Wiring Guidelines - nord NORDAC SK 5xxE Series Manual

2.6 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 control 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.
(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 Section. 8.3/8.4 EMC)
(3) Where possible, screened 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 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.
(6) Use screened or armoured cable for the load connections (motor cable) and earth the screening/armour
at both ends. If possible, 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).
In addition, an EMC-compliant cabling must be ensured. (see also Section 8.3/8.4 EMC). If required, an
optional output choke can be supplied.
The safety regulations must be complied with under all circumstances when installing the
NOTE
BU 0500 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 equipment for high voltage insulations must not be used on cables that are connected to
the frequency inverter.
Subject to technical alterations
2 Assembly and installation
23