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Electrical Wiring Specification
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Electrical Wiring Specification

Views:155     Author:Site Editor     Publish Time: 2020-12-18      Origin:Site

1. Component installation

1.1 Prerequisite: All components should be installed according to the installation conditions specified by the manufacturer.

Applicable conditions: required arc extinguishing distance.

The space required to remove the arc chute, etc., for the installation of a manual switch, it must be ensured that the arc of the switch does not cause danger to the operator.

1.2 Before assembling, first read the drawings and technical requirements.

1.3 Check whether the product model, component model, specification, quantity, etc. are consistent with the drawings

1.4 Check whether the components are damaged

1.5 Must be installed according to the picture (if there is a picture)

1.6 The assembly sequence of components should be viewed from the front of the board, from left to right, from top to bottom

1.7 The same type of product should ensure assembly consistency

1.8 The height of the centerline of the components on the panel and door shall meet the requirements.

 Component name

 Installation height (m)

 Indicating instrument, indicator light

 0.6 - 2.0

 Electric energy meter

 0.6 - 1.8

 Control switch, button

 0.6 - 2.0

 Emergency operation parts

 0.8 - 1.6

The assembled product should meet the following conditions:

1) Easy to operate. When the components are in operation, they should not be hindered by space, and there should be no possibility of touching live objects.

2) Easy maintenance. It is easier to replace components and maintain connections.

3) The electrical clearances and creepage distances of various electrical components and devices should meet the requirements of Article 4.4.

4) Ensure the installation distance of the primary and secondary lines.

1.9  The fasteners and metal parts used in the assembly should have a protective layer. The burrs and sharp edges of the screw holes, edges, and surfaces should be polished and then coated with conductive paste.

1.10  Appropriate tools should be selected for bolt fastening, and the protective layer of fasteners should not be damaged, and the corresponding torque should be paid attention to.

1. 11 The components on the main circuit, general reactors, and transformers need to be grounded, and circuit breakers need not be grounded. The following figure shows the reactor grounding.



1.12 For the installation of heating elements (such as tube-shaped resistors, heat sinks, etc.), the heat dissipation should be considered, and the installation distance should meet the requirements of the elements. Tubular resistors with a rated power of 75W and above should be installed horizontally, not vertically to the ground. The following picture shows the wrong connection.



1. 13 All electrical components and accessories should be fixedly installed on the bracket or bottom plate, and should not be suspended from electrical appliances and cables.

1.14 There is a label near each component on the wiring surface, and the label should be consistent with the drawing. Except for the signboard attached to the component itself, the signboard shall not be fixed on the component body.

a) Identification of the terminal



1.15 The label should be complete, clear, and firm. The labeling position should be clear and eye-catching.

b) Double sign



1.16 The label of the components installed on the panel and door should be pasted under the components on the back of the panel and door. If there is no position below, it can be pasted on the left, but the pasting position should be as consistent as possible.

c) Devices on the door



1. 17 Protective earthing continuity

The continuity of protective grounding is guaranteed by effective wiring.

When any two metal parts in the cabinet are connected by screws, if there is an insulating layer, the grounding washer of the corresponding specification should be used, and the tooth surface of the washer should be contacted with the surface of the part (red circle), or the insulating layer should be damaged.




The grounding place (red circle) at the door should be "grab pad". Prevent bad contact due to paint problems. And the connection line should be as short as possible.



1.18 When installing components that are easily damaged by vibration, rubber pads should be installed between the components and the mounting plate to absorb vibration.

1.19 For components with operating handles, they should be adjusted in place without jamming.




1. 20  Tighten the bolts reserved for customer wiring on the busbars and components.


2 . Secondary circuit wiring

2.1  Basic requirements: construct according to the drawing and connect correctly.

2.2  The connection of the secondary line (including bolt connection, plug-in connection, welding, etc.) should be firm and reliable, the wiring harness should be horizontal and vertical, the configuration should be firm, the layers should be clear, neat, and beautiful. The wiring methods of the same components of the same contract shall be consistent.



2.3 Requirements for the cross-sectional area of the secondary line:

Single wire ≥ 1.5mm²

Stranded wire ≥ 1.0mm²

Weak current circuit ≥ 0.5mm²

Current loop ≥ 2.5mm²

Protective grounding wire ≥ 2.5mm²

2.4 There should be no joints between all connecting wires.

2.5 At most 2 wires are allowed to be connected to the contacts of each electrical component.

2.6 The connection point of each terminal block is generally not suitable to connect two wires. In special circumstances, if two wires must be connected, the connection must be reliable.

2.7 The secondary line should be far away from the arcing components and should not hinder the operation of the electrical appliances.

2.9 The connection between the ammeter and the shunt shall not pass through the electric terminal block. The cable length shall not exceed 3 meters.

2.10 The connection between the ammeter and the current transformer must pass through the test terminal.

2.11 The secondary line shall not pass between the bus bars.



2.12 Connection of Profibus plug with resistance (suitable for connection of a cable)

When only one cable is connected, the wire is connected to the first interface.

Push the switch to the "0N" position.

The braided shielding tape is accurately placed on the metal guide.



2.13 Connection of Profibus plug with resistance (for the connection of two cables)

The two wires connected are in series within the plug. 

Push the switch to the "OFF" position. 

The braided shielding tape is accurately placed on the metal guide.



2.14  Connection of Profibus plug without resistance

The braided shielding tape is placed exactly flat on the metal guide.

The two red and green wires in the guide are placed on the knife-edge terminal blocks.

Green wire: connection point A

Red wire: connection point B



2.15 Connection of pull-back spring terminal block

Wire stripping length: 10mm

When the wire is inserted into the terminal port, until you feel the wire has been inserted to the bottom.



2.16 Connection of Profibus shielded cable in the drawer

Tighten the shielded wire until it is about 15mm long.

Use a wire nose to press the wire and the shield together.

The pressed wire is folded back on the outer layer of the insulated wire.



Use heat shrink tubing to fix the wire connection part.



3. Primary circuit wiring

3.1 Rectangular copper bus bars should be used as much as possible for primary wiring. When the rectangular bus is difficult to process or the current is less than or equal to 100A, insulated wires can be used. The cross-sectional area of the grounding copper busbar = the single-phase cross-sectional area of the incoming busbar of the electrical cabinet x 1/2

Grounding busbar and grounding terminal block connector:




The following is the wrong connection:



3.2 The confluence bus should be selected according to the design requirements. The main incoming cabinet and the contact cabinet bus are selected according to the confluence. The selection of the branch bus bar should be based on the rated working current of the release of the automatic air switch. If the automatic air switch does not have a release, the rated current value of the switch shall prevail. If there are several branch circuits under the automatic air switch, if the branch circuit is also equipped with an automatic air switch, select the branch bus section according to the above principles. If there is no automatic air switch, such as only a knife switch, a fuse, a low-voltage current transformer, etc., the cross-section of the branch bus is selected based on the rated current value of one side of the low-voltage current transformer. If these are not available, it can be selected according to the rated current of the contactor. If there is no contactor, the final selection is based on the rated current value of the fuse core.

Main circuit routing:



The correct connection for the branch circuit bus (red circle):



Wrong connection method of branch circuit bus (red circle):



3.3 The selection of current-carrying capacity of copper busbars needs to consult relevant documents. When the PVC insulated wire is in the wire groove, or when the wire runs in a bundle, or when the protection level is higher, the margin should be considered.



The following is the wrong connection:



3.4 The bus bar should avoid the arcing area.

3.5 When the AC main circuit passes through the metal frame forming a closed magnetic circuit, the three-phase bus bar shall pass through the same frame hole. If the wiring is not standardized, you must strip off the outer layer of the large cable that enters the trunking, and press all the wires into the trunking.

3.6 When there is friction between the cable and the cabinet metal, a rubber gasket should be added to protect the cable.



The following is the wrong connection:



3.7  When the cable is connected to the panel and door, it is necessary to add a plastic pipe and install a wire slot. In order to prevent the sharp edges from cutting the insulation layer on the outlet part of the cabinet, a plastic sheath must be added.



The following is the wrong connection:



3.8 When any two metal parts in the cabinet are connected by screws. If there is an insulating layer, a grounding washer of the corresponding specification should be used, and the tooth surface of the washer should be contacted with the surface of the part to ensure the continuity of the protection circuit.


3.9 When external wiring is required, the distance between the wiring terminal blocks and component contacts should not be less than 200mm from the bottom of the structure, and necessary space should be provided for connecting cables.


3.10 Improve the shielding function of the cabinet. If external wiring is required, electromagnetic shielding gaskets should be added when the wires are discharged. The requirements for the cabinet holes are: the length of the slot or the aperture is less than λ/(10-100). If you need to open ventilation windows in the electrical cabinet, staggered holes or grids with high frequency distribution are better than slits. The slits will conduct high-frequency signals in the electrical cabinet. The wiring between the cabinet body and the cabinet door must be sheathed, otherwise the insulation layer will be easily damaged.


The cabinet door is not grounded

The cabinet door wiring must be added with a wire slot



3.11 Bolt tightening identification

A. The bolts tightened in production should be marked blue.

B. The bolts tightened after testing should be marked red.



3. 12 Please wear gloves when assembling the copper busbar.


1) The drawer unit (especially 100mm mold height) should have a margin on the length of the secondary cable connected to the secondary connector.

2) When punching copper bars, attention should be paid to deburring, especially for square holes.

3) The thickness of the insulating support should not be greater than 10mm, so pay attention to inspection.

4) Read the manual before installing the components, otherwise it will be difficult to find out after installation.

5) Mechanical interlocking of drawers. Especially for IP42, the thickness of the sealing strip should be considered, or sharp corners should be ground.

6) The strength of the button spring of the drawer unit should be improved.

7) After the large cross-sectional area copper bar is connected, use a feeler gauge to recheck, and pay attention to the use of flat washers.

8) The terminal blocks of different voltage levels should be separated.

9) Pasting of signs. To use 3M glue, use 502 glue to click.

10) Double-sided tape can not be used to paste the wire groove inside the door, 502 glue can be used. Be careful not to leave gaps.

11) The wire slot for external wiring terminals should be enlarged.

12) The wire duct should not be too close to the output terminal block of the main circuit.

13) The zero sequence transformer should be connected with its own copper bar.

14) The finished cabinet shall be inspected before delivery.

15) The wire should be sheathed when passing through the partition.

16) There should be no joints in the middle of the wires.

17) The cable support should be reasonable.

18) Consider the safety of installation and maintenance.


4. Electric cabinet layout

4.1 Ensure that all equipment in the drive cabinet is well grounded. Use a short and thick ground wire to connect to a common ground point or ground bus. Any control equipment connected to the inverter (such as a PLC) should share the same ground with it, and also use short and thick wires to ground. It is best to use flat conductors (such as metal mesh) because of their low impedance at high frequencies.



4.2 The low-voltage unit of the electric cabinet. Relays and contactors can be protected when using fuses. When the situation of the main power grid is unknown, it is recommended to add a line reactor.

4.3 Ensure that the contactor in the conduction cabinet has arc extinguishing function. The AC contactor uses an R-C suppressor, and the DC contactor uses a "flywheel" diode, which is installed in the winding. Varistor suppressors are also very effective.

The picture below shows the reverse diode on the contactor.



4.4  If the equipment is operating in a noise-sensitive environment, EMC filters can be used to reduce radiation interference. At the same time, in order to achieve the best results, ensure that there should be good contact between the filter and the mounting plate.




4.5 The signal should enter the electrical cabinet from one side, and the shielding layer of the signal cable should be grounded at both ends. If not necessary, avoid using long cables. It is better to use shielded cables for control cables. The transmission line of analog signal should use double shielded twisted pair. It is best to use double-shielded twisted pair for low-voltage digital signal lines, or single-shielded twisted pair. The transmission cables for analog signals and digital signals should be shielded and routed separately. Do not share the same cable duct for 24VDC and 115 / 230VAC signals! Where the shielded cable enters the electrical cabinet, the external shielding part and the electrical cabinet panel shall be connected to a large metal table.


4.6 The motor cable should be routed independently of other cables, and the minimum distance is 500mm. At the same time, avoid long-distance parallel routing of motor cables and other cables. If the control cables and power cables are crossed, they should be crossed at 90° as much as possible. At the same time, the shields of the motor cables and control cables must be fixed to the mounting plate with suitable clips.


4.7 In order to effectively suppress the electromagnetic radiation and conduction, the motor cables of the inverter must be shielded cables. The conductance of the shielding layer must be at least 1/10 of the conductance of each phase conductor.


4.8 The central grounding bar group and PE conductive bar must be connected to the beam (metal to metal connection). They must be located directly opposite the cable gland. The central ground bar is additionally connected to the protection circuit (ground electrode) through another cable. The shielded bus is used to ensure reliable shield connection of each cable. It realizes a large-area metal-to-metal connection through a beam.



4.9 The operation panel with display cannot be installed near cables and equipment with coils, such as power cables, contactors, relays, solenoid valves, transformers, etc., because they can generate strong magnetic fields .


4.10 Power components (transformers, drive components, load power supplies, etc.) and control components (relay control parts, programmable controllers) must be installed separately. But it is not suitable for products in which the power part and the control part are designed as a whole. The metal shells of the frequency converter and related filters should be connected to the electrical cabinet with low resistance to reduce the impact of high-frequency transient current. The ideal situation is to install the module on a black metal plate with good conductivity and install the metal plate on a large metal table. Painted electrical cabinet panels, DIN rails or other devices with only small supporting surfaces cannot meet this requirement.

The following figure shows the basic layout of an electric cabinet:



4.11 Pay attention to the EMC regional principle when designing the control cabinet, and plan different equipment in different areas. Each area has different requirements for noise emission and immunity. It is better to isolate the area in space with a metal shell or a grounding partition in the cabinet. And taking into account the heat generation, the installation of the air inlet fan and the air outlet fan, generally the equipment with a large heat generation is installed near the air outlet. The inlet fan is generally installed at the lower part, and the outlet fan is installed at the upper part of the cabinet.



4.12 According to the protection level of the equipment in the electric cabinet, the dust-proof and moisture-proof functions of the electric cabinet need to be considered. The commonly used equipment are mainly: air conditioners, fans, heat exchangers, and anti-condensation heaters. At the same time, choose equipment of different power according to the size of the cabinet. Regarding the selection of the fan, the main consideration is the normal working temperature inside the cabinet and the highest ambient temperature outside the cabinet to obtain a temperature difference. According to the air exchange rate of the fan, estimate the air volume in the cabinet. Knowing three data: temperature difference, air exchange rate, air volume, find the time for the air in the cabinet to change once. Then calculate the actual air exchange rate through the temperature difference calculation, so as to select the actual fan. Because the temperature drops at night, condensed water will be generated and attached to the circuit board in the cabinet, so it is necessary to select the corresponding anti-condensation heater to maintain the temperature in the cabinet.




5. Daily maintenance and overhaul of electric cabinet

5.1 Check the surrounding environment of the electric cabinet. Use a thermometer, hygrometer, and recorder to check whether the electric cabinet is frozen when the ambient temperature is between -10℃ and +50℃ and the surrounding humidity is 90%.

5.2 Check whether all the devices have abnormal vibration or abnormal sound

5. 3 Check whether the main circuit voltage of the power supply voltage is normal

5.4 Disconnect the wiring of the inverter, short-circuit the terminal blocks R, S, T, U, V, W together, and measure the insulation resistance between them and the grounding terminal with a DC500V class megohmmeter. Should be more than 5M ohms, strengthen the fasteners, and observe whether there are signs of heat generation using observation elements.

5.5 Check whether the terminal block is damaged, whether the conductor is skewed, and whether the outer layer of the wire is damaged.

5.6 Check whether the filter capacitor is leaking liquid or swelling. The static capacitance measured with a capacity tester should be above 85% of the rated capacity. Check whether there is a "Be, Be" sound when the relay is activated, and whether the contact is rough or broken. Check if there are cracks in the resistor resistor insulation, and confirm if there is any disconnection.

5.7 Check whether the output voltage of each phase is balanced when the inverter is running. Perform sequence protection operation test, display, and check whether the protection circuit is abnormal.

5.8 Check whether the cooling system has abnormal vibration, abnormal sound, and whether the connecting parts are loose.

Sun Electric Co., Ltd
Founded in 2011, Sun Electric Co., Ltd specializes in the production of terminal blocks and industrial electrical connection products.

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