Several connection methods and wiring standards for wires

To use electricity, there must be electrical lines and electrical equipment. Where the wires are connected to wires, or where the wires are connected to switches, fuses, fuses, electric lights, motors, household appliances, etc., there must be connectors. After the power is turned on, the current passes through the wires, and the connectors and equipment heat up. If the joint is well done, the contact resistance is not large, and the degree of heat generation is the same as that without the joint, maintaining the normal temperature. If the connection is not good, the wires and wires are not welded tightly. The wires are connected to the terminals of the equipment. Without special joints or tight fastening, the contact resistance at the joints is greatly increased. The heat generated by the current is proportional to the size of the resistor. In the case where the same circuit passes the same amount of current, the greater the resistance, the greater the heat generation, the higher the temperature, and the higher the insulation of the wire. The layer burned out, burning nearby dust and fibers, and igniting nearby combustibles such as wood and clothing. If the joint is loose and the contact is poor, it will generate heat and spark when it is energized. If the joint is not wrapped with insulating cloth, the two joints are close to each other, which will also cause short-circuit of the contact line and spark, and adjacent flammable The substance ignited.

So, how can we connect the wires correctly?

1. The wire insulation can be used to strip the insulation of the wire with wire strippers or wire cutters. The insulation of the plastic hard wire can also be cut with an electric knife.

When the plastic hard wire insulation layer is cut with an electrician knife, the electric knife blade edge is at an angle of 450 to the wire on the wire to be cut, obliquely cut into the insulation layer, and then tilted and tilted at an angle of 250 degrees. Finally, the cut insulation layer is folded and cut into sections. Do not cut the core when cutting the insulation.

2. Straight connection and T-branch connection of single-strand copper conductor

(1) Straight-line connection of single-strand copper conductors Firstly, the two-wire heads are cut into a certain length of core, the oxide layer on the surface of the core is removed, and the two cores are X-shaped and twisted for 2 to 3 turns. Pull the straight line. The straight two-wire head is wound tightly 6 turns on both sides, and the remaining thread ends are cut and the ends of the ends are clamped.

(2) The T-branch connection of the single-strand copper conductor wire intersects the cross-cut core with the trunk core cross, leaving the root of the branch core about 3~5mm, and then winding clockwise on the trunk core. ~ 8 laps, use the wire cutter to cut the remaining core, clamp the end of the core.

Straight line and T-branch connection of 3.7 strands of copper conductor

(1) Straight-line connection of 7-strand copper conductors First, the two-wire end is cut out by about 150 mm and the core of the insulation layer is tightened by about 1/3 of the core, and the linear core is loosened. Clean the surface oxide layer of the core, and then arrange the core into an umbrella shape, and place the two umbrella cores on the forks as shown. Leveling the core, dividing the 7 cores into 2, 2, and 3 sets, and setting the 2 sets of the first core into the state as shown in the figure. After winding 2 times in the clockwise direction, the remaining cores are leveled, and then The second core of the second set is vertical, as shown. Press the second set of cores to hold the remaining cores of the first group and tie the remaining cores tightly by 2 turns, and use the third set of 3 cores to press the core of the residual pressure, as shown, tightly wound 3 turns, cut off The remaining core, the flat end of the clamp, the same method to complete the winding on the other side, complete the straight connection of the 7 strands of wire.

(2) The T-shaped branch of the 7-strand copper conductor is connected to the insulation of the trunk and branch lines. The strand is fastened to the core at 1/8 of the insulation layer, the core of the wire is dissipated, and the surface is straightened and cleaned. . Divide the branch core into 4 and 3 sets, and insert 4 sets into the middle of the trunk core, as shown. The three sets of cores left outside are tightly wound in the clockwise direction on the trunk core for 4 to 5 turns, and the remaining ends of the core clamps are cut off. Then, four sets of cores are tightly wound in the clockwise direction on the other side of the trunk core for 3 to 4 turns, and the remaining cores are cut off, and the flat ends are clamped to complete the T-shaped branch connection.

4.19 copper core conductors are connected in a similar manner to the 7 strand conductors. Because of the large number of core strands, when connecting in a straight line, the middle of the core can be clamped.

After the wires are connected, in order to increase the mechanical strength and improve the electrical conductivity, soldering should also be performed. The method of soldering the copper core wire joint is as follows: firstly, the solder is placed in a tin pot and melted at a high temperature, and the surface-cleaned wire joint is placed on the tin pot, and the molten tin is poured from the joint with a spoon. At the beginning, due to the low temperature at the joint, the joint is not easy to be tinned, and the tin is continuously poured to increase the temperature of the joint, and the tin is soldered until the joint is completely welded. Finally, the surface slag is removed to make the joint surface smooth.

5. The connection of the aluminum core wire is easy to be oxidized due to the aluminum wire, and the resistivity of the oxide film is high, so the aluminum core wire should not be copper.

Aluminum core conductors shall be crimped and crimped. This method is suitable for the connection of small load aluminum core wires. The crimping tube crimping method is connected to a multi-strand aluminum core wire connection for large loads (also applicable to copper core wires), as shown in Figure 3-7. When crimping, select a suitable aluminum crimping pipe according to the specifications of the aluminum core wire. Clean the crimping joint first, and insert the two aluminum core wires into the crimping pipe so that the two wire ends protrude from the crimping pipe by about 30 mm, and then press them with a crimping pliers. When crimping, the first puddle should be pressed against the end of the aluminum core. The crimp quality should meet the technical requirements.

6. Wire insulation recovery

The insulation of the wire must be damaged by external factors or the wire must be restored after it is connected to ensure safe use of electricity. The insulation strength after the insulation is restored should not be lower than the insulation strength of the original insulation layer. Commonly used insulating materials are butter tape, polyester film tape and black tape. When performing insulation recovery, the starting point of the insulating tape should be twice the distance of the insulation from the core. When wrapped, the yellow wax band and the wire should maintain a certain inclination angle, that is, 1/2 of the pressure bandwidth per turn. After wrapping the first layer of yellow wax tape, it is necessary to use a black tape to connect the tail end of the yellow wax tape and then wrap the layer in the opposite direction. The method is the same as before, to ensure the insulation performance after the insulation layer is restored.

Wiring standard:

1. The force of the fastening wire should be moderate. Prevent the bolts and nuts from being buckled when the force is too strong. It is found that the bolts and nuts of the slider have been replaced in time, and it is strictly forbidden to work.

2. When tightening or loosening the screw with a screwdriver, you must force the screwdriver to tighten the screw, and then tighten or loosen it to prevent the screwdriver and the screw from slipping, which makes the screw damage difficult to disassemble, especially in the hanging box.

3, found bolts and nuts that are difficult to disassemble, do not act recklessly, to prevent deformation is more difficult to disassemble, should be given appropriate tapping, or add screw loosening agent, dilute hydrochloric acid, etc. to disassemble later.

4. Do not use a vise to tighten or loosen the bolts and nuts to prevent damage. When using the spanner wrench, adjust the opening to prevent the bolt and nut from being damaged and deformed, resulting in difficulty in disassembly.

5. The same terminal block allows up to two wires of the same type and specification.

6. It is easy to loose or easy to contact poor terminal. The wire connector must be fastened to the terminal block with “?” type to increase the contact area and prevent looseness.

7. When the wire connectors or wire noses are connected to each other, it is strictly forbidden to install non-copper or poorly conductive gaskets in the middle.

8. When the wire joint is connected, the contact surface is required to be smooth and free from oxidation. When the wire nose or copper row is connected, the conductive paste can be applied after the contact surface is cleaned, and then tightened.

9. When connecting the temporary line, the single wire soft wire requires the terminal to be folded once, and then connected to the empty opening; the single-core hard wire should be connected to the empty opening with the “?” type.

10, 30KW and above motor wiring, it is required that the motor cable and the cable connecting the motor are not allowed to cross the gasket with poor conductivity, such as galvanized nut, flat pad, spring pad and so on.

11. When using insulating tape to wrap a cable or other equipment to protect the insulation, the insulation layer should be wound from one end to the other at a ratio of 1/2, and at least one round trip.