Fuse Characteristics and Classification 1 Characteristics of fuses The rated current of the melt is not equal to the rated current of the fuse. The rated current of the melt is selected according to the load current of the equipment to be protected. The rated current of the fuse should be greater than the rated current of the melt. .

2 fuse classification (1) spiral fuse RL:

When the melting tube is filled with quartz sand and the melt is buried in it, when the melt melts, the arc is sprayed on the quartz sand and its gap, and the temperature can be rapidly reduced and extinguished. In order to facilitate the monitoring, one end of the fuse is equipped with a color point, and different colors indicate different melt currents. When the melt is melted, the color point jumps out, indicating that the melt has been blown. The rated current of the spiral fuse is 5~200A, and it is mainly used for the branch circuit with large short-circuit current or the place with flammable gas.

(2) Packed Tubular Fuse RT:

Filled-tube fuses are a limited-current fuse. Consisting of quartz fused ceramic tubes, contacts and silver-plated copper gridded melts. Filler-type fuses are mounted on special bases, such as bases with barriers or fuses as bases for isolation tools, operated by manual mechanisms. The rated current of the filler pipe fuse is 50-1000A, and it is mainly used for circuits with large short-circuit current or places with flammable gas.

(3) Non-filled tube fuse RM:

The fuse tube of the non-filled tube fuse is made of fibrous material. The melt used is a variable section zinc alloy sheet. When the melt is melted, some fiber materials of the fiber fusion tube are decomposed due to heat, and high-pressure gas is generated, so that the arc quickly extinguishes. The non-filled tube fuse has the characteristics of simple structure, good protection performance and convenient use, and is generally used in combination with a knife switch to form a fuse knife switch.

(4) Packed Closed Tube Type Fast Fuse RS:

Filled closed tube type quick-acting fuses are quick-acting fuses consisting of a fuse tube, contact base, action indicator and melt. The melt is silver in narrow cross-section or net-like form, and the melt is used once and cannot be replaced by itself. Because of its fast action, it is generally used as a semiconductor rectifier component.

Fuse classification identification:

1) for homes and similar applications, type gG;

2) For industrial applications, type gG, gM or aM.

The first letter indicates the melting range:

* "g" indicates a full range of fuse capacity fuse;

* "a" indicates a fuse that is part of the range of melting capacity.

The second letter indicates the application category. This letter accurately describes the time current characteristics, the normal time and current.

For example:

* "gG" indicates a universal full range fuse capacity fuse;

* "gM" denotes a fuse for protecting the full range of the fuse capacity of the motor circuit;

* "aM" indicates a fuse that is used to protect a part of the motor circuit's fusing capacity.

In addition: there are many ways to classify fuses. For example, according to the use of personnel, industrial fuses for professional use, and fuses used by ordinary people at home; divided by the form of the shell, there are open, closed, semi-closed fuses; according to the filling material, There are filler material fuses and non-filling material fuses; according to the characteristics of the action, there are delay dynamic characteristics, fast-acting characteristics, fast and slow-motion characteristics, ultra-fast action fuses and other characteristics. Below we do not follow this, we divide the fuses into the following categories according to the characteristics of normal use. 1. Low voltage fuse 2 . High voltage fuse 3 . Automotive fuses.

The choice of the melt rated current is due to the fact that various electrical equipments have a certain overload capacity, allowing operation under certain conditions for a longer period of time; and when the load exceeds the allowable value, it is required to protect the melt for a certain period of time. There are some equipment starting current is very large, but the start-up time is very short, so the protection characteristics of these equipment are required to adapt to the needs of equipment operation, the fuse is not to be blown at the start of the motor, under the action of the short-circuit current and exceeding the allowable overload current When it can be reliably blown, it plays a protective role. The selection of the melt rated current is too large, and the load cannot be blown in time in the event of a short circuit or long-term overload; if the selection is too small, it may melt under normal load current and affect normal operation. To ensure the normal operation of the equipment, it must be reasonable according to the nature of the load. Select the melt rated current.

(1) The rated current of the lighting circuit ≥ the sum of the operating currents of all the lighting devices on the circuit to be protected.

(2) Motor:

1 single direct starting motor melt rated current = (1.5 ~ 2.5) × rated motor current.

More than 2 sets of direct starting motors total protection melt rated current = (1.5 ~ 2.5) × the sum of the motor current.

3 step-down starting motor melt rated current = (1.5 ~ 2) × rated motor current.

4 winding motor rated current = (1.2 ~ 1.5) × rated motor current.

(3) The rated current of the melt at the low voltage side of the distribution transformer is (1.0 to 1.5) × the rated current of the low voltage side of the transformer.

(4) The rated capacity of the parallel capacitor group is (1.43 to 1.55) × rated current of the capacitor bank.

(5) Electric welder melt rated current = (1.5 ~ 2.5) × load current.

(6) The electronic rectifying element melt rated current ≥ 1.57 × rated current of the rectifier element.