AS ISO 14990.2 pdf download – Earth-moving machinery – Electrical safetyof machines utilizing electric drives andrelated components and systems Part 2: Particular requirements for externally-powered machines.
5.1.1 See Figure 2 (or an example of equipotential bonding for electrical equipment of an externally-powered EMM.
5.1.2 For EMM where the connection to the earthing system (machine bonding conductor) Is provided solely by flexible cables, the continuity of the protective conductor shall he ensured by appropriate design of the cable. Where there is a possibility that the cable and hence the machine bonding conductor could become damaged (e.g. a trailing cable dragged on the ground), the continuity of the protective bonding circuit shall be monitored. The supply to the electrical equipment of the machine or to the relevant part ot the machine shall be switched off whenever
— loss of continuity of the protective bonding circuit Is detected, or
— failure of the monitoring means occurs.
Exception: Maintenance operations involving devices such as battery chargers, block heaters and
similar devices, and GFCI/RCD protected circuits.
5.1.3 Each protective conductor connecting point on a machine shall be marked or labelled as such using the symbol IEC 60417.50191) or with the letters PE or by use of the bicolour combination GREEN.AND-YELLOW, or by any combination of these. The graphical symbol Is preferred
5.2 Guidance for type of neutral earthing system
For high-voltage equipment, the following general limitations for different voltage ranges and lengths of supply cable apply.
a) Direct earthing of the neutral
Only appropriate for system voltages less than 2 kV, (automatic disconnection of supply is always required).
b) Low impedance earthing of the neutral
May be appropriate for system voltages up to 36 kV and cable length up to 4 km (automatic disconnection of supply is normally necessary).
c) Isolated or high Impedance earthing of the neutral
Appropriate for system voltages up to 36 kV and cable length up to 8km, with the permissible cable length depending upon the capacitive reactance of all cables connected to the supply (automatic disconnection of supply is not normally necessary).
9.2 Supply conductors
Unless otherwise specified by the user, the supplier of the electrical equipment is not responsible for providing the overcurrent protective device for the supply conductors to the electrical equipment.
The supplier of the electrical equipment shall state on the installation diagram the data necessary for selecting the overcurrent protective device.
9.3 Socket outlets
Overcurrent protection shall be provided in the unearthed live conductors of each circuit feeding general-purpose socket outlets intended primarily for supplying power to maintenance equipment.
9.4 Protection against supply interruption or voltage reduction and subsequent restoration
Where a supply interruption or a voltage reduction can cause a hazardous situation, damage to the machine, or to the work in progress, undervoltage protection shall be provided by. for example, shutting down the machine at a predetermined voltage level.
Where the operation of the machine can allow for an interruption or a reduction of the voltage for a short time period, delayed undervoltage protection may be provided. The operation of the undervoltage device shall not impair the operation of any stopping control of the machine.
Upon restoration of the voltage or upon switching on the incoming supply, automatic or unexpected restarting of the machine shall be prevented where such a restart can cause a hazardous situation.
Where only a part of the machine or of the group of machines working together In a coordinated manner is affected by the voltage reduction or supply interruption, the undervoltage protection shall initiate appropriate control responses to ensure coordination.
9.5 Phase sequence protection
Where an incorrect phase sequence of the sLipply voltage can cause a hazardous situation or damage to the machine, protection shall be provided.
NOTE Conditions of use that can lead to an Incorrect phase sequence Include
— a machine transferred from one supply to another.
— a mobile machine with a facility for connection to an external power supply,
— supply cable repairs.
AS ISO 14990.2 pdf download – Earth-moving machinery – Electrical safetyof machines utilizing electric drives andrelated components and systems Part 2: Particular requirements for externally-powered machines
