rules

the text annotation in the electrical diagram follows the nearest annotation rules and the same rules. The so-called proximity rule means that the text symbols of the conductive parts of electrical components should be marked near the graphic symbols; The same rule means that different conductive parts of the same electrical component must adopt the same text annotation symbol (as shown in Figure 1, the coil, main contact and auxiliary contact of AC contactor all adopt the same text annotation symbol km)

the text itself should comply with gb4457 Mechanical drawing documents. Chinese characters adopt long imitation Song typeface, and there are seven kinds of word heights: 20, 14, 10, 7, 5, 3.5, 2.5. The font width is about 2/3 of the word height, while the stroke width of numbers and letters is about 1/10 of the word height

2. Connecting line drawing rules

1) connecting line layout form

vertical layout form

graphical symbols of equipment and electrical components are arranged longitudinally from left to right, connecting lines are arranged vertically, and similar items are horizontally aligned. This layout method is generally used in the electrical schematic diagram of machine tools

horizontal layout form

the graphical symbols of equipment and electrical components are horizontally arranged from top to bottom, the connecting lines are horizontally arranged, and similar items are vertically aligned

the wiring layout used in drawing the electrical schematic diagram should be consistent with the actual wiring layout in the electrical control cabinet

2) on-off of cross node

cross node actively improves the technical advantages of Nd-Fe-B products. Draw a black dot at the point to indicate that the two cross connections are connected at the node, and there is no electrical connection without a black dot; The t-byte point is the on node, as shown in Figure 2

3) wire number and specification marking

Figure 2 on-off of cross node

a) cross node with black dot b) cross node without black dot C) T-shaped node

wire number is marked with L1, L2, L3, u, V, W, etc. the connection specification is marked with outgoing line according to the principle of proximity. For example, outgoing line marking is adopted in Figure 1. 2.5mm2 marked at the end of outgoing line in the main circuit partition of cooling motor indicates that the sectional area of connection is 2.5mm2. Too many wiring specifications will cause confusion in the drawing, which can be marked in the list of electrical components

4) node digital symbol marking

for convenience of annotation, digital symbols can also be marked at each circuit node of the electrical schematic diagram, as shown in Figure 4, 5, 6, 7 and 8 of the lighting circuit area in Figure 1. Numerical symbols are generally arranged according to the flow direction of current in the branch. In addition to the function of annotation, the function of node number symbols also plays the role of corresponding the electrical schematic diagram to the diagram with higher corrosion resistance of electrical wiring

3. Map partition rules

in order to determine the location and purpose of the content on the map, some electrical diagrams with large format and complex content should be partitioned

1) zoning method and its annotation

in the electrical schematic diagram of vertical layout, the upper part is generally divided by text description from left to right according to the main circuit and each functional control link, and the text description is added in the box of each partition to help the reading and understanding of the electrical principle of the machine tool; The lower part is generally marked with numbers from left to right according to the principle of branch centering, and numbers are added in the boxes of each division to facilitate the reference of the contact positions of relays, contactors and other electrical appliances. The principle of branch centering refers to that the vertical line of each branch should be aligned with the central line of the digital partition box. For the electrical schematic diagram with horizontal layout, the left and right partitions are realized. The text description partition is carried out from top to bottom on the left, and the digital annotation partition is carried out from top to bottom on the right

2) contact index code

the AC contactor and relay in the electrical schematic diagram, because the coil, main contact and auxiliary contact play different roles, in order to clearly show the working principle of the electrical schematic diagram of the machine tool, these components are usually drawn in the branches that play their roles. In the complex electrical schematic diagram with large format, in order to facilitate retrieval, it is necessary to mark the contact index code of the electromagnetic coil below the graphic symbol of the electromagnetic coil, as shown in Figure 3

Figure 3 contact index code of electromagnetic coil

a) contactor contact index code B) relay contact index code

for contactor contact index code, it is divided into three columns: the left column number represents the digital partition number where the main contact is located, the middle column number represents the digital partition number where the normally open auxiliary contact is located, and the right column represents the digital partition number where the normally closed auxiliary contact is located

the index code of relay contact is divided into two columns: the left column represents the digital partition number of normally open contact, and the right column represents the digital partition number of normally closed contact

4. The drawing rules of electrical wiring diagram

the electrical diagram that represents the detailed information such as the connection relationship, wiring types and laying routes among various items (including electrical components, components, equipment, etc.) in the electrical control system is called the electrical wiring diagram. The electrical wiring diagram is an indispensable technical document for checking and repairing circuits. According to the different expression objects and uses, it can be divided into unit wiring diagram, interconnection wiring diagram and terminal wiring diagram, etc

Figure 4 is the electrical interconnection line diagram of cw6132 lathe. The graphics and text symbols of the electrical components in the wiring diagram are consistent with the electrical schematic diagram of the cw6132 lathe, but the positions of the electrical components are drawn according to the actual positions of the electrical components in the control cabinet, control panel, console or operation box. In the figure, the dotted line box on the left represents the electrical control cabinet of cw6132 lathe, the small box in the middle represents the lighting control panel, and the small box on the right represents the machine tool motion control panel

figure 4cw6132 lathe electrical interconnection line diagram

all electrical components in the electrical control cabinet can be directly connected, while the connection between external components and the electrical cabinet must be carried out through the wiring terminal board. The connecting wire should indicate the number of wires, cross-sectional area of wires, etc., which generally does not indicate the actual wiring path of wires. During construction, the operator should choose the best wiring method according to the actual situation

II. Electrical control of C650 lathe

Figure 5 is the electrical control schematic diagram of C650 horizontal lathe. There are three motors in the lathe: M1 is the spindle motor, which drives the spindle to rotate and realizes the feed movement through the feed mechanism. The main electrical control requirements are forward rotation and reverse rotation control, rapid stop during parking brake, jog operation during processing adjustment, etc. M2 is the cooling pump motor, which drives the cooling pump motor to supply liquid to the parts processing part. The electrical control requirement is to start the liquid supply during processing and can operate for a long time. M3 is a fast-moving motor, which drives the tool holder to move quickly. It is required to be able to manually control the start and stop at any time

figure 5c650 horizontal lathe electrical control circuit

1 Power circuit

1) main motor circuit

power supply introduction and fault protection

three phase AC power supplies L1, L2 and L3 are introduced into the main circuit of C650 lathe by QS disconnector after passing through fuse Fu. In the main motor circuit, fu1 fuse is a short-circuit protection link, FR1 is a heating element of thermal relay, which plays an overload protection role for motor M1

forward and reverse rotation of main motor

km1 and km2 are the main contacts of AC contactors KM1 and km2 respectively. According to the analysis of basic knowledge of electrical control, when KM1 main contact is closed and km2 main contact is disconnected, three-phase AC power supply will be connected to U1, V1 and W1 three-phase windings of the motor respectively, and M1 main motor will rotate forward. The anti composition industry has deep cooperation with steel processing enterprises for automobile lightweight. When the main contact of KM1 is disconnected and the main contact of km2 is closed, the three-phase AC power supply will be connected to the W1, V1 and U1 three-phase windings of M1 main motor respectively. Compared with the forward rotation, U1 and W1 are replaced, resulting in the reversal of the main motor

full voltage and reduced voltage state of the main motor

when the KM3 main contact is disconnected, the three-phase AC power supply current will flow through the current limiting resistance R and enter the motor winding, and the motor winding voltage will be reduced. If the KM3 main contact is closed, the power supply current is directly connected to the motor winding without current limiting resistance, and the main motor is in full voltage operation state

winding current monitoring

ammeter a plays the role of winding current monitoring in the main circuit of motor M1. It is sleeved on the wiring of one phase of winding through TA coil. When there is current flowing through the wiring, induced current will be generated, and the current current value in motor winding will be displayed through this induced current. The control principle is that when the KT normally closed delayed opening contact is closed, the induced current generated by TA does not pass through the a ammeter, and once the KT contact is disconnected, the a ammeter can detect the current in the motor winding

motor speed monitoring

ks is a speed relay detection element installed in the same rotation with the main shaft of M1 main motor, which controls the closing and opening of the speed relay contact according to the main shaft speed of the main motor

2) cooling pump motor circuit

in the cooling pump motor circuit, fu4 fuse plays the role of short-circuit protection, and FR2 thermal relay plays the role of overload protection. When the km4 main contact is disconnected, the cooling pump motor M2 stops running without liquid supply; Once the km4 main contact is closed, M2 will start to supply liquid

3) fast moving motor circuit

Fu5 fuse in fast moving motor circuit plays the role of short-circuit protection. When the km5 main contact is closed, the fast-moving motor m3 starts, and when the km5 main contact is disconnected, the fast-moving motor m3 stops

the main circuit establishes electrical connection with the control circuit and lighting circuit through TC transformer. The access voltage at the primary side of TC transformer is 380V, and there are 36V and 110V power supplies at the secondary side, of which 36V supplies power to the lighting circuit and 110V supplies power to the lathe control circuit