NORD Drivesystems BU0700 - Manual (Page 16)

NORDAC SK 700E Operating Manual
16 Subject to technical alterations BU 0700 GB-1411
2.9 Wiring guidelines
The frequency inverter has been developed for use in an industrial environment. In this environment, high levels of
electromagnetic interference can influence the frequency inverter. In general, correct installation ensures safe and problem-free
operation. To meet the limit values of the EMC directives , the following instructions should be complied with.
(1) Ensure that all equipment in the cabinet is securely earthed using short earthing cables that have large cross-sections and
which are connected to a common earthing point or earthing bar. It is especially important that every control device
connected to the frequency inverters (e.g. an automation device) is connected, using a short cable with large cross-section,
to the same earthing point as the inverter itself. Flat conductors (e.g. metal clamps are preferable, as they have a lower
impedance at high frequencies.
The PE lead of the motor controlled by the frequency inverter must be connected as directly as possible to the earth
connection of the cooling element, together with the PE of the corresponding frequency inverter mains supply. The presence
of a central earthing bar in the control cabinet and the grouping together of all PE conductors to this bar normally ensures
safe operation. (See also Chapter 8.3/8.4 EMC guidelines)
(2) Where possible, shielded cables should be used for control loops. The shielding at the cable end should be carefully sealed
and it must be ensured that the wires are not laid over longer distances without shielding.
The shields of analog setpoint cables should only be earthed on one side on the frequency inverter.
(3) The control cables should be installed as far as possible from power cables, using separate cable ducts, etc. Where cables
cross, an angle of 90° should be ensured as far as possible.
(4) Ensure that the contactors in the cabinet are interference protected, either by RC circuits in the case of AC contactors or by
free-wheeling diodes for DC contactors, for which the interference traps must be positioned on the contactor coils.
Varistors for over-voltage limitation are also effective. This interference suppression is particularly important when the
contactors are controlled by the relay in the frequency inverter.
(5) Shielded or protected cables should be used for load connections and the shielding/protection should be earthed at both
ends, if possible directly to the frequency inverter PE/shield angle.
(6) If the drive is to be used in an area sensitive to electromagnetic interference, then the use of noise suppression filters is
recommended to limit the cable-dependent and radiated interference from the inverter. In this case, the filter must be
mounted as closely as possible to the frequency inverter and fully earthed.
It is also an advantage if the inverter is installed together with the line filter in an EMC-proof enclosure, with EMC-compliant
cabling. (See also Chapter 8.3/8.4 EMC)
(7) Select the lowest possible switching frequency. This will reduce the intensity of the electromagnetic interference produced by
the frequency inverter.
The safety regulations must be complied with under all circumstances when installing the
frequency inverter!
Note
The control cables, line cables and motor cables must be laid separately. In no case should they be laid in
the same protective pipes/installation ducts.
The test equipment for high voltage insulations must not be used on cables that are connected to the
frequency inverter.