Fuses

We offer a wide range of fuse inserts in various designs: knife, tube, screw-on, and screw-in. We also provide accessories such as: fuse failure sensors, micro circuit breakers for fuse failure sensors, and fuse bases. For tube fuses, we also have bases that clip onto DIN rails.

What are fuses used for?

Fuses are used to protect electrical devices from the effects of short circuits and overloads. They contain fuse elements that burn out when an overload or short circuit occurs in the protected circuit. All fuses have a similar construction and consist of: a fuse element, a filler material, a housing, and contacts. The fuse element has appropriately shaped constrictions that define its time-current characteristics and is welded or soldered to the contacts of the fuse. The fuse element is surrounded by a filler material that extinguishes the electric arc. The filler material is usually special quartz sand. The entire assembly is placed in a ceramic housing called a body.

What are the basic parameters of fuses?

The basic parameters of fuses are:

• Rated current I_N [A] – the maximum effective value of the continuous current of the fuse under specified operating conditions. The rated current value is indicated on each fuse.
• Rated voltage U_N [V] – the maximum permissible value of the working voltage of the fuse.
• Joule integral I²t [A²s] – the minimum amount of energy required to blow the fuse.
• Breaking capacity [A] – the value of the expected short-circuit current that the fuse can interrupt at the rated voltage and under specified ambient temperature.
• Power dissipated [W] – the loss power dissipated in the fuse element when the rated current flows through it.
• Pre-arc time [s] – the time between the moment when the current through the fuse element is sufficient to cause the fuse to blow and the moment the arc forms.
• Arc time [s] – the time between the formation of the arc and the moment the fuse element melts.
• Interrupting time [s] – the sum of the pre-arc time and the arc time.

The time it takes for the fuse to blow depends on the value of the current, and the shorter the time, the higher the overload current. This time for a given current can be read from the fuse’s time-current characteristic. The time-current characteristic is a curve that represents the average interruption times depending on the expected short-circuit or overload current.

Fuses are classified based on their time-current characteristics:

• aR – ultra-quick fuses, not full-range, used for protecting semiconductor devices, protecting only against short circuits
• gR – ultra-quick full-range fuses used for protecting semiconductor power devices, protecting against both short circuits and overloads.
• gL/gG – full-range time-lag fuses used to protect electrical devices and cables
• aM – non-full-range fuses used for protecting electric motors.
• gTr – full-range fuses used for protecting transformers

Fuse applications:

• Protection of cables;
• Protection of electrical devices;
• Protection of transformers;
• Protection of electric motors;
• Protection of capacitors;
• Protection of semiconductor power devices: diodes, IGBT transistors, thyristors;
• Protection of electronic devices: soft starters, inverters, rectifiers;
• Protection of HV transformers, voltage transformers, and HV motors.

What are ultra-quick fuses and what types are there?

Ultra-quick fuses, also known as Ultra-Quick, are designed to protect diodes and resistors, i.e., semiconductor elements. Their name comes from their ability to quickly cut off the current flow when an overload or short circuit occurs. This ensures effective protection of semiconductor elements from damage.

These types of fuses are divided into two types – aR or gR. The first type protects only against short circuits. These are non-full-range fuses. They only operate in the event of a sudden current increase.

The second type is ultra-quick full-range fuses, which protect not only against short circuits but also against overloads. This means that when the current exceeds the limit, they burn out completely in a short time. As a result, the full-range ultra-quick fuses interrupt the circuit, preventing further power flow.

How do ultra-quick fuses differ from traditional fuses?

Ultra-quick fuses are characterized by an extremely fast response time when a short circuit or overload occurs. They can interrupt the circuit in as little as a few milliseconds. Traditional fuses, on the other hand, operate more slowly, with the fuse element gradually heating up.

The way full-range and non-full-range fuses operate also determines their different applications. They are mainly used in circuits where protection against damage caused by varying current parameters is a priority. Examples include soft-start systems or frequency converters. A key feature that distinguishes ultra-quick fuses is their low I²t values. This parameter contributes to the strong ability of these elements to limit short-circuit currents.

At DACPOL, we offer Ultra-Quick fuses in various sizes, both in full-range and non-full-range versions.