Fuse is a kind of electronic components, is the safety protection device in the circuit, can be used to protect the electrical equipment from excessive current damage. There are many types of fuses, including self-recovery fuses, thermal fuses, current fuses and so on. When choosing a fuse, you need to know the fuse model specifications, this article will introduce the fuse model specification and selection method.

How to choose the specifications of the fuse

1、Safety certification: first of all, you need to decide the safety certification of the fuse according to the safety certification of the whole machine, such as UL specification or IEC specification.

2、Structure size: It is necessary to determine its size according to the space designed in the circuit, such as length, diameter, whether it is with a lead, etc..

3、Rated voltage: it must be greater than or equal to the actual applied voltage, generally 24V, 32V, 63V, 125V, 250V, etc.

4、Breaking capacity: should be greater than the maximum fault current in the circuit.

5、Rated current: refer to the following items to be determined:
(1) Normal operating current, operating at 25℃, the rated current of UL specification fuse ≥ normal operating current/0.75; IEC specification fuse ≥ normal operating current/0.9.
(2) Ambient temperature: the current carrying capacity test of the fuse is conducted under the condition of ambient temperature of 25℃, the higher the ambient temperature, the shorter the life of the fuse, the lower the carrying capacity, so the selection of fuses should consider the ambient temperature.
(3) Pulse: Pulse will produce thermal cycle and mechanical fatigue that will affect the life of the fuse, in the design should make the pulse I2T in the consideration of the pulse factor under the premise of less than the nominal melting thermal energy of the fuse I2T, the fuse rated I2T> the actual pulse I2T/Pf. Pf: Pulse Factor, according to the number of times it can withstand the pulse different and different.
6、Testing: The samples selected after the above procedure need to be tested in actual circuits to verify the suitability of the selected fuses. This verification should include tests under normal conditions and fault conditions to ensure that the selected fuses provide protection in the circuit being protected.

Precautions for selecting fuses

1、Can not use too thin fuses, the use of thin fuses, through the normal current is also easy to burn out, resulting in unnecessary power outages. Can not choose too thick fuse, too thick current is not easy to be burned, but also easy to lead to fire.
2、Must choose and use the appropriate fuse, fuse melting current is usually 1.5 ~ 2.0 times the rated current. Such as the normal use of electricity in the family, the total power of each appliance and more than 1100 watts of the choice of 5 amperes of fuse, the use of 0.98 mm diameter 20 fuse can be, when the current exceeds 7.5 amperes to 10 amperes, the fuse will automatically blow to achieve the purpose of protection.
3、If the selection and use of fuses in line with the specifications and the phenomenon of frequent fuse blowing, indicating that the electrical wiring and electrical equipment has a problem, should promptly ask the electrician to find the cause, to remove the hidden danger. Do not arbitrarily replace the thick fuse and simply use copper wire, iron wire and so on instead.