• • • SAFETY IN ENGINEERING • • •
Machinery Electrical Safety
By Stewart Robinson MIET MInstMC, Advisory Consultant and Functional Safety Expert at TÜV SÜD, a global product testing and certification organisation
machinery. Electrical equipment of machines. General requirements. The standard applies to electrical, electronic and programmable electronic equipment and systems to machines not portable by hand while working, including a group of machines working together in a co- ordinated manner.
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The standard requires that electrical live parts be located inside enclosures or suitably insulated to provide protection against a human having direct contact with them. Any enclosures should only be able to be opened under one of three conditions:
1. A key or tool must be used to open it. 2. Before it can be opened, live parts must be automatically disconnected.
3. Opening without the use of a key or a tool and without disconnection of live parts shall only be possible when all live parts are protected against direct contact to at least IP2X or IPXXB (see standard IEC 60529).
Electrical operating areas (e.g. switchrooms), which allow a person to fully enter, must be provided with means to allow escape. The requirements for a ‘supply disconnecting device’ (an isolator) are also described in Clause 5 of EN 60204. An isolator must be provided for disconnection of each incoming supply and for each on-board power supply. The standard also allows for the operating means for a supply disconnecting device, that is not intended for emergency operations, to have a supplementary cover or door for protection against environmental conditions.
The terminal for the external protective conductor must be in the same compartment as the incoming supply not simply ‘in the vicinity.’ For the breaking capacity of the supply disconnecting device, the calculation must consider motors supplied by inverters or similar devices (power drive systems).
Supply disconnecting devices are also often provided for the purpose of isolating electrical equipment (Clause 5.5) instead of simply ‘devices for disconnecting…’ This is because while there has always been a distinction between ‘isolation’ and ‘disconnection’, it has not always been easily understood.
Measures for protection against electric shock are also described. This includes protection against direct contact (basic protection), and for
22 ELECTRICAL ENGINEERING • DECEMBER/JANUARY 2025
electricalengineeringmagazine.co.uk
he key standard for safety of electrical equipment of machines in Europe and the UK is BS EN 60204-1:2018 - Safety of
protection against indirect contact (fault protection). This is followed in the standard by measures for the protection of equipment. Equipotential bonding (earthing/grounding) is a basic provision for fault protection, so the standard also describes detailed requirements for protective conductors.
Clause 10 of the standard includes colour coding and marking requirements for actuators. Also, unless otherwise agreed between the machine supplier and the user (the details of which is covered in Annex B of EN 60204-1), machine status indicator lights should be colour coded, with each colour identifying a specific status.
Clause 17 of the standard outlines what technical documentation is required to demonstrate compliance. This includes information relating to a machine’s electrical installation, operation, and maintenance, which can be in the form of drawings, diagrams, charts, tables and instructions.
While verification can be done at different stages throughout the design and development lifecycle process, even at the end of it, it would be better to do this as early as possible during design. The extent of the verification that is required is
made clear in the specific product standard that relates to each different type of machine. However, where there is no such dedicated standard, EN 60204-1 requires that it must always include: • verification that the electrical equipment complies with its technical documentation • verification of continuity of the protective bonding circuit
• in case of protection against indirect contact by automatic disconnection, conditions for protection by automatic disconnection shall be verified according to 18.2 functional tests
EN 60204 often requires only a self-declaration against the conformance process. However, this does depend on the type of machine. For example, if EN 60204 was used for the presumption of conformity of an Annex IV machine, the electrical parts would still be included in the “special procedures” required.
The complexity of EN 60204, coupled with the potential lethal consequences if electrical safety is incorrectly administered, means that compliance is not a process that machine users can afford to get wrong. However, the development of a practical checklist is a useful approach that will help ensure all relevant considerations have been covered.
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