Fuse Standards and their classification

IEC 60269: Low-Voltage Fuses – Overview & Applications

IEC 60269 standardizes low-voltage fuses (≤1000 V AC, ≤1500 V DC) for global use. It is divided into six parts:

Part	Title	Application
IEC 60269-1	General requirements	Defines construction, ratings, testing methods, and terminology
IEC 60269-2	Fuses mainly for industrial applications	Includes standardized systems A–I (industrial, commercial use)
IEC 60269-3	Fuses mainly for household/residential applications	Includes standardized systems A–F
IEC 60269-4	Supplementary requirements for semiconductor protection	Special fuses for diodes, thyristors, IGBTs
IEC 60269-5	Guidance for application of fuses	Selection, coordination, and application notes
IEC 60269-6	Supplementary requirements for PV fuses	Special fuses for solar photovoltaic systems

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Key Terminology

·         Fuse-link: The replaceable element (melting part).

·         Fuse: The complete assembly of fuse-link + fuse holder.

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Fuse Application Categories (Code System)

IEC 60269 uses a two-letter code to classify fuse characteristics:

1.      First Letter – Operating Range

o    g → General-purpose fuse (can clear overloads + short circuits down to currents that blow in 1 hour).

o    a → Short-circuit protection only (must be paired with overload protection).

2.      Second Letter – Application Type

Code	Application
G	General-purpose protection of wires & cables
M	Motors
D	Time-delay fuses for motors (North American)
N	Conductor protection per North American UL
PV	Photovoltaic arrays (per IEC 60269-6)
R, S	Rectifiers / Semiconductors (per IEC 60269-5)
Tr	Transformers

👉 Example:

·         gG → General-purpose full-range fuse for wires/cables (most common industrial type).

·         aM → Motor protection fuse (short-circuit only, needs overload relay).

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Interchangeability

·         Any fuses built to IEC 60269 and marked with the same category (e.g., gG, aM) will have similar electrical & time-current characteristics, regardless of manufacturer.

·         They are interchangeable as long as the voltage rating of the fuse ≥ circuit voltage.

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Tests Recommended by IEC 60269

IEC prescribes the following type and routine tests for fuses:

1.      Temperature Rise & Power Dissipation Test – Ensures safe thermal behavior at rated current.

2.      Non-Fusing & Fusing Test – Verifies that the fuse doesn’t blow below a defined threshold, and must blow above another.

3.      Verification of Rated Current Test – Confirms current-carrying capacity.

4.      Overload Test – Checks endurance under overload conditions.

5.      Verification of Time-Current Characteristics (TCC) & Gates – Confirms fuse curve (melting vs operating zones).

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✅ Summary
IEC 60269 provides a harmonized global system for low-voltage fuses, ensuring compatibility across manufacturers. The application category code (gG, aM, gM, gPV, etc.) is the key for engineers to select the right fuse for conductors, motors, semiconductors, transformers, or PV arrays.

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