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This post was last edited by yunrun on 2016-3-8 at 01:22. Engineers from Changhui Instruments share, through pictures and text, the common problems associated with PLC electrical cabinets. It’s a valuable resource containing useful knowledge on electrical assembly and installation. By comparing the information in the pictures and text, you can determine whether the electrical equipment you’re using has any issues that need to be addressed. Don’t forget to share this article with your friends after reading it! Changhui Instruments: http%3a//www%2eyunrun%2ecom%2cn http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020619130273.png Problems in electrical panel assembly: 1. Multiple wires are connected together at the outlet side of the circuit breaker; 2. Multiple loads are connected together at the inlet side of the circuit breaker; 3. The wire diameters at the inlet and outlet sides of the circuit breaker are the same; 4. Wires of different diameters are connected together arbitrarily; 5. Cable colors are not used in a standardized manner. Definitions of common wire colors: 1. Three-phase AC: yellow/green/red; 2. Single-phase AC: red; 3. 24V DC: blue; 4. I/O wires: gray; 5. Analog signals: white; 6. Neutral wire: light blue; 7. PE wire: yellow-green. http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020619133203.png Problems in electrical panel assembly: 1. Incorrect grounding points, resulting in no effective grounding; 2. Failure to connect to the system’s PE wire. http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020619141951.png Problems in electrical panel assembly: 1. No use of braided straps for grounding, and grounding wires are not twisted into loops; 2. Failure to connect to the system’s PE wire. http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020619145013.png Problems in electrical panel assembly: 1. The cross-sectional area of the grounding bar is smaller than that of the incoming wires; 2. Excessive holes in the grounding bar further reduce its cross-sectional area; 3. Connecting wires together for grounding increases grounding impedance; 4. Neither the installation base nor the frame of the cabinet is grounded; 5. No measures are taken for layered grounding. http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020619152976.png Problems in electrical panel assembly: 1. Communication cables are laid parallel to high-voltage cables; 2. The shielding layer of communication cables is forced to be grounded at insulating parts. http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020619161829.png Problems in the assembly of frequency converter cabinets: 1. The signal wires of the drive units are hanging freely, without any fixation or shielding grounding. 2. The drive unit is not installed properly; it should be placed in a separate cabinet along with the incoming line filter reactor. Panel mounting is not suitable, and a frame-based installation method should be used instead. 3. The cable from the large drive unit to the motor should generally not pass through terminals as an intermediate link, but should run directly from one end to the other. 4. The motor cable should be a shielded cable, and the shielding layer should be clamped. 5. The layout design of the system’s power inlet is unreasonable, blocking the cooling air ducts of the drive device. 6. Terminals should not be used for the main incoming cable; instead, a cable compression method using copper busbar components should be employed. http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020619165745.png Problems existing in electrical panel assembly: 1. The DP bus is not properly fixed or shielded, and the accessories required to fix and shield the cables for the CU320 module are missing. 2. The encoder cable and the device communication cable are left hanging without being fixed, and the encoder cable is also not shielded. 3. Neither the CU320 control unit nor the interface module has been grounded. 4. The transmission mechanism lacks shielding accessories, is installed at too low a position, and is blocked by cable trays, which results in the cooling air ducts being obstructed as well as improper wiring for the mechanism. 5. The design of the cable entry point for the cabinet is unreasonable. http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020619173938.png Problems in electrical panel assembly: 1. The main switch outlets are connected in parallel, which increases contact resistance and leads to overheating. 2. The design structure of the busbar is unreasonable; the incoming and outgoing wires are in disarray, and large-cross-section wires show coiled wiring patterns. 3. The insulation distance between the busbars and the base plate, between the busbars themselves, and between the wires of different phases is insufficient. 4. The cross-sectional area of the busbar is smaller than that of the incoming cable, and numerous holes are drilled, which further reduces the effective cross-sectional area and thus lowers the current-carrying capacity. 5. The various output circuits of the busbar lack current-limiting protection, which makes it very easy for a short circuit in a minor circuit to lead to a short circuit across the entire circuit, thereby causing serious accidents such as fires. 6. The cable colors are not used in a standardized manner. http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020619202072.png Problems in electrical panel assembly: 1. High-voltage wires and signal wires are bundled together when routed. 2. The shielding layer of the communication wires is left unsecured, and the instruments are not properly grounded. 3. The structure for installing cables across doors is unreasonable, making it easy for the wires to break. 4. Cables in cabinet doors should also be routed using conduit, with wires organized in categories. http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020619212847.png Problems in electrical panel assembly: 1. The heating control wires for the temperature control module are not made of twisted-pair shielded wires. 2. Aluminum guides are used, but there are no grounding terminals. 3. The grounding method for communication wires is incorrect, resulting in poor grounding effectiveness. 4. The signal wires for thermal resistors are not shielded cables, and a 3-wire or 4-wire configuration with higher measurement accuracy is not used. http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020619222845.png Problems in electrical panel assembly: 1. The high-voltage terminals are located below the signal terminals, with very little space between them. 2. High-voltage wires and signal wires are laid parallel to each other in the same conduit. 3. The cables entering the cabinet are not secured with clamps, nor are they shielded and grounded. 4. No grounding busbars are used in the cabinet. 5. There is no proper separation between high-voltage and low-voltage terminals. http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020619234599.png Problems in electrical panel assembly: 1. The overall design of the temperature control heating cabinet is unreasonable, leading to wasted space and complicated wiring. 2. Mixing strong and weak electrical wiring – the weak electrical control units should never be designed in this area. 3. Devices that are used for extended periods of time should not be powered by household sockets; the cables should not be left hanging unrestrained for long periods, and there should be no grounding or circuit breaker protection. 4. There is a design featuring high single-phase current, and the overload protection mechanism may be faulty. 5. It is necessary to verify whether the load power matches the diameter of the wires. 6. It is necessary to verify whether the circuit breaker matches the load. 7. The solid-state control signal wires and power wires run parallel in the same conduit. http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020619325009.png Problems in electrical panel assembly: 1. The incoming and outgoing wires of the transformer are the same color. 2. One end of the secondary output is not grounded. 3. The load has no separate circuits nor protection. 4. The layout is unreasonable, taking up a lot of space. http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020619293615.png Problems in electrical panel assembly: 1. The AC and DC wires of the switching power supply are the same color. 2. The AC input terminal is not grounded. 3. The negative pole of the DC output is not grounded. 4. The wire gauge is unreasonable – it’s too small. 5. The load has no separate circuits nor protection. 6. The layout is unreasonable, taking up a lot of space. http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020619301369.png Problems in electrical panel assembly: 1. A filter may not be necessary. 2. If a filter is needed, its specifications should be chosen based on the actual load size; 20A is clearly too large in this case, so it won’t be effective. http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020619435967.png Problems in electrical panel assembly: 1. The grounding terminals are being used as fixing terminals. 2. Why does the bipolar circuit breaker have only one phase outlet? http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020621245733.png Problems in PLC cabinet assembly: 1. The layout of the cabinet is poor, resulting in wasted space; the wiring is messy, with power and control wires mixed together, and communication wires and power cables hanging randomly inside the cabinet. 2. PLC-related communication components should be arranged together, with proper equalization of potential and shielding to avoid tangled wires. 3. The communication wires form loops. 4. There are issues with the system design – why use two slave stations when one S7-300 rack should be sufficient to handle the I/O functions? 5. Use, principles, and design of safety relays: http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020621214140.png 1. The mounting rails are not grounded. 2. The input of the power module is not grounded, and the negative terminal of the output is also not grounded. 3. The signal wires are arranged in a chaotic manner, and the wire specifications used are not standard. 4. The communication wires and analog wires lack proper shielding. 5. Unused wire ends are left exposed without any protection: http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020621224855.png Problems encountered during PLC cabinet assembly: 1. The space allocated for the sub-stations is too large. 2. Aluminum rails should not be used; the mounting rails are not grounded. 3. The wire specifications used are not standard. 4. The communication wires and analog wires lack proper shielding: http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020621194299.png Problems encountered during PLC cabinet assembly: 1. Aluminum rails should not be used; the mounting rails are not grounded. 2. Neither the CPU nor the modules are grounded. 3. The wire specifications used are not standard. 4. The power supply for the EM277 module should not come from the CPU’s output; its capacity and voltage ripple levels do not meet the requirements, and there is a difference in potential levels. 5. The communication wires and analog wires lack proper shielding: http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020621271501.png Problems encountered during the assembly of electrical equipment: 1. The connection of the UPS power supply should not be done using sockets; terminal connections should be used instead. 2. The power supply lacks grounding protection. 3. The circuit does not have overload or short-circuit protection. 4. The wire gauge used is not appropriate. 5. Random wiring of unknown circuits. http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020621373657.png Problems in PLC cabinet assembly: 1. Neither the power supply nor the chassis of the industrial computer has been grounded. 2. The DP communication cables have not been re-shielded. 3. The industrial computer is not suitable for use as a host computer in the DP bus; since the main control frame is equipped with an Ethernet communication module, why not use Ethernet for communication? http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020621392684.png Problems in the installation of electrical equipment: 1. Do not use wall-penetrating methods for connecting cabinets; instead, use bases to pass the wires. 2. Communication cables, signal cables, power cables, and motor cables should not be routed together. 3. When making holes in walls, no rubber gaskets are used for protection, resulting in the cables coming into direct contact with the sharp edges of those holes. http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020621414381.png Problems in cable laying during electrical construction: 1. Cable trays with partitions are not used, or separate trays for strong and weak electrical circuits are not employed, with no separation between power cables and control cables. 2. The cable tray wiring is messy, with cables crossing each other. 3. The sequence of laying larger cables first and then smaller cables was not followed. 4. The cables in the cable trays are not secured, especially in those that run vertically. 5. The entire tray structure has not been grounded. http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020621515037.png Problems with electrical cabinets: 1. The design and layout of the individual cabinets are too crowded. 2. The placement of components is unreasonable, which hinders wiring. 3. There is a mix-up in the wiring for low-voltage and high-voltage circuits. 4. There are no adequate grounding measures in place. 5. There isn’t enough space for heat dissipation of drive and power components. 6. The design of the wiring entrances and exits in the cabinets is unreasonable. 7. The protection level of the cabinets does not meet the requirements of the installation site. Summary: 1. There is a lack of systematic design and overall planning. ① No comprehensive consideration has been given to aspects such as the structure of the control system, whether it should be centralized or distributed, the relationship between transmission and control functions, the distinction between main control units and auxiliary units, the network structure, and the layout of the cabinets. ②Network structure: Based on the structure of the control system determined, the system control bus and communication network are planned to define the network structure, transmission medium, wiring method, and wiring distance. ③Power supply structure: The power distribution of the system is not planned based on the structure of the control system that has been determined; there is no classification or segmentation of power supplies, nor any associated protection mechanisms, and no surge or overcurrent protection is available. ④Grounding system: There is no basis for determining the system grounding structure based on the control system architecture, network structure, or power supply structure; there is no design for classified, segmented, or hierarchical grounding. 2. Lack of norms and standards, as well as unified management. ① There are no unified design standards. ②There are no standardized drawing criteria. ③The complete set of technical specifications has not been installed. ④At both the system level and the component level, various selection decisions lack proper and accurate calculations, resulting in a high degree of randomness and arbitrariness. ⑤Sustainable improvement is even less possible.