Illustrated Wiring: Comprehensive Review of Electrical Cabinet Sets

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At the invitation of the users of the “Technical Forum” on Yingchanghui Instrument Network, I was asked to provide my feedback on the electrical cabinets shown in the two pictures they posted. I’ll be honest and straightforward, offering my humble opinions; if there are any inaccuracies or inappropriate comments, I kindly ask the other users to point them out at once. Thank you very much! For more information about Changhui Instruments, visit http://www.yunrun.com.cn. Based on my years of work experience, designing electrical cabinets can be considered a “challenging task.” To this day, I haven’t managed to create a perfect electrical cabinet yet – there’s always something that needs improvement each time one is completed. Perhaps this is what drives us to keep improving. But regardless of our current level of expertise in this field, there is one principle I’d like to share with everyone: “Functionality comes first, followed by reliability and durability; ease of maintenance is important next, then convenience in manufacturing, and finally aesthetics and neatness.” The first three points are the most crucial, while for the latter two, compromises may sometimes be necessary, as everything is ultimately constrained by cost factors. I also base my comments on this principle; here, as is my habit, I only point out the areas that I feel are clearly inadequate. Just because I don’t mention something doesn’t mean there’s no issue – it could be that I missed it, or it might not be that important. Of course, it’s best if there are no problems at all. http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020816172890.png Figure 1: Problems existing in the complete set of cabinet components. 1. The overall wiring design is unreasonable; it is not aesthetically pleasing nor safe. There is insufficient space above and below the wiring switches, and no separators are installed between the wires connected to the switches. This results in significant stress between the cables and the terminals. It is recommended to use a copper bar structure for wiring, and to equip the switches with handle mechanisms for operation. 2. The three-phase copper bars installed on the top of the cabinet are used to supply power to the loads inside the cabinet; this approach represents an overkill and leads to significant waste. Moreover, complete insulation is not achieved, so it is still necessary to install transparent acrylic partitions. It is recommended to use a smaller busbar structure for efficient distribution of high-voltage power. 3. No incoming circuit breaker was found to be assigned to the isolation transformer, and one section of the transformer’s secondary output was not grounded. 4. The guide rails of the PLC rack are not grounded, and the shielding layer of the communication cables for the PLC’s interface communication modules has not been grounded for shielding due to the lack of such treatment in front of the modules. 5. The 24V power supply does not use a busbar system for power distribution; as a result, all loads may end up being connected to the terminals of the first device that is connected to the 24V power supply. 6. There is a single grounding point for the entire cabinet, and it seems that the three cabinets are disconnected from each other and not properly connected ； The layout of the grounding bars is also unreasonable, resulting in inconvenient and unsightly wiring from the grounding wires to the grounding copper bars ； The system also lacks proper layered grounding, such as the installation of small grounding strips under the PLC rack. 7. The position of the outlet terminals is set improperly – it is too high, and they are far away from the grounding bar. This makes it difficult to connect the cables to the motor, reduces aesthetics, results in many cables hanging loosely, and places excessive stress on the terminal bar. 8. For the intermediate cabinet, the two infeed cables with higher power that use frequency conversion seem too small; shielded cables are not being used for the outfeed cables connected to the terminals. At the outfeed terminals, it appears that there are other control terminals mixed in among those related to the motors – could these be used for controlling the motor cooling fans? It also seems that there aren’t enough grounding terminals, and it’s difficult to see clearly. 9. The frequency converter in the intermediate cabinet is also not properly grounded; there is no grounding for the incoming and outgoing wires, and the shielding at the DP communication terminals is likewise not grounded. 10. In the right cabinet, the Simotion or S120 system is installed at too high a height, which makes it difficult to run cables directly from the device; moreover, there are no fixing clamps for the cables exiting from that area. 11. CU and SMC can be placed on the right side of the motor module, allowing the rectifier unit and the incoming line reactor to be arranged closely together for easy wiring; this also makes it simpler to carry out wiring maintenance on the SMC. 12. In the right-side cabinet, the arrangement of the circuit breakers and sockets on the top layer is unreasonable and unsightly ； The terminal arrangement on the right side of the S120 is unreasonable. 13. All mounting bases are not grounded. 14. The grounding of the cabinet doors seems to be connected to the painted, insulated door frames. 15. The installation position of the wiring holder at the bottom layer is unreasonable and arbitrary. 16. The overall layout of the system is not very reasonable; the high-voltage systems surround the low-voltage systems, and the grounding measures are inadequate, making it difficult to address interference issues. Figure 2: Problems existing in the electrical cabinet assembly http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020816200581.png Figure 2: 1. Similar to the problems in 10, 11, and 12 of Figure 1, the wiring is a bit messy. 2. The overall wire diameter seems too small, especially that of the ground wire. 3. The main incoming circuit breaker does not have auxiliary contacts connected to the CU, nor is the main contactor controlled by the CU to regulate the main power supply. 4. The shielding layers of the motor wires and encoder wires have not been grounded repeatedly. References for electrical cabinet assemblies (some images provided by netizens)
1. Main power inlet of the electrical cabinet: http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020816214940.png
2. Busbar structure: http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020816224230.png
3. Door handles and small distribution structures: http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020816232072.png
4. Small busbar structure: http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020816235921.png
5. DC24V power supply, busbar structure: http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020816242747.png
6. Grounding of the power supply: http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020816250253.png
7. Grounding of the PLC: http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020816255637.png
8. Grounding of the inverter: http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020816263135.png
9. Main grounding of the cabinet: http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020816271279.png
10. Terminal and cable clamps: http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020816282915.png
11. Simotion cabinet assembly: http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020816290036.png

Summary:
1. A good electrical cabinet is the result of proper design – it requires standards and detailed designs that must be accurately reflected in the drawings. Only then can the manufacturing party produce it properly. Design engineers should not blame the manufacturing party for poor work; instead, they should first check whether they have designed the drawings properly. 2. Design engineers must maintain good communication with the manufacturers responsible for the assembly work, especially when it comes to new drawings. It is best to go to the site personally during the initial layout phase to see whether the actual arrangement matches the design, and to listen to the suggestions of the workers on site. This helps avoid making decisions in isolation; sometimes a drawing may look fine on paper, but its practical implementation may not be reasonable, even leading to difficulties in processing and wiring. In such cases, the advice of experienced workers is very valuable, and it is important to take that advice into account and make necessary adjustments promptly. Remember not to try to cut corners by ignoring these suggestions, nor to be stubborn and refuse to change your approach. 3. It is necessary to develop a set of processing techniques and standards suitable for oneself, cultivate the good habit of carrying out processing according to the drawings, clarify roles and responsibilities – the design engineer is responsible if there are errors in the drawings, while the processing party is responsible if the work is not carried out as per those drawings. 4. Implement a strict factory acceptance system, conduct inspections in strict accordance with the drawings, and require rework if there are any discrepancies. 5. Summarize the experiences and lessons learned from each design and manufacturing process in a timely manner, and keep records of these summaries for use as references and to facilitate improvements in similar designs in the future. 6. Even during the process of assembling the units, design engineers should, if possible, spend more time in the workshop, pay attention to the electrical cabinets they designed that are being assembled, and communicate more with those responsible for the assembly on site: ① Keep track of the progress of production and assembly ； ②Identify and resolve promptly the problems encountered in actual production or issues related to detail handling (especially when the cable tray covers have not yet been installed) ； ③It is advisable to take more photos of the electrical cabinets at various stages of processing, so as to have image records available for comparative analysis in subsequent design work, thereby facilitating improvements. The images below show the different stages in the manufacturing process of electrical cabinets. http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020816294430.png http://www.yunrun.com.cn/News/UploadFiles_5183/201602/2016020816300952.png