The IEC 60269 Family

IEC 60269 is the international standard for low-voltage fuses, covering applications up to 1000 V AC and 1500 V DC. It is structured into several parts, each addressing specific use cases:

• 60269-1: General requirements

• 60269-2: Fuses for industrial and commercial applications (replaceable by authorized personnel)

• 60269-3: Fuses for household and similar purposes (replaceable by non-professionals)

• 60269-4: Fuses for the protection of semiconductor devices

• 60269-5: Application guide for selection and coordination

• 60269-6: Fuses for photovoltaic systems

• 60269-7: Fuses for batteries and energy storage

China’s corresponding adoption is GB/T 13539, with Part 1 aligned to the general requirements. Though it became a recommended standard in 2017, it remains a primary reference for engineering design and equipment selection.

IEC 60269 usage categories

Usage Categories

Fuses are classified by letter codes that indicate their breaking range and application:

• Breaking range:

• g: Full-range breaking (overload and short-circuit)

• a: Partial-range breaking (short-circuit only; overload must be managed by relays or electronic protection)

• Application letters:

• G: General purpose (cables, conductors)

• M: Motor circuits

• R/S: Rectifiers and semiconductor devices

• PV: Photovoltaic systems

• Tr: Transformers (vendor-specific extensions such as gTr/gS for tailored matching)

Common Categories and Their Applications

• gG (General Purpose): Widely used for distribution feeders, branch circuits, and cable protection. Provides full-range protection with strong selectivity.

• aM (Motor Protection): Handles only short-circuit faults, allowing motor startup inrush currents to pass. Overload protection is provided separately by thermal relays.

• aR/gR (Semiconductor Protection): Ultra-fast acting, low let-through energy, designed for sensitive components like IGBTs, diodes, and rectifier bridges. Coordination depends heavily on I²t values.

• gPV (Photovoltaic Protection): Rated for 1000–1500 V DC, built to IEC 60269-6 requirements, including reverse current and low-fault-current behavior.

Standardized Fuse Forms

IEC defines several typical fuse designs:

• NH Blade-Type (Square with blades): High current capacity, common in industrial power distribution, requiring dedicated bases. Sizes include 000, 00, 0, 1, 2, 3, 4, and 4a.

• D/D0 (Diazed screw-type): Ceramic-bodied, bottle-shaped fuses traditionally used in European systems; D0 offers a compact variant for household use.

• Cylindrical fuses: Standard sizes such as 10×38 or 14×51 mm, often applied in PV arrays, control circuits, and power electronic front-ends.

• GB/T 13539.2 specifies corresponding structural dimensions for compliance in China.

Reading Fuse Designations

A complete fuse specification typically includes:

1. Usage category: gG, aM, gPV, aR, etc.

2. Rated voltage: e.g., 500 V AC, 690 V AC, 1000/1500 V DC

3. Rated current (In): e.g., 125 A

4. Size/series: e.g., NH1, 10×38, D02, BS88-2 gG

5. Breaking capacity: kA rating to withstand maximum prospective short-circuit current

6. I²t characteristics: For coordination with protected devices

Practical Examples

• Distribution feeder: gG 500 V, 125 A, NH1, 120 kA

• General-purpose, 500 V system, NH1 size, breaking capacity of 120 kA.

• Inverter input or PV string combiner: gPV 1000 V DC, 20 A, 10×38

• Photovoltaic full-range DC fuse, cylindrical 10×38 form factor.

This framework ensures proper fuse selection across industrial, commercial, residential, and renewable applications, safeguarding systems against both overloads and fault currents with precision and reliability.