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Fuse Products

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A fuse is a type of over-current protective device that is designed to be a sacrificial element in an electrical power system. Fuses are designed to open circuits when excessive currents are present due to over-currents, and in this manner are designed to prevent further damage to the system that might result if the fuse were not present. Fuses are sacrificial in that they are generally good for one time use and are destroyed in the process of operating. The use of fuses in a circuit provides cheap insurance should there be an accidental or unintentional fault in the system wiring or components.

According to the fuse standard IEC 60269-1, a fuse is “a device that by fusing of one or more of its specially designed and proportioned components opens the circuit in which it is inserted by breaking the current when this exceeds a given value for a sufficient time. The fuse comprises all the parts that form the complete device”.

This means that by definition, the term ‘fuse’ is inclusive of all of the components that work to protect the circuit from over-currents. This consists of a fuse base or fuse mount, the fuse link and where applicable, replacement handles, the fuse carrier or covers.

In common language the term “fuse” is synonymous for fuse-link. ‘Fuse base’ and ‘fuse carrier’ may be referred to a ‘fuse holder’. A fuse carrier hinged to the fuse holder may form a ‘fuse switch’ using the fuse as moving contact.

Several fuse systems, showing different shapes, contact styles, technologies, etc. have historically developed in different countries. Their electrical performance and operating characteristics are however worldwide accepted and covered by the International Standard IEC 60269 “Low Voltage Fuses”.

Fuses have many unique performance characteristics, such as:

Optimum Component Protection 
Fuses reduce short circuit (fault) currents that flow to a low value by "current limitation". There is no need for complex short circuit calculations and no concerns about costly future upgrades due to system expansion with increased fault currents. Their compact size offers low cost over-current protection for the highest short circuit levels.

Safety 
Fuses do not produce gas, flames, arcs or other materials when clearing any value of over-current up to the highest level of short circuit. In addition, the speed of operation on high short circuit currents limits significantly the flash hazard at the fault location.

Reliability 
No moving parts to wear out or become contaminated by dust, oil or corrosion and no nuisance tripping. If a fault occurs, the fuse immediately operates in its predetermined manner or co-ordinates with other circuit components. The cause of the fault is then ascertained, corrected and a new fuse fitted. Fuse replacement ensures protection is restored to its original state of integrity. It should be stressed that the time taken for the replacement is very small in relation to the fault correction.

Simple co-ordination
Standardised fuse characteristics and a high degree of current limitation ensure that there is simple and effective co-ordination between fuses and with other devices. 

Choosing the right fuse for your application is vital. A fuse is a protective device so if it’s not selected with care, the level of protection that your circuit will experience may be compromised. When your machine/circuit was designed, the designer carefully considered the level of protection that was required, so getting it wrong may have serious consequences. Also, please refer to ‘What is an Utilisation Category?’ in this section.

Fuses serve two main purposes: 

1. To protect components and equipment from costly damage caused by over-currents.
2. To isolate sub-systems from the main system once a fault has occurred.

Fuses are rated by current, voltage, breaking capacity (interrupt capability) and whether they are designed to operate on AC or DC circuits. The current rating of a fuse is the current that it can carry for indefinite time periods without opening. The voltage rating relates to the ability of the fuse to function and extinguish internal arcs when it opens. The breaking capacity is how large a short-circuit or fault current the fuse can interrupt or stop safely without allowing a continuing arc and without damaging the fuse body or fuse holder.

Fuses shall be selected according to the following criteria. 

• Maximum operational voltage – shall be equal or greater than the system operating voltage. 
• Rated breaking capacity – shall be equal to or greater than the maximum fault current expected in the circuit downstream the fuse. 
• Rated current – shall be equal to or greater than the continuous operating current of the circuit protected by the fuse. 
• Breaking range – partial range or full range breaking capacity according to the type of protection required. 
• Utilisation category – select according to the nature of equipment to be protected.

An over-current is a situation where a circuit experiences a current that is higher than the normal operating current. This is either an overload or a short circuit (fault) current.

An overload current is an excessive current relative to the normal operating current, but one which is confined to the normal conductive paths of the circuit. Overloads are often between one and six times the normal current level. They are usually caused by harmless temporary surges in current that occur when motors are started up or transformers are energised. Such overloads (transients) are very brief in duration and any rise in temperature is trivial and has no harmful effects on the circuit components. 

Continuous overloads can result from defective motors, overloaded equipment or too many loads on the one circuit. Such sustained overloads are destructive and must be cut off by protective devices (fuses) before they damage the circuit.

Short circuit currents are also commonly known as ‘fault currents’ and occur when a circuit is given an opportunity to flow through a shorter than normal path. Whereas overload currents occur at rather modest levels, the short circuit or fault current can be many hundreds of times larger than the normal operating current. If not cut off quickly, the resulting damage and destruction can be very serious. Engineers need to know the potential fault current when designing circuits. This is the value of the highest possible current in the event of a short circuit.

The prospective short circuit current is the value of the current that would flow if there was no protection in the circuit in the event of a short circuit. The lower the power factor of the installation, the higher the peak value of this destructive current. This is also commonly referred to as the potential fault current.

The potential fault current is the value of the current that would flow if there was no protection in the circuit in the event of a short circuit. The lower the power factor of the installation, the higher the peak value of this destructive current. This is also commonly referred to as the prospective short circuit current.

Fuses are in most cases marked with all the essential information required to select a replacement fuse or to enable you to select fuses for most common applications. Additional information, such as performance characteristics can be supplied by the fuse manufacturer. Standard markings are as follows:

• Fuse standard, size and reference. This defines the operating performance and mechanical design of the fuse.
• Voltage rating. Fuses may be operated up to the maximum voltage stated in the rating. Voltage ratings may be colour coded to reduce the risk of incorrect installation.
• Current rating. This represents the value of the current that the fuse can carry continuously with out deterioration under specified conditions.
• Rated breaking capacity. This is the maximum value of prospective current that a fuse is capable of breaking under standard conditions. In other words, the maximum amount of current that a fuse can tolerate without losing its physical integrity (physically breaking apart). Industrial fuses according to IEC 60269-2 have a minimum breaking capacity of A.C. 50kA and D.C 25kA respectively.
• Breaking range and utilization category are indicated by letter codes. The first (lower case) letter indicates the breaking range, i.e. the range of prospective currents the fuse is able to break. The second (capital) letter indicates the utilization category, i.e. time-current characteristics for typical applications.
• Fuse manufacturer or trademark.
• Manufacturer’s product reference or part number, required for additional information on the fuse.

Additional markings may include:

• Rated frequency if other than 50 or 60 Hz. 
• Date of manufacture, useful to trace back product design changes.
• Certification mark, asserting product quality by an independent certification body. 
• Conformity mark, stating conformity to applicable national directives. 
• Recycling mark, identifying responsible recycling organization. 

Yes, very important! Each fuse is marked with a nominal current rating. The current rating of the fuse must be higher than the circuit’s normal operating current. As to how much greater, it depends on a number of factors, including what type of opening characteristic you desire. Please contact Fuseco for more specific advice.

Every fuse link has a specific ampere rating. In selecting the ampere rating of a fuse, consideration must be given to the type of load, circuit requirements and the intended protection performance. Naturally, the fuse current rating needs to be higher than the circuit normal operating current. As to the question of how much higher, there are a lot of factors that need to be considered before selection. For further advice on this topic, please contact Fuseco.

Yes, very important! The voltage rating of the selected fuse must be greater than or equal to the circuit voltage. Since fuses have such low resistance, the voltage rating becomes critical only when the fuse is trying to open. The fuse must be able to open quickly, extinguish the arc after the fuse element has melted and prevent the system open circuit voltage from re-striking across the open fuse element.

Fuse links are voltage sensitive devices and it is important to note that the satisfactory operation of a fuse link under fault conditions is dependent on the system voltage. Therefore they must not be installed in circuits with a voltage above their voltage rating. They can however be used satisfactorily in circuits at lower voltage levels. For example, you can use a 500V rated fuse in any circuit that has up to 500V.

In most cases, people contact Fuseco when they need to replace an existing fuse that has blown. In such cases, it is paramount that either the identical fuse or an exact equivalent is provided. Care must be taken to make sure that the fuse provided is of the same utilisation category and has the same electrical performance of the original. If you need assistance with this, I welcome you to contact us and we would be very happy to assist you. Also, we provide many types of cross-reference charts on this website, wall charts and various tools that can assist you to identify equivalent fuse types.

During normal conditions, the fuse must carry the load current of the circuit without blowing and opening the circuit. However, when an over-current occurs, the fuse must interrupt the over-current and withstand the voltage across the fuse after arcing. It is important that designers take account of temporary conditions such as surges & spikes during fuse selection. To properly select a fuse the following items must be considered:

• Available short circuit current
• Voltage rating (AC or DC) 
• Full load current 
• Characteristics of components to be protected 
• Any in-rush characteristics of the circuit (eg. Motor start-up) 
• The available space 
• The ambient conditions 
• Any standards requirements 
• Suitability to the proposed fuse holder (eg. Power loss)

All fuses are designed to open a circuit to protect other valuable components from over-currents. However, they are not all designed to do it in the same way! There are many different types of fuse performance options and selecting the correct performance for your application is vital. For this purpose, the IEC created ‘Utilisation Categories’ which describe the various operating classes of fuses. For example, fuses that are designed to protect sensitive semiconductor devices are designed to open very quickly and let through a minimum amount of energy during an over-current yet motor protection fuses are designed to withstand large in-rush currents in multiple start-up situations. Some fuses only protect against short circuits when others also protect against overloads. There are many differences. Choosing the wrong fuse could potentially cause serious damage by under-protecting or could cause excessive down time due to nuisance-blowing. Fuseco can assist you to make the right choice.

“Partial range”, or “back up” fuses, are designed to interrupt short circuit currents only. They are generally used to extend the breaking range of other protection devices (e.g. electronic controls or circuit-breakers). LV partial range fuses are also called “a fuse-links” and marked with the letter “a”.

“Full range” means that the fuse can break any current able to melt the fuse element up to the rated breaking capacity. Full range fuses can be used as stand alone protection devices because they can protect against short circuit (fault) currents and overloads. LV fuse-links having full range capacity are also called “g fuse-links” and marked with the letter “g”.

A “g” class fuse or full range breaking capacity fuse, also known as a general purpose fuse, is a LV current limiting fuse capable of breaking all currents that can cause melting of the fuse element up to its rated breaking capacity. They are used for protection against both short circuit faults and overloads.

An “a” class fuse or partial range breaking capacity fuse, also known as a ‘back up’ fuse, is a LV current limiting fuse capable of breaking under specified conditions all currents between the lowest current K²In indicated on its time current characteristics and its related breaking capacity. “a” class fuses are generally used to provide short circuit protection. Where protection is required against over currents less than K²In (small over currents, overloads), these fuses either need to be used in conjunction with another suitable switching device or “g” class fuses must be used instead.

The time-current characteristic is a curve giving the time, for example the pre-arcing time, as a function of the prospective current under stated conditions of the operation. The time-current curve is used to achieve co-ordination with the other fuses or devices in the same installation. The time/current characteristics or melting curves are represented by graphs showing the operating time of the fuse in relation to current. The presentation of the time/current characteristics are specified in the IEC Standards.

Current limiting fuses contain a granular filler, usually high purity quartz sand of a defined grain size and packaging density. The specific grain size distribution provides room to expand for the vapours and gases produced by the arc and offers a large surface for efficient cooling. The filler does melt under the influence of high arc temperatures, absorbing an enormous amount of energy and extinguishing the arc well before current zero. Fused quartz and metal form a non-conductive fulgurite body that prevents re-striking of the arc.

Most LV fuse elements are made of copper (Cu). Fuse elements of fast acting fuses and HV fuses are primarily made of silver (Ag). Silver plated copper is also commonly used. As a rule, fuse elements of time delay fuses contain low melting point materials, e.g. tin (Sn) or zinc (Zn) and alloys thereof. Formerly used alloys containing lead (Pb) and cadmium (Cd) have widely been eliminated.

After a fault in a three phase system, all three fuse-links of the faulted circuit shall be replaced unless it is definitely known that no over-current passed through a specific phase. In systems without grounded natural, only two fuses are needed to interrupt a three phase fault. The third fuse seems to be completely operational as it still exhibits a low impedance and an intact indicator or striker.

However most of the time, if a fuse experiences an over-current that causes other fuses in other phases to open, its own fuse element is usually damaged or partly interrupted and as a result, its current carrying capacity is very limited. Furthermore, if not replaced, it would most probably not perform within its published performance characteristics in the event of another over-current.

Re-using damaged partial range fuse-links may be specifically dangerous in HV installations as the fuse elements may melt at currents much below the minimum breaking current and cause disastrous damage to the installation. 

A fuse link is a thermal device and as such may require some de-rating when used at elevated ambient temperatures. Fuse links can carry rated current up to an ambient of 40°C. When the ambient temperature is higher than 40°C de-rating may be required (a simple rule is to de-rate by 0.5 % per degree centigrade). The voltage rating is not dependent upon ambient temperature.

Direct currents are very difficult to stop or interrupt when compared to alternating currents. Alternating current sources reverse the flow of current many times a second (in some locations 100 times a second on 50 Hz systems). Each time the current reverses, it goes to zero in magnitude. A zero current is very easy for a melting fuse to stop or interrupt—it is already stopped, and there is no force trying to sustain an arc across the fuse element.

DC currents, as the name implies, are currents that travel in one direction only. They do not reverse. Fuses bear the entire burden (with no help from the current) of acting to stop these currents. The internal elements of a fuse must react to an over-current condition (usually by melting) and as they react, they must do so with enough capability to interrupt the current from flowing while extinguishing any arc that might form. DC fuses are relatively sophisticated devices that have many different internal elements that must work together. The complexity of DC fuses sometimes results in a higher cost than AC fuses that may contain only a single element. There are fuses with equal AC and DC voltage ratings, but the DC interrupt rating is significantly less than the AC interrupt rating. 

Direct currents are very difficult to stop or interrupt when compared to alternating currents. Alternating current sources reverse the flow of current many times a second (in some locations 100 times a second on 50 Hz systems). Each time the current reverses, it goes to zero in magnitude. A zero current is very easy for a melting fuse to stop or interrupt—it is already stopped, and there is no force trying to sustain an arc across the fuse element. 

DC currents, as the name implies, are currents that travel in one direction only. They do not reverse. Fuses bear the entire burden (with no help from the current) of acting to stop these currents. The internal elements of a fuse must react to an over-current condition (usually by melting) and as they react, they must do so with enough capability to interrupt the current from flowing while extinguishing any arc that might form. DC fuses are relatively sophisticated devices that have many different internal elements that must work together. 

There are fuses with equal AC and DC voltage ratings but in most cases, the DC voltage rating is significantly less than the AC voltage rating. If a fuse only has an AC voltage rating, it most probably was not designed for DC applications and hence has never been tested within a DC environment. If you would like to ask if a specific AC rated fuse can be used in a DC environment, please call Fuseco. 

Yes, very important! A fuse must be able to open the circuit during a short circuit without losing physical integrity. In other words, it should be able to exist under a maximum fault level load without physically cracking or disintegrating. The breaking capacity of a fuse is the maximum available current, at the rated voltage that the device can safely open without physically rupturing. The breaking capacity of the fuse must be greater than the potential fault (short circuit) current of the circuit. The Breaking Capacity is also known as the ‘Interrupting Rating’. It is expressed in amps (A) but breaking capacity values are often large numbers. For example, a breaking capacity of 120,000A is usually expressed as 120kA.

HRC means high rupturing capacity. Also known as high breaking capacity (HBC) or interrupting capacity. Usually ceramic and measured in kA.

Yes, it’s an important consideration. The IEC standards are followed by many European and Asian countries while the UL standards are followed by North America. Both of these standards have different ways of defining and measuring their criteria so UL and IEC rated fuses are not interchangeable. If you are replacing fuses, it is a good idea to replace with a fuse that complies to the same standard as the original fuse. If you are sourcing fuses to be used in exported equipment, make sure that the fuses comply with the destination country’s required standards.

The I²t value of a fuse is a measure of the energy which is required to open the fuse element and to interrupt the current. It is determined by factors such as the design of the fuse element, the type of filler, etc. The I²t value is also a direct measure for the let-through energy which is exposed to the item being protected by the fuse in case of an over-current situation. It is a function of current squared and time, hence it is expressed in A²s (amps x amps x seconds).

Semiconductor fuses are fuses that have been specifically designed to protect semiconductor devices. They are often also referred to as solid state fuses, rectifier fuses or ultra-rapid fuses. Semiconductor devices are extremely sensitive to current fluctuations and require special protection. To perform this function, semiconductor fuses are able to open the circuit (blow) significantly quicker than other fuse types, and it is extremely important that they are replaced by direct equivalents when required. Semiconductor fuses belong to the utilisation categories aR, gR and gS. 

Semiconductor fuses are not selected like other fuse types. The main selection criteria for a semiconductor fuse is its I²t value…. even more important than its current rating! This is because semiconductor devices are extremely sensitive to current fluctuations and the maximum amount of let-through energy that they are exposed to during an over-current needs to be accurately controlled. This is super-important when selecting fuse protection for semiconductor devices.

If you are replacing an existing fuse, make sure that the new selected fuse has an I²t value that within ±10% of the original fuse’s I²t value. In this case, I²t values need to be compared at the same system voltage.

If you are selecting a semiconductor fuse for a new application, the I²t value of the selected fuse must be lower (or quicker) than the lowest I²t value of any of the components being protected. This ensures that the fuse opens before allowing any damaging let-through current to reach the components. In addition, refer to the question ‘Can I enclose a semiconductor fuse in a fuse holder?’ in this section. 

Semiconductor fuses run hotter than most fuses. In order to achieve a very accurate melting temperature, these fuses have been engineered with a high proportion of pure silver in their element and their body filling is high quality silica, which helps to draw heat away from the fuse element. Due to this fact, it is generally accepted that they should not be enclosed so as to ensure sufficient cooling of the fuses so they can operate as specified. Fuse cooling is very challenging if the fuse holder doesn’t allow sufficient airflow around the fuse.

The ‘power loss’ value of a fuse is a measure of the heat emanating from the fuse under full load. It is used to determine how quickly the fuse dissipates its heat. This is also known as the ‘heat loss’, ‘watts loss’ or ‘heat dissipation value’. Power loss is measured in Watts. If any fuse is to be used in a fully enclosed holder, then the power loss rating of the fuse holder used must be greater than that of the fuse to ensure that there is sufficient dissipation of the heat around the fuse. In other words, the fuse holder’s ability to tolerate heat must be higher than the heat the fuse produces. If this is not followed, the fuse holder may warp, melt or explode. Due to the fact that semiconductor fuses run much hotter than type gG or type aM fuses, extra care must be taken when choosing fuse holders for them. 

Please don’t! If you do, then in the event of an over-current, you run the risk of experiencing critical damage to the semiconductor devices in the circuit. In plain words, your expensive components will blow before your fuse does.

Circuit breakers have the advantage of being resettable and operationally cheaper and they have certainly taken over the downstream protective role where the potential fault currents are lower. So if you have a fuse in a downstream role, then in some cases, YES you can replace it with a circuit breaker. 

However, due to their unique qualities, fuses are still required upstream in the critical role. They are, in essence, the ‘gatekeepers’ of the protection system. They are actually the most important protective device in the system.

Fuses have three unique characteristics:

1. They are safe. Modern fuses have extremely high breaking capacities – can withstand very high fault currents without rupturing.
2. Properly applied, fuses prevent ‘blackouts’. Only the fuse nearest the fault opens without upstream fuses (feeders or mains) being affected. Fuses can provide selective co-ordination.
3. Fuses provide optimum component protection by keeping fault currents to a low value… They are said to be current limiting.

So if you have a fuse in a critical upstream role. Then NO you cannot replace it with a circuit breaker. 

No, but they can significantly reduce the hazard of a fire! 

When properly selected, fuses are able to reliably protect wires and equipment from overheating by overloads and short circuit faults. Consequently, fuses significantly reduce the hazard of electric fire. Fuses can however not prevent fire caused by local overheating of poor contacts or damaged conductors as may occur at normal load current. The same applies in case of high impedance arc faults or surface discharges carrying currents too low to melt the fuse.

When a current passes through a fuse, a small amount of energy is dissipated due to the fuse’s resistance. This can depend on the type of material used in the fuse’s element design, the quality of the filler, the amount of ceramic in the fuse body, etc. The amount of heat dissipated by a fuse is expressed in terms of ‘power dissipation’ also known as ‘watts loss’ and is measured in Watts. The maximum power dissipation for each type/rating is specified in the IEC Standards.

A fuse is a type of over-current protective device that is designed to be a sacrificial element in an electrical power system. Fuses are designed to open circuits when excessive over-currents are present and are designed to prevent further damage to the system that might result if the fuse were not present. The use of fuses in a circuit provides cheap insurance should there be an accidental or unintentional fault in the system wiring or components. Low voltage fuses are very common in electrical systems and they come in diverse styles, shapes and sizes. Low voltage fuses are defined as fuses with a voltage rating less than or equal to 1,500V.

Several fuse systems, showing different shapes, contact styles, technologies, etc. have historically developed in different countries. There are many thousands of different low voltage fuses that exist in the world, however most of them belong to one of the following groups:

1. Sub-miniature and SMD fuses 
2. Miniature fuses 
3. Cartridge fuses 
4. British Standard fuses 
5. DIN NH Blade fuses 
6. Automotive & DC fuses 
7. European Standard & Bottle Fuses 
8. American Standard fuses 
9. Medium Voltage fuses 

Sub-miniature fuses are designed to primarily protect circuits from over-currents that are in a printed circuit board (PCB) environment. They are physically small so that they do not take up a lot of valuable space on the PCB and they are available in either ‘through-hole’ technology or ‘Surface Mount Device’ (SMD) technology. Through-hole technology means that the fuse has leads that are soldered to the PCB or the fuse sits in a holder that is soldered on to a PCB. SMD means that the fuse is placed onto a PCB via special adhesive. SMD fuses are the smallest fuses in the world and they often use a conductive film as the element.

Miniature fuse are relatively small in physical size and extremely diverse in application. The most common sizes are the 5 x 20mm (M205) and the 6.3 x 32mm (3AG) fuses, which account for the greatest volume sales of this group. Originally designed for automotive applications, today they are used in electronics, instrumentation, audio, power supply protection and thousands of different applications. They are still the largest group of fuses sold in the world by volume.

Cartridge fuses are very popular around the world, making this group a diverse range of fuses & represented by almost every brand. The three most popular sizes for industrial applications are 10 x 38mm, 14 x 51mm and 22 x 58mm and a great range of DIN Rail mountable fuse holders are available for them. For Australian service fuse applications, the 22 x 58mm and 30 x 57mm are very popular and for multimeter applications, a large range of European & American midget fuses is available.

Industrial fuses made to BS88 standards are very popular in countries like England, Australia and South Africa. The industrial versions are characterised by either clip-in tags, offset tags or centre tags. To install them in their holders, the usual practice is to screw the fuse to the inside of the fuse holder wedge which then slides into the holder base. British standards (eg. BS1361) also cover service fuses and J-Type fuses.

A large range of semiconductor (ultra rapid) industrial fuses made to BS88 standards are available and are very popular in countries like England, Australia and South Africa. Semiconductor fuses are very fast acting fuses, designed to protect sensitive semiconductor components in a circuit (eg. diodes, thyristors, transistors, TRIACs, etc). The British Standard range caters for many applications and has a trigger indicator / micro-switch option.

The DIN NH Blade fuse is sometimes referred to as the ‘Eurofuse’ because of its popularity in Europe but in fact, this style of fuse is also very popular in Asia, India, the Middle East, Australia and Africa. It features two lugs attached to the fuse plates which act as a facility for a special ‘fuse-puller” tool, two solid tags commonly known as blades and a blown fuse indicator on its top plate. DIN NH fuses are popular due to their reliable performance, low price and blown fuse indicator function. The fact that blown fuses can be replaced quickly thus minimizing downtime is another advantage.

There are many varieties of European DIN Standard Ultra Rapid (Semiconductor) fuses that have been manufactured over the years. Some of them were ‘limited production run’ versions and some of them were ‘specials’ made by only one brand. The most commonly used styles are the DIN00-80, the Square Body style and the DIN blade style. They are known for their diverse range of performance options, their high breaking capacities and their compact sizes. These are considered among the world’s most advanced fuse designs.

American Standard fuses are used in electrical systems in the USA, Canada and South America. In Australia & NZ, they are predominantly sourced as replacement parts for imported American equipment. They are manufactured to UL and CSA standards and the industrial versions are classified according to the following classes: T, J, L, RK5 & RK1. American Standard semiconductor fuses are popular solutions in many applications as are the compact midget fuses used to protect multimeters and various lower current applications.

Photovoltaic, or ‘PV’ as it is also known, refers to the technology that converts light directly into electricity. Electrical systems that convert the sun’s energy into electricity are very reliable as long as they are protected properly. Any solar installation is vulnerable to fault currents or lightning strikes. Today, fuses and surge arrestors are the most effective ways of protecting the wiring and all the electrical equipment in a photovoltaic system. The unique and specific nature of this protection has resulted in the creation of a whole new category of fuse products, known as Photovoltaic (PV) fuses. PV fuses are rated at 1000VDC and comply to the utilisation category ‘gPV’.

‘D’ fuses, or ‘bottle fuses’ as they are commonly referred to are mainly used for domestic applications in Europe as well as some light industrial applications. They derive their name from their unique bottle shape and have a colour coded indicator system at one end cap. Although their use is in decline in Europe, they are commonly required in Australia as replacement parts for imported European equipment.

The world of automotive fuses is expansive and progressive. In years gone by, the glass 3AG fuse was widely used in automotive applications but that was eventually replaced with the 6AC and then the legendary ATO blade fuse which is still being used today. In recent years there has been a proliferation of new auto fuse designs and car designers have many options to choose from. DC fuses are used in forklift and electric lift truck applications but are now also considered to be convenient solutions for other DC circuits.

SIBA have created a range of fuses specifically for marine applications. The range consists of a 5x25mm cylindrical fuses, bottle shape fuses and ISOMET NH blade fuses along with specialist fuse holders and accessories. They conform to the demanding IEC60269-2-1, VDE0636 and are engineered to the highest quality possible. They are part of the NATO stock number program and frequently used in military applications.

SIBA have created a range of fuses specifically to meet the stringent demands of mining applications. These fuses are available in various forms including bottle shape, NH Blade shape and cylindrical shape and all conform to the IEC utilisation category gB. Designed for ‘sparkless’ operation, this fuse range is the ultimate fusing system available for hazardous area mining applications.

Medium voltage fuses are defined as fuses with a voltage rating greater than 1,500V and less than or equal to 36,000V (36kV). MV fuses are primarily used for the protection of transformers, motors, CT’s and VT’s. They are very common in electrical systems and they come in diverse styles, shapes and sizes. The most common styles in Australia & NZ are DIN style, British Standard Air and British Standard Oil type. MV fuses are available in three IEC performance categories: Back Up, General Purpose and Full Range.

The DIN design is the most popular style of MV fuse used in the world. Originally designed in Germany, DIN fuses became the default fuses used in electrical systems in Europe and now are a global reference. DIN fuses are characterized by a cylindrical body with 35mm long DIN end caps at either end. DIN fuses are available with the Back Up performance characteristic.

Fuseco is proud to offer the SIBA brand of medium voltage fuses. SIBA is a long established German fuse manufacturer that is widely considered to produce the highest quality MV fuses in the world. SIBA MV fuses have parallel connected pure silver fuse elements, ensuring narrow tolerances of the time/current characteristics. SIBA fuses also contain the SIBA temperature limiter mechanism that protects against inadmissible temperature rises, a unique feature that has become a ‘must have’ choice for many protection engineers. 

The DIN design is the most popular style of MV fuse used in the world. Originally designed in Germany, DIN fuses became the default fuses used in electrical systems in Europe and now are a global reference. DIN fuses are characterized by a cylindrical body with 35mm long DIN end caps at either end. DIN fuses are available with the General Purpose performance characteristic.

Fuseco is proud to offer the SIBA brand of medium voltage fuses. SIBA is a long established German fuse manufacturer that is widely considered to produce the highest quality MV fuses in the world. SIBA MV fuses have parallel connected pure silver fuse elements, ensuring narrow tolerances of the time/current characteristics. SIBA fuses also contain the SIBA temperature limiter mechanism that protects against inadmissible temperature rises, a unique feature that has become a ‘must have’ choice for many protection engineers. 

The DIN design is the most popular style of MV fuse used in the world. Originally designed in Germany, DIN fuses became the default fuses used in electrical systems in Europe and now are a global reference. DIN fuses are characterized by a cylindrical body with 35mm long DIN end caps at either end. DIN fuses are available with the Full Range performance characteristic.

Fuseco is proud to offer the SIBA brand of medium voltage fuses. SIBA is a long established German fuse manufacturer that is widely considered to produce the highest quality MV fuses in the world. SIBA MV fuses have parallel connected pure silver fuse elements, ensuring narrow tolerances of the time/current characteristics. SIBA fuses also contain the SIBA temperature limiter mechanism that protects against inadmissible temperature rises, a unique feature that has become a ‘must have’ choice for many protection engineers. 

British standard oil fuses are back up fuses used in oil filled switchgear. Theses fuses comply with IEC 60282-1, BS 269-1 and ESI 12-8. To successfully operate in an oil immersion environment, British Standard oil fuses are specially designed to be oil-tight under pressure and to possess the unique mechanical properties required for use in oil filled switchgear.

Fuseco is proud to offer the SIBA brand of medium voltage fuses. SIBA is a long established German fuse manufacturer that is widely considered to produce the highest quality MV fuses in the world. SIBA MV fuses have parallel connected pure silver fuse elements, ensuring narrow tolerances of the time/current characteristics. SIBA fuses also contain the SIBA temperature limiter mechanism that protects against inadmissible temperature rises, a unique feature that has become a ‘must have’ choice for many protection engineers. 

Motor protection fuses are specially designed for use in a motor circuit (according to IEC 60644) and are available in DIN standard and British Standard design, providing great choice and flexibility to designers of switchboard panels. These fuses provide high reliability against cyclic and peak current loads and incorporate age resistant technology needed to cope with high motor start-up currents. 

They also feature low power losses thus minimising temperature increases in narrow contactor enclosures and low minimum interrupting currents for operation of over-currents in the range 3 - 3.5 times rated current.

Fuseco is proud to offer the SIBA brand of medium voltage fuses. SIBA is a long established German fuse manufacturer that is widely considered to produce the highest quality MV fuses in the world. SIBA MV fuses have parallel connected pure silver fuse elements, ensuring narrow tolerances of the time/current characteristics. SIBA fuses also contain the SIBA temperature limiter mechanism that protects against inadmissible temperature rises, a unique feature that has become a ‘must have’ choice for many protection engineers. 

VT Protection fuses are characterised by relatively small value current ratings and are exclusively used for the protection of voltage transformers.  VT fuses are available with the back up performance characteristic.

Fuseco is proud to offer the SIBA brand of medium voltage fuses. SIBA is a long established German fuse manufacturer that is widely considered to produce the highest quality MV fuses in the world. SIBA MV fuses have parallel connected pure silver fuse elements, ensuring narrow tolerances of the time/current characteristics. SIBA fuses also contain the SIBA temperature limiter mechanism that protects against inadmissible temperature rises, a unique feature that has become a ‘must have’ choice for many protection engineers. 

There are a number of reasons to choose the SIBA brand for your medium voltage fuse requirements, including the following:

• SIBA high voltage fuses are the ONLY brand to have the integrated Temperature Limiter mechanism. This has been a revelation for companies such as Energex, ETSA, Integral Energy, Western Power, ACTEW and Ausgrid. 
• SIBA fuses are the only fuses that are made in Germany. 
• SIBA have been manufacturing fuses since 1946. Their experience is unsurpassed. 

Fuses are primarily designed to protect equipment from two dangerous electrical events. They are (1) Overloads, and (2) Short Circuits (also known as ‘faults’). In the case of an overload, the current rises above the normal operating current and if it stays there for a period of time, the fuse element melts and the fuse opens the circuit. In the case of a short circuit, the current rise is of such magnitude and speed that a fuse usually opens the circuit very quickly. All quality fuses will be triggered by such events and should open their respective circuit. This is the traditional & common application of the fuse.

However, certain circuits can experience another event which has proven to be extremely dangerous…..temperature rise.

With many high voltage fuse applications, the temperatures can be several 100°C and this can normally be absorbed by the fuse link and the switchgear. However, in some circumstances, the core temperature of the fuse can rise very slowly. Some of the causes of excessive temperature rise include:

• Fuse links switch a fault current below their minimum breaking current. 
• Faults between the windings in the transformer can cause a long lasting fault current. 
• The transformer is operated above its capacity limit. 
• The fuse rated current chosen for transformer protection is too small. 
• Poor contacting. 
• Fuse link current carrying capacity can be reduced due to transient influences damaging individual elements of the melting element system. 
• A lack of air convection or poor switchgear heat dissipation.
• Other factors causing a very slow rise in the circuit current over a long period of time.

This situation can be disastrous because the fuse element could slowly melt while not separating (arcing) to open the circuit. Molten metal can still conduct electricity so the fuse will remain conducting, but the element has melted and has warped from its original design, thus not able to operate as a heat sensitive circuit protection device. If the current continues to rise slowly, the equipment is unprotected by the fuse, possibly leading to a catastrophic situation. Alternatively, if the circuit does experience an over-current after the fuse element has melted, the performance of the fuse will be unpredictable and unreliable. Furthermore, on-going heat stress significantly stresses and ages switchgear equipment.

During testing to IEC420, SIBA thought that it would be highly advantageous to reduce the temperature during and after a current interruption to protect the switchgear. SIBA have done two things to deal with this potential situation.

(1) SIBA have developed a melting activator that has reduced the internal operating rupture temperature of the fuse from 960°C to a much cooler 230°C. Now, the opening of the switchgear is no longer caused by the arcing of the melting element but the striker pin mechanism is triggered by the Melting Activator which in turn acts on the 3 pole trip-free release of the switchgear.

(2) The development of the melting activator has allowed the use of a new type of temperature limiter device in the fuse to activate a striker pin, which in turn operates the relay that protects the asset. This temperature limiter mechanism is a technology that is unique to the SIBA brand and has rapidly become the first choice for electrical engineers around the world. The operating points of the temperature limiter are in a range where temperature rises last longer than 10 minutes.

Incidentally, some high voltage fuse manufacturers still use the old technology of a pyrotechnic device to operate the fuse striker. SIBA believe that a mechanical spring-loaded striker pin system is a far more reliable and effective system and the temperature limiter mechanism has been incorporated into this system.

The Temperature Limiter function, coupled with the fact that all SIBA fuses are manufactured to the highest standards in Germany means that SIBA high voltage fuses represent excellent value and peace of mind.