Solution for overvoltage protection of small-capacity UPS power supply. In the use of many small-capacity UPS power supplies, some difficult problems will always be encountered. The effectiveness and cost of overvoltage protection measures are closely related to the selection of equipment and designs. As a power supply system, UPS power supply must have line connections from many aspects, including mains AC input, UPS AC output, communication interfaces, etc. Strictly speaking, these three ports should be equipped with overvoltage protection.

　　The meaning of UPS power supply overvoltage protection includes:

　　1. Various surges or voltage spikes from the outside have a certain impact on the UPS and require protection.

　　2. These surges or voltage spikes may affect the load through the UPS, and protection is required if necessary.

　　For data centers or control centers equipped with large UPS, the building or computer room where it is located usually has a relatively complete overall lightning protection system, and the residual value of overvoltage reaching the UPS end is not high; while the use environment of small UPS power supplies is relatively poor, except for the protection against lightning. Lightning, surge protection against operating overvoltage on the surrounding power grid should also be considered.

　　Solutions for overvoltage protection of small-capacity UPS power supplies:

　　In the use of UPS power supplies, the cost of overvoltage and its components play an important role in the service life of the UPS power supply and the selection of overvoltage protection solutions. Generally speaking, small-capacity UPSs do not mainly consider lightning protection, but rather Protection against overvoltage in power supply operation.

　　There are two solutions for overvoltage protection of small-capacity UPS power supplies. One solution is to increase the current flow capacity of MOV, such as using 20D471, 25D471 or even 32D471 MOV devices to increase the current flow capacity to about 10kA to 25KA. In this way, it can not only withstand long-term or periodic over-voltage energy discharge, but also keep the residual voltage on the line at a low level. However, this will greatly increase the cost of protection.

　　The second option is to increase the operating voltage of the MOV. For example, use MOV devices such as 14D561 or 14D621 to increase the operating voltage from 470V to 560V or 620V. In this way, the operating probability of the MOV is greatly reduced without changing the current capacity. and energy-reducing time without increasing costs. However, this will increase the residual pressure on the line.

　　Gas discharge tube (GDT) is a new type of SPD equipment that is suitable for use because its price is relatively cheap.

　　Compared with MOV, GDT has the following important features:

　　1. GDT has better repetitive discharge characteristics than MOV and is not easily damaged.

　　2. MOV is a clamp-type component, while GDT is a short-circuit type component. Once the GDT operates, it will be in a low-resistance state similar to a short circuit. The short-circuit operation will last for about half a cycle (10ms) and will not be interrupted until it crosses zero. Therefore, gas discharge tubes generally need to be used in conjunction with short-circuit protection equipment.

　　3. The operating voltage accuracy of GDT is lower than that of MOV. Generally, the operating voltage accuracy of MOV is ±10%, while the operating voltage accuracy of GDT is ±20%.

　　For outdoor UPS, due to frequent lightning surges and operating overvoltage, considering that the recovery of short-circuit protection equipment is inconvenient, it is generally not suitable to directly use gas discharge tubes as overvoltage protection equipment. Because MOV and GDT have different functional characteristics, their functions are also quite different. Ideal overvoltage protection equipment requires small leakage current, fast action response, low residual voltage, and resistance to aging. However, the existing single equipment cannot fully meet the requirements.

　　Finally, I would like to remind everyone that a reasonable UPS power supply overvoltage protection solution can not only withstand long-term or periodic overvoltage energy discharge, but also keep the residual voltage on the line at a low level. So we must choose a good overvoltage protection solution for ourselves. Different UPS power supply overvoltage solutions are used for UPS power supplies in different periods. In the early days, due to cost considerations, small-capacity UPSs were similar to other ordinary power supply products. Generally, 14D471 zinc oxide varistors were used for 220Vac input EMI. (MOV) for over-voltage protection.

　　The above solutions are introduced to solve the problem of overvoltage protection of small-capacity UPS power supply. In addition, there are other solutions. In short, users need to choose a protection solution that suits them according to their actual situation. Under the condition of lower cost, choosing and designing appropriate overvoltage protection measures has become an important part of modern UPS applications.

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