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Are you still confused about what current rating fuse to use for distribution transformers? By referring to the rated performance data for distribution transformers provided by Changhui Instruments, along with the table showing the appropriate fuse ratings for the high-voltage and low-voltage sides, you can quickly determine the appropriate amperage of fuse for the distribution transformer you are using. Rated performance data of distribution transformers and comparison table of fuses on the high-voltage and low-voltage sides. Transformer fuses: yunrun.com.cn/tech/1773.html. Capacity in KVA, rated current on high-voltage side in A, rated current on low-voltage side in A, rated current of high-voltage side fuse in A, rated current of low-voltage side fuse in A: 10 – 0.577, 14.4; 2 – 30, 20; 1.15, 28.9; 3 – 50, 30; 1.73, 43.3; 5 – 60, 50; 2.89, 72.2; 5 – 120, 75; 4.33, 108; 10 – 150, 100; 5.77, 144; 10 – 300, 180; 10.4, 260; 20 – 350, 240; 13.9, 346; 25 – 400, 320; 18.5, 462; 30 – 500, 560; 32.3, 808; 50 – 900. Principles for selecting transformer fuses: The selection of transformer fuses should be based on the ampere-second characteristic curve of the fuse. If no characteristic curve is available, the following rules shall be followed for selection: ① The rated current of the primary fuse shall be selected as a multiple of the transformer’s rated current; for transformers with a capacity of 10–100 kVA, this multiple is 1–3 ； For transformers of 100 kVA and above, it is 1.5–2 times. ②When multiple transformers share a single fuse bank, the rated current of the fuse is selected to be 1.0–1.5 times the sum of the rated currents of all the transformers. ③The rated current of the secondary fuse is selected based on the rated current of the transformer’s secondary side. ④For a dedicated transformer for a single motor, taking into account the impact of starting current, the rating current of the secondary fuse can be selected at 1.3 times the rated current of the transformer. ⑤The selection of fuses should take into account the coordination with upper and lower level protections. Dry-type transformer temperature controller: yunrun.com.cn/product/1169.html. Selection of high-voltage fuses: The maximum rating of high-voltage fuses should not exceed 40A; the higher the rating, the longer it will take for the fuse to blow in case of a fault. According to the fusing characteristic curve of the fuse, the current required to cause it to fuse within 0.1 second should be no less than 20 times its rated current; that is, when the short circuit occurs at the branch main line, the short-circuit current may need to reach 800A for the fuse to fuse within 0.1 second. The current at which the fuse blows within 0.5 seconds is therefore 4 times the fuse’s rated current, namely 160A. Selection of low-voltage fuses: The fuses on the low-voltage side of the transformer can be chosen based on the rated current or overload capacity of the transmitter; generally, a 20% overload factor is taken into account. For the selection of fuses on branch circuits or in redundant fuse systems, it is necessary to ensure selectivity among the various fuses. Between the two levels of protection, the rated current of the fuses should differ by at least one level. The fuse installed on the high-voltage side of the transmitter should work in coordination with the relay protection devices of the power supply circuit. The fuse blow time should be less than the operating time of the relay protection on the power supply side. Precautions for the installation and use of high and low voltage fuses in distribution transformers: 1. When installing the fuses, it is necessary to control the amount of force applied to avoid damaging the fuses due to excessive force. Fuses that have been in use for a period of time often change their original placement and points of stress, a fact that electrical professionals must be aware of; otherwise, in the event of a power grid failure, it is possible for the current to increase without ensuring that the fuse blows in a timely manner. 2. When tightening the fuse, it is necessary to follow the operating specifications strictly to prevent the end of the fuse from twisting and breaking as the bolt rotates. Otherwise, if the power grid operates for an extended period, excessive heat can easily cause the fuse to burn out, leading to false tripping of the circuit breaker. 3. The metal castings at both ends of the fuse have sharp corners; after the fuse has been in use for some time, external vibrations can cause friction between the fuse and the castings, leading to the fuse breaking and then falling off freely. The most reliable method is to grind the sharp edges of the casting during installation, and to regularly check whether the position of the fuse has changed over time as it is in use.