What is IEC 60947?
IEC 60947 is the international series of standards for low-voltage switchgear and controlgear: individual devices such as circuit breakers, disconnectors, contactors, motor starters, push buttons and proximity switches for circuits up to 1000 V AC or 1500 V DC. The series consists of a general Part 1 and more than twenty product parts, each defining the requirements, ratings and tests for one type of device. In Europe the parts are adopted as EN IEC 60947 standards, published in the Netherlands as NEN-EN-IEC 60947.
In OT environments, IEC 60947 determines how the components in a control cabinet or MCC switch, protect and survive a short circuit. If you can read the ratings on the nameplate, you can select components that match both the load and the installation.
🧠 What is and is not covered by IEC 60947?
The series is maintained by IEC technical committee TC 121 (subcommittee 121A). IEC 60947-1 contains the general rules that apply to every part: definitions, characteristics, construction requirements and test methods. The current sixth edition dates from 2020, replaced the fifth edition of 2007 with its amendments of 2010 and 2014, and was published in Europe as EN IEC 60947-1:2021. New in that edition are, among other things, Annex X on co-ordination between short-circuit protective devices in the same circuit, improved DC testing, updated EMC tests and an example of a materials declaration (Annex W). The product parts always refer back to Part 1 and supplement it.
Just as important is what the series does not cover, because that is where misunderstandings arise in practice:
- Fuses - a fuse falls under IEC 60269. Only switch-fuse and fuse-combination units (load-break switches with fuses) fall under IEC 60947-3.
- Household miniature circuit breakers - domestic circuit breakers fall under IEC 60898-1, with the short-circuit rating Icn. Industrial MCBs are tested to IEC 60947-2, often alongside IEC 60898-1.
- Complete assemblies - the assembled switchboard falls under IEC 61439, and the electrical equipment of a machine under IEC 60204-1.
- General-purpose relays - an electromechanical relay for general use falls under IEC 61810. Contactor relays and auxiliary contacts of contactors do fall under IEC 60947-5-1.
🔧 Which parts make up the IEC 60947 series?
The table below lists the main parts with their current edition (as of 2026). IEC revises the parts independently, so always check the applicable version when you write a specification.
| Part | Subject | Edition |
|---|---|---|
| IEC 60947-1 | General rules for the whole series | 2020 |
| IEC 60947-2 | Circuit breakers (MCCB, ACB, industrial MCB) | 2024 |
| IEC 60947-3 | Switches, disconnectors, switch-disconnectors and fuse-combination units | 2020 + A1:2025 |
| IEC 60947-4-1 | Electromechanical contactors and motor starters | 2023 |
| IEC 60947-4-2 | Semiconductor motor controllers, such as the soft starter | 2020 + A1:2024 |
| IEC 60947-4-3 | Semiconductor controllers for non-motor loads | 2020 |
| IEC 60947-5-1 | Control circuit devices: push buttons, auxiliary contacts, position switches | 2024 |
| IEC 60947-5-2 | Inductive, capacitive and other proximity switches | 2019 |
| IEC 60947-5-3 | Proximity devices with defined behaviour under fault conditions (PDDB) | 2026 |
| IEC 60947-5-5 | Electrical emergency stop devices with mechanical latching | 2026 |
| IEC 60947-5-6 | NAMUR interface for proximity sensors | 1999 |
| IEC 60947-5-8 | Three-position enabling switches | 2020 |
| IEC 60947-6-1 | Automatic transfer switching equipment (ATSE) | 2026 |
| IEC 60947-6-2 | Control and protective switching devices (CPS) | 2020 |
| IEC 60947-7-1 | Terminal blocks for copper conductors | 2025 |
| IEC 60947-8 | Control units for built-in thermal motor protection (PTC) | 2021 |
| IEC 60947-9-1 | Active arc-fault mitigation (arc quenching devices) | 2019 |
There are also smaller parts, including the assessment of low-energy contacts (5-4), proximity devices with analogue output (5-7), flow rate switches (5-9), protective conductor and fuse terminal blocks (7-2 and 7-3), PCB terminal blocks (7-4) and optical arc detection (9-2). IEC also sells the complete series as a bundle; the 2026 version contains 26 documents.
⚡ Which ratings appear on the nameplate?
Part 1 and the product parts define a fixed set of characteristics. Manufacturers state them on the nameplate and in the datasheet, so you can compare brands on equal terms.
| Rating | Meaning | Example |
|---|---|---|
| Ue | Rated operational voltage | 400 V or 690 V AC |
| Ie | Rated operational current, always tied to a utilisation category | 32 A at AC-3, 400 V |
| Ui | Rated insulation voltage | 690 V or 1000 V |
| Uimp | Rated impulse withstand voltage | 6 kV or 8 kV |
| Icu | Rated ultimate short-circuit breaking capacity (circuit breaker) | 50 kA at 400 V |
| Ics | Rated service short-circuit breaking capacity, as a percentage of Icu | 25, 50, 75 or 100% of Icu |
| Icw | Rated short-time withstand current, with duration | 30 kA for 1 s |
| Icm | Rated short-circuit making capacity (peak value) | Depends on Icu and power factor |
In practice the difference between Icu and Ics matters most. After breaking a fault at Icu level, a circuit breaker only has to remain safe; after breaking at Ics level, it must be able to return to normal service. IEC 60947-2 also divides circuit breakers into selectivity category A (no intentional short-time delay on short circuit, typically MCCBs) and category B (a deliberate short-time delay with a declared Icw, typically air circuit breakers), so that the downstream breaker can clear the fault first.
🏭 What do utilisation categories such as AC-3 mean?
A contactor or switch does not have a single current rating, but a current per utilisation category. The category describes the load and therefore how demanding making and breaking will be.
| Category | Part | Typical load |
|---|---|---|
| AC-1 | 4-1 | Non-inductive or slightly inductive loads, such as resistance heating |
| AC-3 | 4-1 | Squirrel-cage motors: starting and switching off while running |
| AC-3e | 4-1 | High-efficiency motors with higher starting current (since 2018) |
| AC-4 | 4-1 | Squirrel-cage motors with plugging and inching |
| AC-15 / DC-13 | 5-1 | Coils and electromagnets in control circuits |
| AC-21 / AC-22 / AC-23 | 3 | Resistive, mixed and motor loads for disconnectors and switch-disconnectors |
| AC-53a / AC-53b | 4-2 | Soft starter without or with bypass |
The same contactor might switch 40 A at AC-1 but only 25 A at AC-3, because the starting current of an induction motor is six to eight times its rated current. At AC-4 the permitted current or number of operations drops further still. For a star-delta starter, you therefore select the contactors on the correct category, not on the largest figure in the catalogue. A variable frequency drive itself, incidentally, does not fall under IEC 60947 but under IEC 61800.
🛠️ How do you select components according to IEC 60947?
A practical sequence for a motor feeder or supply circuit in a machine or MCC:
- Determine the load and the utilisation category - motor (AC-3 or AC-3e), resistive load (AC-1) or control circuit (AC-15/DC-13), plus the number of operations per hour.
- Determine the prospective short-circuit current at that point - select a circuit breaker with an Icu above it and, where availability matters, an Ics at that level too.
- Choose the co-ordination type - under IEC 60947-4-1, a type 1 starter may be damaged after a short circuit; a type 2 starter can return to service without replacing parts, with at most lightly welded contacts. Use the combination tables tested by the manufacturer.
- Choose the trip class - with class 10, the thermal overload protection trips within 4 to 10 seconds at 7.2 times the set current; heavy starting requires class 20 or 30.
- Check selectivity - co-ordinate circuit breakers and motor protection using the manufacturer’s selectivity tables.
- Check the environment - pollution degree (usually 3 in industry), impulse voltage Uimp, ambient temperature and, in an Ex-zone, the additional requirements of IEC 60079 and ATEX.
Dutch and European context. The EN IEC 60947 parts are harmonised under the Low Voltage Directive 2014/35/EU (50–1000 V AC, 75–1500 V DC). A device that complies gains a presumption of conformity and carries the CE marking. The Machinery Regulation (EU) 2023/1230 replaces the Machinery Directive from 20 January 2027; for individual switching devices the Low Voltage Directive remains the framework. For the installation, NEN 1010 applies in the Netherlands, and NEN 3140 for safe working on it. In North America, derived standards such as UL 60947-4-1 exist, while circuit breakers there fall under UL 489.
🔐 What does IEC 60947 mean for safety and digitalisation?
For machine safety, IEC 60947 supplies the building blocks, not the assessment. An emergency stop button must open its contacts by direct opening action (IEC 60947-5-1 Annex K) and latch (IEC 60947-5-5). Whether the complete safety function with safety relays and contactors is reliable enough is assessed with ISO 13849-1 or IEC 62061. An ordinary sensor to 60947-5-2 is not a safety component; Part 5-3 exists for that purpose.
More and more devices are communicating: contactors and motor protection devices with IO-Link or a fieldbus module report current, temperature and operating cycles to the PLC. That enables condition-based maintenance, but IEC 60947 sets no cybersecurity requirements. For such devices and the networks they are connected to, you use IEC 62443 to support your compliance.
⚠️ Which mistakes are common in practice?
- Selecting a contactor on its AC-1 current for a motor load, or ignoring frequent starting (AC-4).
- No selective co-ordination between circuit breaker and motor protection, so a fault in one feeder trips the whole cabinet.
- Icu or Ics too low for the actual fault current, or confusing the Icn of a household breaker with the Icu of an industrial one.
- Not verifying the short-circuit withstand of the whole chain, including busbars, terminals and cables.
- Wrong sensor output - connecting a PNP or NPN sensor to an input card of the wrong type.
❓ Frequently asked questions
Does a fuse fall under IEC 60947?
No, a fuse falls under the IEC 60269 series. IEC 60947-3 only covers switches and switch-disconnectors that incorporate fuses, the so-called fuse-combination units. For the fuse itself, you refer to IEC 60269.
What is the difference between IEC 60947-2 and IEC 60898-1?
IEC 60947-2 is the product standard for industrial circuit breakers operated by skilled or instructed persons, rated with Icu and Ics. IEC 60898-1 applies to circuit breakers for household and similar installations, rated with Icn. The values of the two standards are not directly interchangeable.
What does AC-3 mean on a contactor?
AC-3 is the utilisation category from IEC 60947-4-1 for starting squirrel-cage motors and switching them off while running. The AC-3 current is the figure you use to select a contactor for a motor. For high-efficiency motors with a higher starting current, the category AC-3e has existed since 2018.
What is type 2 co-ordination?
Type 2 co-ordination under IEC 60947-4-1 means a motor starter can return to service after a short circuit without replacing any parts. Only lightly welded contacts are permitted. With type 1, the starter may be damaged and must be repaired.
Is IEC 60947 mandatory in the EU?
IEC 60947 as a standard is not legally mandatory, but its European versions are harmonised under the Low Voltage Directive. A manufacturer that designs its switchgear to EN IEC 60947 may presume that it meets the legal safety requirements. In the Netherlands, the parts are published as NEN-EN-IEC 60947.
What is the difference between IEC 60947 and IEC 61439?
IEC 60947 covers individual devices such as contactors and circuit breakers. IEC 61439 covers the complete low-voltage switchgear assembly in which those devices are installed, with requirements for temperature rise, short-circuit withstand and verification. An assembly to IEC 61439 is therefore filled with devices to IEC 60947.
📌 In summary
IEC 60947 is the product standard series for low-voltage switchgear and controlgear up to 1000 V AC and 1500 V DC, from circuit breaker and contactor to push button and proximity switch. With Part 1 as the common basis, ratings such as Icu, Ics and Ie, utilisation categories such as AC-3 and co-ordination types for motor starters, you can compare devices objectively and apply them safely in assemblies to IEC 61439 and machines to IEC 60204-1.