In electrical engineering, IEC 60269 is a set of technical standards for low-voltage power fuses. The standard is in four volumes, which describe general requirements, fuses for industrial and commercial applications, fuses for residential applications, and fuses to protect semiconductor devices. The IEC standard unifies several national standards, thereby improving the interchangeability of fuses in international trade. All fuses of different technologies tested to meet IEC standards will have similar time-current characteristics, which simplifies design and maintenance. IEC 60269-1 – Low-voltage fuses – Part 1: General requirements IEC 60269-2 – Low-voltage fuses – Part 2: Supplementary requirements for fuses for use by authorized persons (fuses mainly for industrial application) – Examples of standardized systems of fuses A to I IEC 60269-3 – Low-voltage fuses – Part 3: Supplementary requirements for fuses for use by unskilled persons (fuses mainly for household and similar applications) – Examples of standardized systems of fuses A to F IEC 60269-4 – Low-voltage fuses – Part 4: Supplementary requirements for fuse-links for the protection of semiconductor devices IEC 60269-5 – Low-voltage fuses – Part 5: Guidance for the application of low-voltage fuses IEC 60269-6 – Low-voltage fuses – Part 6: Supplementary requirements for fuse-links for the protection of solar photovoltaic energy systems IEC 60269-7 – Low-voltage fuses – Part 7: Supplementary requirements for fuse-links for the protection of batteries and battery systems
In IEC standards, the replaceable element is called a fuse link and the assembly of fuse link and fuse holder is called a fuse. North American standards call the replaceable element only the fuse.
Application categories and time-current characteristics
IEC 60269 unifies the electrical characteristics of fuses that are dimensionally interchangeable with fuses built to earlier British, German, French or Italian standards. The standard identifies application categories which classify the time-current characteristic of each type of fuse. The application category is a two-digit code. The first letter is a if the fuse is for short-circuit protection only; an associated device must provide overload protection. The first letter is g if the fuse is intended to operate even with currents as low as those that cause it to blow in one hour. These are considered general-purpose fuses for protection of wires.
The second letter indicates the type of equipment or system to be protected: D – North American time-delay fuses for motor circuits, UL 248 fuses G – General purpose protection of wires and cables M – Motors N – Conductors sized to North American practice, UL 248 fuses PV – Solar photovoltaic arrays as per 60269-6 R, S – Rectifiers or semiconductors as per 60269-5 Tr – Transformers
Any fuses built to the IEC 60269 standard and carrying the same application category (for example, gG or aM) will have similar electrical characteristics, time-current characteristics, and power dissipation as any other, even if the fuses are made in the packages standardized to the earlier national standards. Fuses of the same application category can be substituted for each other provided the voltage rating of the circuit does not exceed the fuse rating.
The tests recommended on Fuses by IEC 60269 are: Temperature rise & power dissipation test Non-fusing & Fusing test Verification of rated current test Overload test Verification of Time Current Characteristics and Gates
D type fuses
D-type (Diazed, from German "Diametral abgestuftes zweiteiliges Edisongewinde" for "diametrically graded two-part Edison thread") fuse cartridges have a bottle-shaped ceramic body with metal end caps and are used with screw-in fuse holders. Introduced in 1909 by Siemens, they are available today in five different body sizes, with ratings from 2 A up to 200 A (see table), though only D II and D III fuses are commonly used. The designation of a size consists of the letter D and a Roman numeral. Higher-voltage types rated up to 750 V have increased clearance distances and are longer than lower-voltage-rated fuses. They are available with interrupting ratings up to 50kA RMS, and are intended for use as incoming main protection from an electrical supply utility.
D0-type (Neozed) fuses were introduced in 1967 and use the same concept, but have a smaller, cylindrical body. They are available in three different sizes with ratings from 2 A up to 100 A (see table).