Wiring Guidelines - nord NORDAC SK 200E Manual

2.4 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 limiting values of the EMC directives, the following
instructions should be complied with.
(1) Ensure that all equipment in the control cabinet is securely earthed using short earthing cables which
have large cross-sections and are connected to a common earthing point or earthing bar. It is
especially important that all control devices connected to the frequency inverters (e.g. an automation
device) are connected to the same earthing point as the inverter itself, using a short cable with large
cross-section. Flat conductors (e.g. metal clamps) are preferable, as they have a lower impedance at
high frequencies.
(2) The bonding cable of the motor controlled by the frequency inverter should be connected directly to the
earthing terminal of the associated frequency inverter. The presence of a central earthing bar in the
control cabinet and the grouping together of all bonding conductors to this bar normally ensures safe
operation. (See also Chapter 8.3/8.4 EMC)
(3) 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.
(4) 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.
(5) Ensure that the contactors and brake chokes 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 protectors 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.
(6) Use screened or armoured cable for the load connections (motor cable) and earth the
screening/armour at both ends. The earthing should be made directly to the electrically conducting
mounting plate of the control cabinet or the screening angle of the EMC Kit (Section 2.4) or the EMC
screw connector of the frequency inverter.
In addition, an EMC-compliant cabling must be ensured. (see also Section 8.3/8.4 EMC)
The safety regulations must be complied with under all circumstances when installing the
NOTE
BU 0200 GB
frequency inverter!
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 for high voltage insulations must not be used on cables which are connected to the
frequency inverter.
Subject to technical alterations
2 Mounting and Installation
29