1. Select the model of the fuse according to the circuit requirements and installation conditions. For circuits with small capacity, choose semi enclosed or unfilled enclosed; The choice for high short-circuit current is the enclosed type with fillers; Select fast fuses for semiconductor component protection.
2. Select the rated voltage of the fuse according to the line voltage.
3. Select the rated current of the fuse according to the load characteristics.
4. The selection of different levels of melts requires mutual coordination, with the latter level being smaller than the previous level. The current on the main switch and each branch line is different, and the selection of fuses is also different. If a short circuit occurs in the circuit, the 15A and 25A fuses will fuse simultaneously, and the protection characteristics will lose selectivity. Therefore, only by maintaining a 2-3 level difference between the main gate and the branch can such a phenomenon not occur. If the low-voltage side outlet of a transformer is RT0 1000/800, the motor is RT0 400/250 or RT0 400/350, and the rated current ratio between the upper and lower levels is 3.2 and 2.3 respectively, the selectivity is good, that is, if the branch circuit experiences a short circuit, the fuse of the branch circuit will not affect the overall power supply.
5. The melt should not be too small. If the selection is too small, it is easy to cause one phase fuse to blow, causing the motor to run single-phase and burn out; According to statistics, 60% of burnt out motors are caused by improper insurance configuration.
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