Quick Answer: What Is IEC 60269?
IEC 60269 is the international standard family for low-voltage fuses. It defines requirements, test principles, utilization categories, physical fuse systems, and application rules for fuse links and fuse assemblies used in low-voltage electrical installations.
For engineers and panel builders, the most important practical points are:
| است | Short answer |
|---|---|
| What does IEC 60269 cover? | Low-voltage fuse links and fuse systems for industrial, domestic, semiconductor, photovoltaic, and other applications |
| Which part matters most for industrial panels? | IEC 60269-2, for fuses mainly used by authorized persons in industrial applications |
| What does gG mean? | Full-range general-purpose fuse, typically used for cable and feeder protection |
| What does aM mean? | Partial-range motor fuse for short-circuit protection; it must be used with separate overload protection |
| What are NH fuses? | Knife-blade industrial fuse links widely used in switchgear, distribution boards, and motor control centers |
| What should buyers check first? | Utilization category, rated voltage, rated current, breaking capacity, fuse size, holder compatibility, and time-current curve |
IEC 60269 Standard Parts at a Glance
IEC 60269 is a standard family, not one single product category. The exact part depends on the fuse application.
| IEC 60269 part | Main subject | ارتباط معمول |
|---|---|---|
| کمیسیون مستقل انتخابات ۶۰۲۶۹-۱ | General requirements for low-voltage fuses | Foundation for terminology, markings, performance, and test principles |
| کمیسیون مستقل انتخابات ۶۰۲۶۹-۲ | Supplementary requirements for fuses used by authorized persons, mainly industrial use | NH fuses, cylindrical industrial fuses, switchgear, control panels |
| کمیسیون مستقل انتخابات ۶۰۲۶۹-۳ | Supplementary requirements for fuses used by unskilled persons, mainly household and similar use | Domestic fuse systems and consumer-accessible applications |
| کمیسیون مستقل انتخابات ۶۰۲۶۹-۴ | Semiconductor fuse links | aR/gR protection for rectifiers, drives, power electronics |
| IEC 60269-5 | Guidance for application of low-voltage fuses | Selection and application guidance |
| IEC 60269-6 | Fuse links for photovoltaic systems | gPV fuses for solar PV strings and combiner boxes |
| IEC 60269-7 | Fuse links for batteries and battery systems | حفاظت از باتری و سیستمهای ذخیرهسازی انرژی |
For most VIOX industrial buyers, کمیسیون مستقل انتخابات ۶۰۲۶۹-۲ is the central part because it covers industrial low-voltage fuse systems such as NH and cylindrical fuse links. For solar combiner boxes, IEC 60269-6 becomes important because PV strings require DC-rated gPV fuse links.
IEC Fuse Terminology: Fuse Link, Fuse Holder, Fuse Base, Fuse Carrier
IEC terminology can be confusing because many buyers use “fuse” to mean different physical parts.
| اصطلاح | معنی | Procurement risk |
|---|---|---|
| لینک فیوز (Fuse link) | Replaceable current-interrupting element | Must match rating, category, voltage, breaking capacity, and size |
| Fuse holder | Device that holds and connects the fuse link | Must match fuse size, voltage, current, heat rise, and safety design |
| Fuse base | Fixed mounting base for the fuse link or carrier | Mechanical compatibility is critical |
| Fuse carrier | Removable carrier or drawer that holds the fuse link | Often confused with the fuse link itself |
| کلید فیوز جداکننده | Switching device incorporating fuse links | Must be evaluated for switching, isolation, and fuse compatibility |
For terminology differences, VIOX has a separate guide on fuse holder vs fuse block vs fuse carrier.
gG vs aM Fuse: The Most Important Selection Difference
The two-letter utilization category tells you what the fuse is designed to protect. In IEC fuse marking:
- The first letter describes the breaking range.
- The second letter describes the application.
| دسته بندی | Protection range | استفاده معمولی | Critical warning |
|---|---|---|---|
| gG | Full-range protection | Cables, feeders, general distribution | Protects against overload and short circuit |
| آ.م. | Partial-range protection | مدارهای موتور | Short-circuit protection only; needs overload relay |
| gPV | Full-range PV protection | Solar strings and combiner boxes | Must be DC and PV rated |
| آر | حفاظت نیمههادی با محدوده عملکرد جزئی | Rectifiers, thyristors, drives, power electronics | Very fast, but not general overload protection |
| gR | حفاظت نیمههادی با محدوده عملکرد کامل | Power semiconductor circuits | Requires careful I2t and curve coordination |
What Does gG Mean on a Fuse?
الف gG fuse is a full-range general-purpose fuse. It is commonly used for cable and feeder protection because it can operate in both overload and short-circuit conditions within its defined characteristic.
One detail often searched by engineers is the conventional fusing current of a gG fuse. For gG fuse links, the conventional fusing current is commonly associated with 1.6 x In under IEC time-current verification context. In practical terms, this is why gG fuses can protect cables against sustained overload, not only against heavy short circuits.
Do not use this one number alone to size a fuse. Final selection still depends on cable ampacity, installation method, ambient temperature, coordination, voltage rating, and manufacturer time-current data.
What Does aM Mean on a Fuse?
یک فیوز aM is a partial-range motor fuse. It is designed to tolerate motor starting current while interrupting high short-circuit current.
نکته کلیدی ساده است: aM fuses do not provide full overload protection by themselves. A motor circuit using aM fuses must include a properly selected overload relay, motor protection relay, or motor starter arrangement.
Can You Replace gG with aM?
Usually, no. Replacing a gG fuse with an aM fuse can remove overload protection from a cable or load circuit. In motor circuits, an aM fuse may be correct only when the rest of the motor protection system provides overload protection.
| Substitution | Usually safe? | دلیل |
|---|---|---|
| gG to aM | No, unless the circuit is redesigned | aM does not provide full overload protection |
| aM to gG | Sometimes electrically possible, but may cause nuisance operation | gG may operate during motor starting |
| Lower breaking capacity to higher breaking capacity | Often acceptable if all other ratings match | Higher breaking capacity can improve fault interruption margin |
| AC fuse to DC circuit | No unless the fuse is DC-rated for that voltage | DC arcs are harder to interrupt |
| Same size but different category | Not automatically | Physical fit does not mean protection equivalence |
gG Fuse Curve vs aM Fuse Curve
A fuse curve shows how quickly a fuse operates at different multiples of rated current. Engineers normally read this on a logarithmic time-current chart: current is shown horizontally, operating time is shown vertically, and the curve shape tells you whether the fuse can ride through starting current, clear a cable overload, or coordinate with upstream protection.
| Current condition | gG fuse behavior | aM fuse behavior |
|---|---|---|
| Mild overload | Designed to operate within its overload characteristic | Usually does not operate because overload protection is not its job |
| جریان راه اندازی موتور | May nuisance operate if selected incorrectly | Designed to tolerate motor inrush |
| جریان اتصال کوتاه بالا | Operates rapidly | Operates rapidly |
| حفاظت کابل | Suitable when properly selected | Not suitable as standalone cable overload protection |
| مدار انشعاب موتور | Possible, but inrush must be checked | Common when paired with overload relay |
For a motor circuit, the important visual difference is the overload region. A gG curve extends into the sustained overload area, while an aM curve is intentionally delayed or inactive through part of the motor-starting range. In practical coordination work, always compare the manufacturer’s actual time-current curve with the motor starting profile, overload relay setting, cable withstand limit, and upstream fuse or breaker curve.
How to Read the Curve
On most fuse time-current curves:
- The horizontal axis shows current, usually as amperes or multiples of rated current.
- The vertical axis shows operating time.
- The left side of the curve is slower overload behavior.
- The right side of the curve is short-circuit operation.
- aM curves deliberately avoid operation in parts of the overload region.
For a broader comparison with breaker behavior, see VIOX’s fuse vs MCB response time guide.
NH Fuse Sizes and Standard Fuse Sizes
NH fuses are industrial knife-blade fuse links commonly used in distribution boards, fuse switch disconnectors, motor control centers, transformer feeders, and high-current low-voltage panels.
The exact dimensions and ratings must be checked from the manufacturer datasheet and the matching fuse base. The table below is a practical selection reference, not a substitute for the product standard or datasheet.
| NH size | Typical current range direction | کاربرد متداول |
|---|---|---|
| NH000 / NH00C | Small industrial feeders and compact panels | Control panels, sub-distribution, small motors |
| NH00 | Up to the lower industrial range | Distribution boards, medium loads |
| NH0 | Smaller industrial use depending on system | Specialized panels and compact holders |
| NH1 | Medium industrial feeders | Motor control, distribution feeders |
| NH2 | Higher-current feeders | Larger motors, industrial circuits |
| NH3 | High-current distribution | Main distribution, transformer secondary circuits |
| NH4 | Very high-current service and distribution | Large industrial feeders and service entrance equipment |
For replacement work, do not use the NH size name alone. Ask for the manufacturer’s dimensional drawing and confirm the blade width, blade thickness, body length, contact centerline, indicator/striker position, and compatible fuse base or fuse switch disconnector. NH000, NH00C, and NH00 products can look similar in small-panel applications, but holder compatibility is not automatic.
| NH compatibility item | چرا مهم است |
|---|---|
| Blade width and thickness | Determines whether the knife contact seats correctly in the fuse base |
| Contact centerline and body length | Prevents poor alignment, partial insertion, or excessive contact heating |
| Fuse base or switch disconnector type | Confirms mechanical fit and safe operating clearance |
| Indicator or striker position | Must match the carrier, microswitch, or indication window if used |
| Power dissipation and enclosure temperature | Larger NH links can still overheat if the enclosure is compact or poorly ventilated |
NH Fuse Selection Checks
Before ordering an NH fuse link, confirm:
- NH size and fuse base compatibility
- utilization category, such as gG or aM
- جریان نامی
- rated voltage, AC or DC
- ظرفیت شکستن
- power dissipation and enclosure temperature
- striker or indicator requirement
- fuse switch disconnector compatibility
- whether live fuse replacement is prohibited by the site procedure
For high breaking capacity fuse construction, see VIOX’s HRC fuse guide.
Cylindrical IEC Fuse Sizes
Cylindrical fuse links are widely used in control circuits, compact panels, photovoltaic strings, semiconductor protection, and DIN rail fuse holders.
| Cylindrical size | استفاده معمولی |
|---|---|
| 10 x 38 mm | Control circuits, PV strings, compact protection |
| 14 x 51 mm | Industrial controls and power circuits |
| 22 x 58 mm | Higher-current control and distribution circuits |
Do not choose cylindrical fuses by dimension only. A 10 x 38 mm fuse may be used in different voltage classes and categories. A gG 10 x 38 fuse, a gPV 10 x 38 fuse, and a semiconductor fuse with similar dimensions are not interchangeable without rating verification.
gPV Fuses Under IEC 60269-6
Solar PV strings need fuses designed for photovoltaic DC fault conditions. That is the role of gPV fuse links under IEC 60269-6.
PV fuse selection is different from ordinary AC fuse selection because:
- PV strings operate on DC.
- DC current has no natural zero-crossing.
- parallel strings can backfeed fault current.
- string short-circuit current is close to operating current compared with many AC systems.
- voltage can rise under cold conditions.
For solar combiner boxes, gPV fuse selection should be coordinated with the PV module Isc, string count, maximum DC voltage, fuse holder voltage rating, and inverter/combiner box design.
For broader solar combiner box protection, see VIOX’s solar combiner box protection design guide.
IEC 60269 vs UL Class G Fuses
اصطلاح Class G fuse can create confusion because it sounds similar to IEC gG. IEC gG و UL Class G are not the same thing.
| اصطلاح | Standard family | معنی |
|---|---|---|
| gG fuse | IEC 60269 utilization category | General-purpose full-range fuse for cables and distribution |
| Class G fuse | UL 248 fuse class | North American dimensional and performance class |
| G in gG | Application letter in IEC code | General-purpose protection |
| Class G | UL fuse class name | Not equivalent to IEC gG marking |
If a buyer asks for “G fuse,” clarify whether they mean IEC gG, UL Class G, or simply a general-purpose fuse. This is especially important for export orders and replacement procurement.
How to Select an IEC 60269 Fuse
Use this sequence for practical fuse selection.
| قدم | What to decide | چرا مهم است |
|---|---|---|
| 1 | کاربرد | Cable, motor, PV, semiconductor, transformer, or battery system |
| 2 | دسته بندی استفاده | gG, aM, gPV, aR, gR, or other category |
| 3 | ولتاژ نامی | Must match AC or DC circuit voltage and system maximum |
| 4 | جریان نامی | Must coordinate with cable, load, and thermal environment |
| 5 | ظرفیت شکستن | Must exceed prospective short-circuit current at the installation point |
| 6 | اندازه فیزیکی | NH, cylindrical, D/D0, or other fuse system must match holder |
| 7 | منحنی زمان-جریان | Needed for selectivity and motor starting |
| 8 | I2t let-through | Important for semiconductor and current-limiting coordination |
| 9 | اتلاف توان | Affects enclosure heat and fuse holder temperature |
| 10 | مستندات | Datasheet, standard reference, marking, and test evidence |
For product evaluation, see the VIOX fuse product page.
اشتباهات رایج در انتخاب
Mistake 1: Selecting Only by Amp Rating
A “63A fuse” is not enough information. A 63A gG fuse, 63A aM fuse, and 63A gPV fuse can behave very differently.
Mistake 2: Treating Physical Fit as Electrical Compatibility
If a fuse link fits into a holder, it still may have the wrong category, voltage rating, breaking capacity, or time-current curve.
Mistake 3: Using aM as Standalone Motor Protection
aM fuses protect against short circuits, not sustained motor overload. Use them with a thermal overload relay or motor protection device.
Mistake 4: Ignoring DC Arc Interruption
AC-rated fuses should not be used in DC circuits unless the datasheet explicitly supports the DC voltage and application. PV and battery circuits require special attention.
Mistake 5: Confusing IEC gG with UL Class G
IEC gG is a utilization category. UL Class G is a North American fuse class. They are not interchangeable labels.
سوالات متداول
Which IEC 60269 part should I check for an industrial fuse panel?
For most industrial low-voltage panels, start with کمیسیون مستقل انتخابات ۶۰۲۶۹-۱ for general requirements and کمیسیون مستقل انتخابات ۶۰۲۶۹-۲ for industrial fuse systems used by authorized persons. If the panel includes solar PV strings, also check IEC 60269-6 for gPV fuse links. If the fuse protects semiconductor devices, drives, rectifiers, or power electronics, check کمیسیون مستقل انتخابات ۶۰۲۶۹-۴ and the manufacturer’s I2t data.
What is the practical difference between gG and aM when selecting a fuse?
استفاده کنید gG when the fuse must protect cables or feeders against both overload and short circuit. Use آ.م. only when the circuit has a separate overload protection device, such as a thermal overload relay or motor protection relay. The aM fuse is chosen to ride through motor starting current while still clearing high short-circuit current.
What do 1.25 x In and 1.6 x In mean for a gG fuse?
These values are part of the conventional non-fusing and fusing current concept used in IEC fuse verification. In practical terms, they help define how a gG fuse behaves under sustained overload conditions. They are not a complete sizing rule. Final selection still needs the cable ampacity, installation method, ambient temperature, enclosure heat rise, and the manufacturer’s time-current curve.
Why can aM fuses tolerate motor starting current?
aM fuses are partial-range motor fuses. Their time-current characteristic is designed so the fuse does not operate during normal motor starting, where current may be several times the rated motor current for a short time. This is why aM fuses must be coordinated with the motor’s starting profile and a separate overload device.
Can an aM fuse protect a cable by itself?
No. An aM fuse is not a standalone cable overload protection device. It is intended for short-circuit protection in motor circuits and must be paired with overload protection. If the circuit requires cable overload protection from the fuse itself, a properly selected gG fuse is usually the safer starting point.
Are NH000, NH00C, and NH00 fuses interchangeable?
Not automatically. These sizes can appear close in compact distribution panels, but the fuse holder or switch disconnector must match the fuse link. Before replacement, confirm the manufacturer’s drawing for blade width, blade thickness, body length, contact centerline, and the exact compatible base or carrier.
What should I check before replacing an NH fuse link with another brand?
Check the utilization category, rated voltage, rated current, breaking capacity, NH size, blade/contact dimensions, indicator or striker position, power dissipation, and holder compatibility. A replacement fuse should also meet the project approval requirements and should not increase enclosure heat beyond the holder or switch disconnector rating.
Why is the time-current curve more important than the amp rating alone?
Two fuses with the same amp rating can operate very differently. The curve determines motor-starting tolerance, overload clearing behavior, short-circuit response, and selectivity with upstream devices. For motor circuits, transformer feeders, semiconductor protection, and PV strings, the curve and I2t let-through energy are often more important than the printed current rating alone.
When should I use a gPV fuse instead of a gG fuse?
هرگز 5 سیم را مستقیماً وصل نکنید. آنها را به دو گروه 3 تایی تقسیم کنید، آنها را با یک سیم جامپر (pigtail) وصل کنید و آنها را به هم متصل کنید. gPV fuse when protecting photovoltaic DC strings or combiner box circuits. PV circuits have DC arcing behavior, high open-circuit voltage under cold conditions, and limited fault-current margin compared with many AC systems. A normal gG fuse should not be used in a PV DC string unless the datasheet explicitly supports that DC PV application.
Is IEC gG the same as UL Class G?
No. IEC gG is an IEC 60269 utilization category. UL Class G is a North American fuse class under the UL fuse system. The two names sound similar but refer to different standard frameworks.
Can IEC fuse links from different brands be substituted?
Sometimes, but only after datasheet verification. The replacement must match the IEC fuse system, utilization category, voltage rating, current rating, breaking capacity, physical size, holder compatibility, power dissipation limits, and any project-specific approval list. Brand substitution should never be based only on body size or label color.
How should I choose the breaking capacity of an IEC fuse?
The fuse breaking capacity must exceed the prospective short-circuit current at the installation point. For industrial panels, this value depends on transformer size, transformer impedance, cable length, upstream protection, and system voltage. Do not assume that a physically similar fuse has the same interrupting capability; verify the rated breaking capacity in the datasheet.
How do I know if an installed fuse has actually blown?
Some fuse links have indicators or striker pins, but not all indicators are visible in every holder. Visual inspection alone is not always enough, especially in enclosed panels or aged fuse carriers. For field testing methods, see VIOX’s guide on how to tell if a fuse is blown.
نتيجه گيری
IEC 60269 fuse selection is not just an ampere-rating exercise. A correct fuse specification must match the standard part, utilization category, voltage rating, current rating, breaking capacity, physical size, holder, and time-current curve.
Use this guide as the starting point for IEC fuse selection, then verify the exact datasheet curve, holder compatibility, enclosure temperature, and project standard before ordering or replacing a fuse link.
