The fuse is also known as the fuse, which is based on the current exceeds the specified value for a period of time, and the melt is used to open the circuit, thereby opening the circuit; the current protector made of this principle. The fuse is widely used in high and low voltage distribution systems, control systems and electrical equipment. The fuse is a short circuit and an overcurrent protector that is one of the widely used protection devices.
Cylindrical cap fuse
The outer shape is a cylindrical shape, and the rated current to 100A is used as an overload and short circuit protection.
Spiral fuse
In the fuse tube, there is a quartz sand, the melt is buried therein, and when the melt is blown, the arc is sprayed to the quartz sand and its gap, which can quickly cool down. The spiral fuse is rated from 5 to 200A, mainly used for short-circuit current large branch circuits or places with flammable gases.
Insert fuse
Intercropping fuses, known as porcelain-shaped fuses, refers to a fuse of a fuse in a conductive plug-in. It has the advantages of simple structure, low price, convenient replacement of melt, is widely used in short-circuit protection for lighting circuits and small capacity motors.
Closed fuse
The closed fuse is divided into a filler fuse and a filler fuse, two filler fuses, generally in a circuit of a square ceramic tube current level 1kA. Filled closed fuses Melt the melt into a closed cylinder, a slight breaking capacity, and a power grid or power distribution apparatus below 600A.
Fast fuse
The fast fuse is mainly used for short circuit protection of semiconductor rectifier elements or rectifiers. Due to the low overload capacity of the semiconductor components. Only with large overload currents in a very short time, short-circuit protection is required to have a fast fuck ability.
High voltage limit fuse
The high-voltage current limiting fuse is suitable for communication 50Hz, rated voltage 3. 6 ~ 12KV system, can also be used in conjunction with other appliances (such as switches, contactors, etc.) as an overload or short circuit such as electric equipment such as electric machines, transformers, capacitors, etc. Protect. Common models have RN XRNM XRN.
High pressure drop fuse
Most of the dry lines mounted on the high voltage side of the power distribution transformer, mostly for outdoor. The main functions have high protection performance requirements, which can be used in conjunction with isolation, instead of automatic air switches; can also be used with load switches, instead of price high circuit breakers. It also has short-circuit protection, overload, and isolation circuits.
High pressure spray fuse
It is mainly suitable for single overcurrent protection for high-voltage parallel capacitors in power systems, i.e. to cut off fault capacitors to ensure proper operation of the fault capacitor. Self-producing gas extinguishing structure. Under the arc action, the extinguped arc gas generated by the arc tube is higher than the velocity of the deionization rate than the arc ionization, while rapidly establishing the pressure discharge, thereby extinguishing the arc.
Select the model of the fuse according to the line requirements and installation conditions. Circuits with small capacity selection semi-closed or no filler closed; short-circuit current larger selectable filler closed; semiconductor component protection Select a fast fuse.
Select the rated current of the fuse based on the load characteristics.
Choosing the melt at all levels need to cooperate with each other, the latter level is small than the previous level, the current is different on the branch line, and the choice of fuse is different.
The rated voltage of the fuse is selected based on the line voltage.
The AC asynchronous motor protects the melt current that is too small (recommended 2 to 2.5 times the rated current of the motor). If it is too small, after a phase fuse is blown, it is possible to cause the motor to operate, and the heat relay must be contained.
1. Selection of fuse type
The appropriate type of fuse is selected based on the size of the use environment, load nature, and short-circuit current. For example, for a smaller capacity, an RT series cylindrical cap type fuse can be selected; relative to the short-circuit current is quite large or a flammable gas, the RT series should be selected by the RT series with a filler sealing fuse; in the machine control In the circuit, multi-use RL series spiral fuses; when the semiconductor power element and the thyristor should be used, the RS or RLS series fast fuse should be selected.
2. Selection of fuse rated voltages and rated current
The rated voltage of the fuse must not be less than the rated voltage of the circuit; the rated current of the fuse must not be less than the rated current of the melt; the breaking capability of the fuse should be greater than the larger short circuit current in the circuit.
3. Selection of fuse rated current
(1) Short-circuit protection of the light such as the light and electrothermal heat, the load of the melt, and the rated current of the melt should be equal to or slightly larger than the loaded rated current.
(2) Short-circuit protection of a motor that does not often start and starts, the rated current of the melt should not be less than 1.5-2.5 times motor rated current.
(3) Short-circuit protection of a motor running frequently and continuously running, the rated current of the melt should not be less than 3-3.5 times the motor of the motor.
(4) The starting protection of multiple electric motors, the rated current of the melt should not be less than 1.5-2.5 times the rated current of the larger power motor, plus the remaining motor rated current sum.