Fuse sockets in electrical installations, together with fuse links, are used to provide protection against electric shock and to protect electrical installations and devices against the effects of short circuits and overloads.
The fuse sockets are designed for mounting fuse links . They are installed on mounting plates or standard TH35 rails. All ceramic fuse holders look similar, and they do not differ significantly in terms of construction - they have a ceramic housing (installation cover), metal fastening elements, a base and a cover. The fuse link is mounted directly in the socket using the so-called calibration insert and heads.
The fuse sockets differ in several parameters, but they must always be properly matched with the fuse links to fulfill their function of isolating the electric current . The safety of people, and secondly of devices and electrical installations, is a priority, which is why well-known and valued manufacturers of switchgear, such as Hager or ETI Polam always mark the sockets exactly fuse from their facilities.
D-type sockets, i.e. intended for households or similar applications, are manufactured in five physical sizes: DI, DII, DIII, DIV, DV. Of course, not every manufacturer offers a full range of socket sizes, just like all other components - only fuse links, heads or caliber inserts.
Sockets, as well as D fuse-links, are made for 500V, 690V, 750V and 1200V AC rated voltage and 250V, 440V, 600V DC. The rated current of the fuse link in the available range from 2 to 63 A, the number of poles and sometimes more precise data, such as, for example, total power losses for the rated current, are also determined for them. The fuse holders are made of ceramic.
Although the use of porcelain as an electric current insulation is not obvious to everyone, its thermal properties are already widely known. Ceramics has been used in the power industry almost since the birth of this field precisely because it has excellent insulating properties , and at the same time it is undemanding both in terms of the production process and materials.
Ceramic sockets are temperature-stable and do not conduct electricity. They are made of mixtures of raw materials based on alumina, zirconium or magnesium, as well as silicon carbide or cordierite ceramics. The exact recipe is a trade secret of the manufacturers, but due to the common knowledge and general availability of the ingredients, the strength, dielectric and thermal insulation parameters of products from different manufacturers are finally similar.
It is worth adding that nowadays fuse holders are also made of plastics
Fuse sockets are elements of switchgear, not only in electrical installations, but also in electronics. Due to lower voltages (although this is not a rule) and lower currents, electronic fuse sockets are not required to meet such high requirements in terms of insulating properties related to protection against the effects of electric shock or fire. Fuse sockets intended for use on PCBs, found in control circuits, mounted on a panel or rail, as well as for use on a wire or used in automotive circuits, are made of plastics. Most often equipped with tinned copper contacts and intended for soldering, they are usually designed for AC or DC voltage. Although they do not conduct high currents, they are exposed to high temperatures, therefore their strength and thermal insulation is also high, as is the case with power fuses.
