History
First stage
The fuse was the first protection component used in electrical systems for more than 212 years, whose development can be divided into twelve stages for study. The history of fuses and the first stage of their development begins in the year 1674, at which time the results of the extensive research carried out by Rave were published. These experiments consisted of the study of the effect of electricity on plants, animals and human volunteers, for which high currents were produced by discharging capacitors (glass bottles covered internally and externally with metal plates), protecting the elements with a low section conductor. Subsequently, articles describing many experiments and explaining some extremely simple applications, such as the protection of telegraph systems, appeared in the 1880s.
It must be remembered that at that time only direct current was used, so in addition to fusion, the rapid separation of the electrodes had to occur in order to extinguish the electric arc. The first fuse designs were open type, so the conductive element, when it melted, was expelled in the form of drops, with more or less violence depending on the current energy that melted it. The risk of fire and personal injury was very high, so the fuse element began to be introduced into glass tubes with both ends open, reducing the aforementioned risks, without completely canceling them. This type of fuse could not cover the ends of the tube, since the result when it operated at high currents was its explosion.
In 1880, more precisely on May 4, Edison presented the first patent on fuses, with number 227226, which took place in the United States, which indicated that the fuse is the weak element of the circuit, since the presence of dangerous overcurrents for the circuit would cause it to melt and cut off the circulation of current. At that time, the main application was in the protection of expensive electric lamps, which were damaged by overcurrent and surges generated by the poverty of the voltage regulators used at that time. The first closed fuse was patented in England in 1890.
Following the first patents, countless designs can be found introducing extremely ingenious ideas, many of them in the direction of allowing the fuse to be reusable, that is, it should not be discarded after having operated.
Already at that time it was understood that one of the keys to the use of the fuse lay in its high reliability, an element that is seriously damaged by the necessary additions to allow the fuse to be reusable. From time to time, even today, new ideas arise to achieve this objective, but their applicability is low or non-existent, which is why the fuse element continues to be disposable or a single operation.
Second stage
It can be considered that the second stage begins in 1906, with the publication of the book by the German researcher Meyer, in which an analysis of the fusion process is presented, much more scientific than in previous articles. During this stage, the researchers dedicated their efforts mainly to predicting the relationship between the material and dimensions of the fuse element with the time it took for it to reach fusion. You begin to understand the thermal behavior of the fuse, axial and radial conduction, the effect of the terminals, etc. At that time, the main working parameter of the fuse for that time was defined, the minimum melting current. In that publication the so-called Meyer constant is presented, a value that allows the melting time of a fuse to be determined by the current density that passes through it and depending on the material used, under adiabatic conditions (without heat exchange). Analytically, Meyer's constant is the value of the integral of the current density squared, which stores in the element a sufficient amount of heat to cause fusion, an integral that was called specific energy.
The idea at that stage of development was that if the element reached fusion, it would eventually interrupt the overcurrent. It was soon recognized that meeting the first requirement did not always mean meeting the second. At that stage, the energies released by electrical systems in cases of failure began to exceed the capacity of the fuse to interrupt it, so fuse explosion began to be common. The low level of knowledge at the time about the interruption process did not allow us to recognize where the problem lay. It was normal to find in the instruction manuals on the handling of fuses, indications that today seem ridiculous, like that.
At this stage of development, electrical systems began to migrate from direct current to alternating current, so distribution lines of considerable length were built and the working voltage began to rise, already having systems with a few tens of kilovolts. At that level of development, open fuses were available, capable of operating from a few volts to 70 kV, called expulsion fuse, having very little current interruption capacity.
High-voltage devices were installed in solitary locations and at high points on the pole to reduce the risk of damage from ejected elements. This meant that fuses could only be used at these voltages for very low currents, being relegated to low-power and rural distribution systems.
For the protection and operation of these higher voltage systems, there were switches based on oil extinction, giving rise to the idea of using a combination of oil switch and fuse, called liquid or oil fuse. The fuse element, tensioned by a spring, is located inside the fuse is weakened by the temperature reached, the spring cuts it and moves it, lengthening the electric arc that goes out in oil. This device, in use for several years, allowed interruption powers much greater than expulsion powers.
The great variety of commercially available designs and the differences in design and application criteria led to the need for standardization, at which point work begins on specific standards in order to guarantee uniformity and interchangeability between manufacturers. Standards on fuses are approved in North America, Germany and England, which were the countries that led the development.
The idea of placing the fuse element immersed in filling material was explored, testing it with the following substances: chalk, marble, ground brick, sand, mica, carborudurm and asbestos, without reaching conclusive results.
Third stage
The third stage is considered to begin with the birth of the device called Power Fuse or fuse with filled outer material, which was introduced by German researchers during the 1940s. During that stage, extensive studies were carried out on the phenomenon of extinction of the electric arc and the influence of the filling, determining that the best extinguishing element was, and still is today, quartz sand. The idea of using quartz sand comes from its already widespread use for putting out fires.
Fourth stage
Next came the fourth stage called the dark age of the fuse, which was the period in which the Second World War broke out. At this stage, there was a rapid increase in the failure energies of the already important electrical systems, which in a very short time surpassed the pending developments to provide the fuse with the breaking capacity to handle them. Furthermore, at the same time the thermal magneto circuit breaker was introduced, which as a competitor seriously threatened the then overdue fuse. This situation continued until approximately 1945, that is, until the end of World War II, at which time new and ingenious fuse designs began to appear, with a significant variety in different types and applications.
Fifth stage
The introduction of important innovations to improve the performance of the fuse marked the beginning of the fifth stage. Such innovations are, fundamentally: the addition of the so-called effect, use of a fuse element with distributed section reductions, use of extinguishing material as filling, etc. These characteristics once again put the fuse in a position to compete with the newly arrived magneto-thermal switch, surpassing it in terms of breaking capacity and reliability. The high interrupting capacity fuse reached voltage levels of around 60 kV, thus entering the field in which until then it was almost exclusive to switches. From that moment until today, the fuse is the device with the highest volumetric capacity in the management of fault energy, which is achieved with rapid intervention, phenomena that are called limitation, which means that the fuse cancels the current without waiting for its natural passage through zero.
This period coincided with the great global expansion that followed the end of the war, growing the size and demand for electrical systems, giving rise to the birth of large fuse manufacturing companies, mainly in Europe and North America.
Sixth stage
The sixth stage originated with the introduction of the solid-state semiconductor, which took place in the early 1950s, although semiconductors with newly important powers saw the light during the 1970s. Power semiconductors have completely different operating characteristics than electrical systems. This difference is based, fundamentally, on its high energy density under nominal operating conditions and its reduced thermal capacity. In other words, power semiconductors handled high energy values in a very small volume, but had a very low capacity to withstand short-circuit type overcurrents. These characteristics required a new type of protective devices.
The fuse is far superior to other protective devices for this task, a function that still leads today. The adaptation of the traditional fuse to fulfill this new function was not quickly achieved, since initially the pre-existing fuse manufacturers were not able to develop the appropriate fuse. Faced with this difficulty, power semiconductor factories created their own divisions to develop specific fuses for their semiconductors. However, in a short space of time fuse manufacturers were able to understand the requirements of the semiconductor, harmonizing parameters and characteristics, taking charge of their manufacturing. The fuse factories belonging to the semiconductor manufacturers were slowly disappearing, as the experts once again took the business into their hands.
From that time until approximately the 1990s, the speed of fuse development slowed greatly, primarily due to the strong position of these devices in electrical systems. In that period, there was no exceptional innovation in the development of fuses, except the ability to perform much more precise analytical studies using the power of computers and analysis techniques such as finite element, finite difference, Transmission Line Network, etc. Such analytical studies allowed a better understanding of the operation and facilitated the optimization of the dimensions and materials used in the devices. Furthermore, we must not forget the extremely aggressive commercial policy and often with little technical foundation of the manufacturers of low-voltage thermo-magnetic switches, which are presented as the panacea of protection devices.
Seventh stage
In the 1990s, the seventh stage of fuse development began, which can be considered as generated by the so-called Slim Fuse. One of the most difficult fields of application of fuses is for low nominal currents, of the order from fractions of amperes to no more than 10 A. To operate properly with these nominal currents, the fuse element must have such small dimensions that they make it unmanageable in assembly, from a mechanical point of view. Thus appears the so-called Substrate Fuse, which consists of the conductive material deposited on an insulating plate, similar to the printed circuits widely developed for the assembly of electronic devices. Various techniques are used for deposition of the conductive material, such as photographic and acid attack used in printed circuits, vacuum deposition used in plating non-conductive materials, permeable mask applied in labeling, etc. Alumina, alicium"), mica, etc. are used as substrates. Currently, fuses of even smaller dimensions are being developed, called lithographic fuses, since they are obtained by the well-known offset method, using a very thin and flexible substrate. The need for small fuses is increasing, due to the miniaturization of electronics, and it can be stated that each modern electronic equipment currently has one or more fuses, such as mobile phones, digital cameras, camcorders, etc. Another field of very high current development is the automotive fuse, due to the increasing addition of electronics and electricity in the automobile. This, totally electric or simply hybrid, contains many electrical circuits and with them a large number of fuses, which would give rise to the next stage, is the addition of decision-making or adaptation capacity, which would cause its operation to be modified by working conditions regardless of the magnitude of the current. intelligent, of which some advances are already being produced, still incipient and highly protected due to their possibilities of being patented.