Em-Compatible Installation; Em-Compatible Enclosure Installation - Mitsubishi Electric FR-A800 Series Beginner's Manual

Connections
3.3

EM-compatible installation

Fast switching of electrical currents and voltages, which naturally also occurs when frequency invert-
ers are used, generates radio frequency interference (RF noise) that can be propagated both along ca-
bles and through the air. The power and signal cables of the inverter can act as noise transmission an-
tennas. Because of this the cabling work needs to be performed with the utmost care. The cables
connecting the inverter and the motor are a particularly powerful source of potential interference.
In the European Union several EMC (electromagnetic compatibility) directives have been passed with
regulations for the limitation of interference generated by variable-speed drive systems. To conform
to these regulations you must observe some basic guidelines when you are planning, installing and
wiring your systems:
● To reduce noise radiation install the equipment in a closed and properly earthed enclosure made
of metal.
● The inverter is equipped with a built-in EMC filter. Set the EMC filter valid. (For details, refer to the
Instruction Manual of your inverter).
● Ensure that everything is properly earthed.
● Install a motor and a control cable according to the EMC Installation Guidelines (BCN-A21041-204).
● Install sensitive equipment as far away as possible from interference sources or install the
interference sources in a separate enclosure.
● Keep signal and power cables separate. Avoid routing interference-suppressed cables (e.g. power
supply cables) and interference-prone cables (e.g. shielded motor cables) together for more than
short distances.
3.3.1

EM-compatible enclosure installation

The design of the enclosure is critical for compliance with the EMC directives. Please follow the fol-
lowing guidelines:
● Use an earthed enclosure made of metal.
● Use conductive seals between the cabinet door and chassis and connect the door and the chassis
with a thick, braided earth cable.
● If an EMC filter is installed make sure that it has a good electrically conductive connection to the
installation panel (remove paint etc). Ensure that the base on which the equipment is installed is
also properly connected to the switchgear cabinet earth.
● All cabinet plates should be welded or screwed together not more than 10cm apart to limit
transparency to RF noise. The diameters of any openings and cable glands in the cabinet should
not exceed 10cm and there should not be any unearthed components anywhere in the cabinet.
If larger openings are required they must be covered with wire mesh. Always remove paint etc.
between all metal-on-metal contacts to ensure good conductivity – for example between the
wire mesh covers and the cabinet.
● If inverters and controllers must be installed in the same cabinet they should be kept as far away
from one another as possible. It is better to use separate cabinets if possible. If you must install
everything in a single cabinet you can separate the inverters and controllers with a metal panel.
● Earth the installed equipment with short, thick earth conductors or suitable earthing strips.
Earthing strips with a large surface area are better for earthing RFI signals than equipotential
bonding conductors with large cross-sections.
Frequency Inverters - Beginner's Guide
EM-compatible installation
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