Automatic Fuses

Automatic Fuse: It is a circuit element that protects the installation and electrical devices connected to the installation against overcurrents and short circuits. Automatic fuses cut off the electric current by detecting this situation in case of overcurrent or short circuit in the electrical installation.

K Automat It is the name given to three-phase fuse. The working principle is the same as the fuse.

Automatic fuse types: There are different types of automatic fuses depending on how much and how long the overcurrent exceeds the nominal current. In the market, these terms are also called B curve, C curve etc.

Type B automatic fuse: It is generally used in home lighting, socket and control circuits. It is known as fast type fuse.

C type automatic fuse: It is used in inductive loads, protection of loads such as motors, transformers. It is known as slow type fuse.

D type automatic fuse: It is used for protection of motors, welding, tailstock machines, sodium vapour lamps, x-ray devices with high inrush current.

K type automatic fuse: It is used in the protection of applications affected by overcurrent, 24 VDC power supplies, electronic ballasts.

Z type automatic fuse: Used in the protection of sensitive electronic circuits, limit switch applications, sensor circuits.

Fuse Opening Curves: Fuses have different opening times depending on their type.

What is the difference between type B and type C fuses: Type C fuses are more delayed type automatic fuses than type B fuses. B types are used in socket and lighting circuits in buildings and C type fuses are used in motor circuits.

However, in building applications in Turkey, there is generally an installation method such as B type fuses are used in lighting feeds and C type fuses are used in socket circuits. The reason for this is that there will be an electrical device with an electric motor such as a washing machine to be connected to the socket, so type C fuses are used in all sockets.

Meaning of the Letters on the Fuse

If you see letters and numbers such as B25 and C20 on vending machines, it means that this fuse is 25 ampere B series and 20 ampere C series.

MCB: It is the initials of Miniature Circuit Breaker, which is the English name of automatic fuse.

C16: It is a 16 ampere C series fuse

230/400V: Rated voltages

6000: Short circuit breaking capacity

3: Energy limitation class

Automatic Insurance Selection

When selecting an automatic fuse, the following points can be taken into consideration. Rated current of the fuse, number of poles, short circuit breaking capacity, type, i.e. opening curve. In addition, if specifically requested in the specifications, values such as operating and storage temperatures, whether the fuses operate in DC, puncture voltages, impact resistance can also be taken into consideration. Fuses should not be selected at currents higher than the current of the load to be protected

Opening Curves

I1 : Thermal tripping current

I2 : Thermal tripping current

I3 : Magnetic tripping current

I4 : Magnetic opening current

Sudden Opening Conditions and the meanings of the letters B,C,D;

Type B fuses are generally used for the protection of lighting and socket circuits where inrush currents do not occur during switching, such as incandescent household lighting and electric heaters.

Type C fuses are generally used for the protection of circuits with inductive characteristics, transformers, air conditioners, refrigerators and a large number of fluorescent lamps where inrush currents occur during switching or switching on.

D type fuses are used for the protection of equipment such as motors, welding and spot welding machines, halogen and sodium vapour lamps and X-ray devices where very high inrush overcurrents occur at the moment of activation.

Basic Function of Automatic Fuses

Thermal protection is provided by bimetal inside the automaton (Overcurrent)

Magnetic protection is provided by the coil inside the vending machine in case of short circuit (Short Circuit)