ElectricalEl. Equipment acc. EN IEC Machines

EN IEC 60204-1

A machine's electrical equipment shall

  • provide for safety of persons and property,
  • enable consistent control response, and
  • faciliate maintenance.

International standard IEC 60204-1 has been adopted as identical European Harmonized Standard EN 60204-1. It applies up to a supply voltage of 1000 V AC. These are its major requirements and recommendations:

Some types of machines have additional requirements, such as e.g.

  • Hoisting gear,
  • Semiconductor manufacturing equipment,
  • Mining equipment,
  • Machines for use in explosive atmoshere.

European standard EN 60335-1 with approx. 100 device-specific Parts 2 applies to household equipment.

Incoming Supply Connection

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A supply disconnecting device must be provded. Quite often this is a disconnector switch with or without fuses. Main disconnect must be lockable in its OFF-position e.g. by padlock, to avoid un-expected start-up of machine.

This main disconnect has been locked in its OFF-position on its housing, in order to avoid danger of electric shock during maintenance with open cabinet doors:

This main disconnect is appropriately marked.

This main disconnect his correctly labeled:

Main disconnect with labeling

Handle must be clearly marked. It must be positioned within easy reach at a height of 0,6…1,9 m above access level.

Excepted circuits, for e.g. cabinet illumination, may stay live when main disconnect is off, provided a warning sign is present.

Warning sign above a main disconnect switch

Protection of Equipment

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Machine and its electrical equipment must be protected against

  • Overcurrent arising from a short,
  • Overload of electrical motors,
  • Loss, reduction, or restitution, of supply voltage,
  • in cases even incorrect phase sequence and overvoltage,

among others.

Protection Against El. Shock

As generally in electrical installations, protection must be provided against

  • direct contact, mainly through insulation and enclosure, and
  • indirect contact (usually through grounding and automatic disconnection).

Sockets up to 20 A need ground fault/residual current interruptors. Label must warn against persisting residual voltage, e.g. of large capacitors.

Cabinets and boxes must be marked with the triangular lightening symbol W012 acc. EN ISO 7010. Cabinets may only be opened by tool or key, or after having been switched off.

Equipotential Bonding

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Protective bonding circuit is paramount for safety and reliability of electrical equipment. All exposed conductive parts shall be grounded, most importantly:

  • Metal ducts, metal cable trays and conduits;
  • Metallic cable armoring and sheaths; and
  • Pipes.

Connecting point for protective conductor must be clearly marked or labelled.

Operation incl. Emergency Stop

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All industrial machinery, except a few cases, must be capable of emergency stop to avert actual or impending danger. Emergency stop devices must be red.

Machines are operated by jog buttons with hold-to-run, two-hand control, or enabling switches. Special requiremnts are in force for wireless RF operation.

This emergency stop button is excecuted correctly, void of confusing inscription and symbols:

Correctly excecuted emgerncy stop mushroom button

All control circuits must be designed to fault to the safe side.

Operating a machine with open guards is subject to four conditions. Mode selector switch must be lockable in any position. Jogging is generally limited to safe reduced speed.

Collar as shown hinders quick operation with flat hand or fist. Prominent white arrows may be mistaken to indicate direction of actuation in emergency:

Emergency stop button with collar and prominent white arrows

Control Gear

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Enclosures prevent direct contact with live parts, and also protect devices from the environment. Pneumatic components such as directional valves should be mounted in separate enclosures.

All devices must be identifiable and easily accessible for maintenance.

Bonding braids to cabinet doors ensure good electromagnetic compatibility:

Grounding braid

Boxes containing pneumatic gear such as valves must have adequate venting. Otherwise even a small leakage may over time raise pressure and pose the risk of a physical explosion.

In order to isolate from all sources of engery, a manual valve for pressurized air supply must be clearly marked and freely accessible at all times:

Lockable main penuamtic cock

Conductors and Cables

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Conductors must be properly sized for all operating requirements (voltage, current, insulation) as well as ambient conditions (temperature, liquids, mechanical stress).

International standard EN IEC 60204-1 has minimum cross sections, as per ambient temperature, routing, and current carried.

Connections and Routing

All conductors to run from terminal to terminal without joints or splices. Different circuits may be bundled together, provided they have insulation for the highest voltage.

All conductors must be identifiable at their terminals according to the cricuit diagram provided.

These colors are standardized:

Circuit Color
Protective conductor Yellow/Green
Neutral conductor Blue
Excepted circuits Orange
Power circuits Black
AC control circuits Red
DC control circuits Blue

This cabinet is not grounded, furthermore grey phase has wrongly been attached to neutral terminal:

Severe mistake in electrical installation

Electric Motors

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A machine's electric motors must be protected against

  • Overcurrent,
  • Overtemperature, and
  • in cases, Overspeed.


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OEM have to conduct four mandatory tests only for verifcation of an industrial machine:

  • Compliance with documentation,
  • Continuity of equipotential bonding and grounding,
  • Automatic disconnection,
  • Functional tests.

Consultant for Electrical Engineering

I'd be glad to assist with all aspects of electrical safety. I offer to conduct acceptance inspections on your behalf, and perform those measurements mentionned above, among others. Do not hesitate to contact engineering consultant Wolfgang Grassberger, chartered engineer.


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Is a main disconnect mandatory for a machine?

Both European Machinery Directive 2006/42/EC and standard IEC 60204-1 for electrical equipement of machines mandate a supply disconnecting device. A plug with sufficient breaking capacity is permitted. In most cases though, a disconnecting switch is employed. This main disconnect must be lockable in its OFF-position, e.g. by padlock. Excepted circuits, such as for illumination, may stay live. Orange insulation must be used or warning sign attached..

Is an Emergency Stop mandatory for every machine?

As per European Machinery Directive 2006/42EC, each machine must have an emergency stop function, to avert actual or impending danger. There are but a few exceptions; hand-held machinery, or machines with large inertia, machines which cannot be stopped faster than normal, or where an emergency stop would impede necessary steps. A centrifugal casting machine is an example for this exception. It cannot quickly be stopped, and hot melted steel may then pour out.

Which is correct: Not-Halt or Not-Aus?

For quite some time, emergency stop has erroneously been translated into German as Not-Aus (emergency off), when dealing with dangerous movement. Current edition of international standard IEC 60204-1 explaines the difference: Emergency stop is intended to halt a process or movement, whereas emergency switching-off averts danger of electric shock. An example for the latter are slip-rings lacking other protection than separation.

Must electrical wires of a machine be numbered?

International standard IEC 60204-1 about electrical equipment of machines clearly states that each conductor must be identifiable according to the circuit diagram. Alphanumeric codes are the only viable alternative for wiring inside of the cabinet. Labeling is a substantial expense for the OEM, but saves a lot of machine downtime for the end user over the entire life.