BOURNS MULTIFUSE resettable fuses. Reference data

Encyclopedia of radio electronics and electrical engineering / Reference materials

 Comments on the article

Designers of electronic devices know what fatal consequences for devices overcurrent can lead to. There are several ways to protect against such situations, the most common of them is the use of fuses. Of course, they work well, but they are designed for only one operation. When a fuse fails, it needs to be replaced, this is not always convenient, and in many cases the intervention of a qualified specialist is necessary.

The advantages of Bourns resettable fuses (SP) are: that they are designed for repeated operation, and their destruction occurs at a current many times greater than the operation current. Already today, joint ventures have found wide application in various areas of electronics and electrical engineering, such as personal computers, transformers, electric motors, sound-reproducing equipment, batteries, medical and measuring equipment, automotive electronics, etc. Like conventional fuses. The joint venture is connected to the power circuit in series with the load.

The joint venture is made of conductive plastic molded into a thin sheet by sputtering electrodes from both planes. Conductive plastic is a special substance, know-how of Bourns, consisting of a non-conductive crystalline polymer and the smallest particles of carbon black distributed in it, which conduct electric current. The electrodes guarantee a uniform distribution of energy over the entire surface area; wire or spade leads are attached to them.

A feature that allows this material to be used in SPs is that the conductive plastic exhibits a high non-linear positive temperature coefficient of resistance (PTC). Quite a lot of materials have a positive TCR, but the distinguishing feature of the SC material is the large steepness of the dependence of resistance on the temperature of the SC itself or the environment and an almost abrupt change in resistance from conductive to non-conductive (Fig. 1). Up to a certain, so-called "transitional" temperature, the resistance of the joint venture is almost constant, but when the "transitional" temperature is reached, the resistance increases sharply.

At room temperature, the SP material has a crystalline structure, the conductive particles of carbon black are located in it along the boundaries of the crystals very densely, close to each other, forming chains through which an electric current can pass (Fig. 2).

When an emergency occurs (for example, when the load is closed in the circuit where the SP is installed), current begins to flow through the SP. exceeding the nominal. The temperature of its material begins to increase until it reaches the so-called "phase transformation" temperature, at which the phase state of the polymer changes from crystalline to amorphous, accompanied by a slight expansion. The conductive particles of carbon black are not compressed by polymer crystals into dense chains, they move relative to each other and weakly conduct electric current. As a result, the resistance of the SP material increases sharply and it turns off (Fig. 3).

The SP remains in a "hot" state, providing constant protection, until the causes of its operation are eliminated. After the reasons for switching off are eliminated, the SP cools down, the polymer crystallizes again, the conductive chains are restored, and its resistance quickly returns to its original value. SP is ready to work again.

JV Multifuse is produced in several types of cases:

Disk with radial wire conclusions of the MF-R series. MF-RX (MF-R010-MF-R090. MF-R110-MF-R185 - fig. 4, a: MF-R090-0-9. MF-R250. MF-R300-MF-R900 - fig. 4,6, 250: MF-R0-10-4 - Fig. XNUMXc). These SPs are general purpose for through-hole or surface mounting.

Series MF-SM, MF-MSM - general purpose surface mount.

In flat rectangular cases with tape outputs of the MF-S series. MF-LS (Fig. 5) - to protect batteries from short circuits and overheating during charging

In frameless design - in the form of disks without leads.

Overall and mounting dimensions of the JV series MF-R are given in Table. 1, and the MF-S series - in table. 2.

In table. 3 shows the main electrical parameters of the joint venture.

Maximum operating voltage - the maximum allowable voltage that the joint venture can withstand without destruction at rated current.

Rated operating current - maximum current. which can carry out the joint venture without operation, i.e. without opening the load circuit.

Minimum actuation current - the minimum current through the joint venture. leading to a transition from a conductive state to a non-conductive state, i.e., to operation.

Initial resistance - resistance of the joint venture before the first operation (when received from the manufacturer).

In addition to those listed in Table. 3. The joint venture is characterized by one more parameter: the maximum allowable current - the maximum current that the joint venture can withstand without destruction. For the MF-B series JV it is 40 A. and for the MF-S series it is 100 A.

Since the joint venture is a device with a pronounced positive TCR. their characteristics depend on the ambient temperature. In table. 4 shows the dependences of the rated operating current and (through a fraction) the minimum operating current on the ambient temperature.

click to enlarge)

As you know, any heating takes some time. Because. that the joint ventures heat up, they do not switch instantly, but require some time, which depends not only on the ambient temperature, but also on the overload current flowing through them.

In table. 3 shows the operating time at a current approximately five times the rated operating current. The dependence of the SP operation time on the overload current is shown in fig. 6.

Bourns JVs are marked with the manufacturer's logo, series identifier, rated operating current code, and production date code (Fig. 7).

On the JV in frameless design in the form of disks, marking is not applied.

See other articles Section Reference materials.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Traffic noise delays the growth of chicks 06.05.2024

The sounds that surround us in modern cities are becoming increasingly piercing. However, few people think about how this noise affects the animal world, especially such delicate creatures as chicks that have not yet hatched from their eggs. Recent research is shedding light on this issue, indicating serious consequences for their development and survival. Scientists have found that exposure of zebra diamondback chicks to traffic noise can cause serious disruption to their development. Experiments have shown that noise pollution can significantly delay their hatching, and those chicks that do emerge face a number of health-promoting problems. The researchers also found that the negative effects of noise pollution extend into the adult birds. Reduced chances of reproduction and decreased fertility indicate the long-term effects that traffic noise has on wildlife. The study results highlight the need ... >>

Wireless speaker Samsung Music Frame HW-LS60D 06.05.2024

In the world of modern audio technology, manufacturers strive not only for impeccable sound quality, but also for combining functionality with aesthetics. One of the latest innovative steps in this direction is the new Samsung Music Frame HW-LS60D wireless speaker system, presented at the 2024 World of Samsung event. The Samsung HW-LS60D is more than just a speaker system, it's the art of frame-style sound. The combination of a 6-speaker system with Dolby Atmos support and a stylish photo frame design makes this product the perfect addition to any interior. The new Samsung Music Frame features advanced technologies including Adaptive Audio that delivers clear dialogue at any volume level, and automatic room optimization for rich audio reproduction. With support for Spotify, Tidal Hi-Fi and Bluetooth 5.2 connections, as well as smart assistant integration, this speaker is ready to satisfy your ... >>

A New Way to Control and Manipulate Optical Signals 05.05.2024

The modern world of science and technology is developing rapidly, and every day new methods and technologies appear that open up new prospects for us in various fields. One such innovation is the development by German scientists of a new way to control optical signals, which could lead to significant progress in the field of photonics. Recent research has allowed German scientists to create a tunable waveplate inside a fused silica waveguide. This method, based on the use of a liquid crystal layer, allows one to effectively change the polarization of light passing through a waveguide. This technological breakthrough opens up new prospects for the development of compact and efficient photonic devices capable of processing large volumes of data. The electro-optical control of polarization provided by the new method could provide the basis for a new class of integrated photonic devices. This opens up great opportunities for ... >>

Random news from the Archive Why does a toucan need a beak 21.02.2010 The toucans, living in the tropical forests of Central and South America, are known for their huge beaks. Various hypotheses have been put forward about its function. It can be used to squeeze the juice from fruit, to crack tough nuts, or to crush the shells of eggs stolen from other people's nests. It happens that birds fight with their powerful beaks. By loudly clicking its beak, the toucan can frighten and drive away enemies. In any case, this huge appendage of the head often complicates the life of its owner. Because of the beak, toucans are clumsy in flight. Some species, so that the beak does not interfere in sleep, even sleep on their backs, lifting it up. Canadian biologists have proven that the beak of a toucan also performs the function of thermoregulation. They placed the bird in an isolated chamber and gradually raised the temperature in it. When the temperature exceeded 25 degrees Celsius, the numerous blood vessels in the beak expanded and the heat began to be released into the air. Thus, the beak of a toucan (as, for example, the ears of an elephant) serves as a cooling radiator.

Other interesting news:

▪ Laser Air Defense System Light Shield

▪ Noise vs Noise

▪ Breaking the record for the length of a quantum communication line

▪ Carbon dioxide turned into coal

▪ A new source of green energy

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ site section Electrician's tool. Article selection

▪ article Am I my own ancestor? Popular expression

▪ article Which artist was the most prolific? Detailed answer

▪ article Tarragon. Legends, cultivation, methods of application

▪ article Capacitance meter of electrolytic capacitors. Encyclopedia of radio electronics and electrical engineering

▪ article Three experiments with coins. physical experiment

Leave your comment on this article:

All languages ​​of this page

Arabic	Hebrew	Polish
Bengali	Hindi	Portuguese
Chinese	Italian	Spanish
English	Japanese	Turkish
French	Korean	Ukrainian
German	Malay	Vietnamese

Home page | Library | Articles | Website map | Site Reviews

www.diagram.com.ua
2000-2024