By EECTECH | 16 July 2020 | 0 Comments
The role and model classification of low voltage fuses
Fuses are electrical appliances that use lighting circuits as overload and short circuit protection and as circuit protection in motor control circuits. It is connected in series in the line. When the line or electrical equipment is short-circuited or severely overloaded, the melt in the fuse first blows, so that the line or electrical equipment is disconnected from the power supply and plays a protective role. It is a protective electrical appliance. It has the advantages of simple structure, cheap price, convenient use and maintenance, small size and so on.
The most important part of a fuse is a fuse (or fuse), and the fuse is put into a box or an insulating tube to become a fuse. The specifications of the fuse are expressed by the rated current value of the fuse, but the rated current of the fuse is not the fusing current of the fuse, and the current of the fuse is generally 1.3 to 2.1 times greater than the rated current. The maximum current that a fuse can cut is called the current breaking capacity of the fuse. If the current is greater than this value, the arc cannot be extinguished during fusing, which may cause an explosion or other accidents.
Low-voltage fuse model classification The commonly used low-voltage fuses in the power supply system include porcelain plug-in type (RC), screw type (RL), closed tube type (RM), packed type (RTO) and self-resetting type (RZ). The following introduces several commonly used low-voltage fuses:
Porcelain plug-in fuse (RC1A): Porcelain plug-in fuse is composed of five parts: porcelain cover, porcelain low, moving contact, static contact and fuse. Both the porcelain cover and the porcelain low use the title of electrician porcelain. The power line and load line can be connected to the static contacts at both ends of the porcelain low respectively. There is a cavity in the middle of the porcelain low seat, which forms the arc extinguishing chamber with the protruding part of the lid. RC1A fuse is cheap and easy to replace. It is widely used in the circuit protection of lighting and small capacity motors.
Spiral fuse (RL): The spiral fuse is mainly composed of porcelain cap, fuse tube, porcelain sleeve, upper terminal, lower terminal and seat.
In addition to fuses, RL1 series spiral fuses are filled with quartz sand around the fuses for extinguishing the arc. There is a small red dot on the upper end of the fuse tube. The red dot will automatically fall off after the fuse is blown, indicating that the fuse has blown. When in use, insert the end of the fuse tube with red dots into the porcelain cap, the porcelain cap has threads, screw the nut together with the fuse tube into the porcelain low seat, and the fuse will connect the circuit.
During installation, the connection wire of the electrical equipment is connected to the upper terminal of the metal threaded shell, and the power cord is connected to the lower terminal of the base, so that when the fuse is replaced, the screw shell will not be charged.
Unfilled closed tube fuse (RM): Unfilled closed tube fuse, consisting of a fuse tube (ie fiber tube), two sockets and one or two fuses. The fuse of the fuse is a zinc sheet with one or several narrow cross-sections, which is installed in the fuse tube and contacts the socket through the cap of the fuse tube to form a current path. Its shape and structure are shown in the figure below: when the fuse is working normally, the wide part of the melt can conduct the heat generated by the narrow part, so it can withstand a large long-term working current. Under the short-circuit current, the narrow neck of the melt melts first. This is to artificially attract a weak link in the melt, and hope that this weak link will give full play to its role when short-circuiting, so as to improve its breaking capacity.
Filled closed tube fuse (RTO): Filled closed tube fuse is mainly composed of tube body, indicator, quartz sand filler and melt.
The tube body is made of talc ceramic, and the outer surface of the tube is made into a wave shape, which not only increases the surface heat dissipation area, but also is more beautiful. There are four screw holes at each end of the tube body, so that the cover plate can be installed with screws On the tube. The upper cover is equipped with a clear red indicator to indicate the fuse working condition. When the fuse is blown, the indicator is popped up. The melt is punched into a screen hole with a thin red copper sheet and surrounded by a cage shape. The middle is welded with pure tin. The two ends of the melt are spot welded to the metal plate to ensure good contact between the melt and the conductive insert. The tube is filled with specially treated quartz sand to cool and extinguish the arc.
Fast fuse: Since silicon semiconductor components are increasingly used in industrial power conversion and power drag devices, but the PN junction thermal capacity is low, the overload capacity of silicon semiconductor components is poor, and they can only withstand overload current in a very short time, otherwise the semiconductor components Burned out quickly. To this end, a fast fuse that can act quickly when overloaded must be used.
At present, the main series of fast fuse RLS, RSO and RS3. RLS series is a spiral fast fuse, it is used for short-circuit protection of small-capacity silicon rectifier s and some appropriate overload protection; RSO series is used for large-capacity silicon rectifier s, RS3 is used for short-circuit protection of thyristor s and some appropriate Overload protection.
EECTECH is a professional supplier of fuses. All have obtained CCC certification, complete fuse product specifications, high quality and low price. In addition to supplying standard products, we can also design and develop any special models and specifications of fuses according to customer needs.
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