1 the characteristics of the fuse
The melt is not equal to fuse rated current, rated current melt rated current according to the protected equipment choice, load current fuse rated current shall be greater than the rated current, melt determined in conjunction with the main electrical appliance.
2 fuse classification
(1) spiral fuse RL:
In fuse with quartz sand, melt buried among them, the melt fuse, electric arc spray to quartz sand and its aperture, can rapidly cool down and go out. To facilitate the monitoring, fuse end is equipped with color point, different colors represent different melt current, melt fuse, color points out, sign for the melt is fusing. Spiral fuse rated current for 5 ~ 200 a, it is mainly used for short circuit current large branch circuit or the places where flammable gases.
(2) there is packing fuse RT:
With filling tube fuse fuse is a limited flow effect. By the porcelain fused tube filled with quartz sand, contact and silver plated copper palisade melt. Filling tube fuse are packed in a special base, such as the base of breaker with isolation or fuse as the isolation knife, on the base of by manual operation. Filling tube fuse rated current is 50 ~ 1000 a, it is mainly used for short circuit current circuit or the places where flammable gas.
(3) no filler tube fuse RM:
No filler tube fuse fuse pipe is made from fiber content. Using melt for variable cross-section of zinc alloy. Melt blown fuse, fuse tube fiber part of the fiber material break down because of the heat, high pressure gas, make the arc soon go out. Packless tube fuse has simple structure and good protection performance, convenient use, etc, are usually combined with knife switch of fuse knife switch.
(4) packing seal tube type fast fuse RS:
Have packing sealing tube type quick fuse is a kind of quick action of fuse, the fuse, contact base, action of indicator and melt. The melt for silver narrow section or mesh form, melt for one-time use, unable to change. Due to its rapid action, generally for semiconductor rectifier cell protection.
The fuse classification identification:
1) used for residence and similar occasions, type gG.
2) used in industrial occasions, type gG, gM or aM.
The first letter indicates that fusing range:
* said "g" is the full range of fuse fusing capacity;
* said "a" is part of the scope of the fuse capacity of the fuse.
The second letter indicates that the application category, the letter shows correct time current characteristics, and conventional time and current.
For example:
* "gG" said gm's full range of fuse fusing capacity;
* "gM" is used to protect the full range of motor circuit fuse fusing capacity;
* said "aM" is used to protect the motor circuit part of the scope of fusing capacity of the fuse.
There are a lot of clock classification method also: fuse. By using personnel points, for example, has a professional staff use industrial fuse, fuse used by ordinary people and home; Points, the form of the shell are open, closed, semi-closed fuse; According to filling material, with and without filler material filler material fuse fuse; According to the feature points are, have delay dynamic characteristic, quick action, fast action, super fast movement characteristic fuse, etc. Here we are not in accordance with this, we according to the characteristics of the common when using the fuse is divided into the following several. 1) low voltage fuse (2) high voltage fuse 3. Automotive fuse.
The choice of the melt rated current
Because of various electrical equipment has certain overload ability, allow longer run under certain condition; And when the load exceeds allowable values, requires protection fuse melt in a certain period of time. And some equipment starting current is very big, but the starting time is short, so the protection requirements to the equipment features to meet the needs of the equipment operation, to fuse in motor starting without fusing, under the effect of short circuit current and exceed the permitted load current, reliable can fuse, protection. Melt choose larger rated current, load during short circuit or overload for a long time not fuse in time; Choice is too small, may be in the normal load current under the action of will fuse, affect the normal operation, in order to ensure the normal operation of equipment, must according to the nature of the load reasonably choose melt rated current.
(1) lighting circuit melt rated current protected circuit or the sum of all the lighting appliances working current.
(2) the motor:
(1) a single direct starting motor melt rated current = (1.5 ~ 2.5) x rated current of the motor.
(2) more directly starting motor protection always melt rated current = (1.5 ~ 2.5) by the sum of the electric motor current.
(3) step-down starting motor melt rated current = (1.5 ~ 2) x rated current of the motor.
(4) melt wound rotor motor rated current = (1.2 ~ 1.5) x rated current of the motor.
(3) the low voltage side of distribution transformer in the melt rated current = (1.0 ~ 1.5) x rated current on the low voltage side of transformer.
(4) parallel capacitor group melt rated current = (1.43 ~ 1.55) x rated current of capacitor set.
(5) welding melt rated current = (1.5 ~ 2.5) x the load current.
(6) electronic rectifier components melt rated current acuity 1.57 x rated current rectifier components.
