NORD Drivesystems BU0300 - Manual (Page 21)

2 Assembly and installation
BU 0300 EN Subject to technical alterations 21
2.5 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. Should limit values in excess of the EMC guidelines be required,
then the following guidelines may be useful.
(1) Ensure that all devices are securely earthed using short earthing cables that have large cross-sections
and which are connected to a common earthing point or earthing rail. 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 PE cable for the motor controlled via the frequency inverter should be connected directly to the
earthing connection linked to the enclosure together with the PE for the relevant frequency inverter
feeder. 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.
(3) Where possible, shielded cables should be used for control loops. Carefully terminate cable ends and
ensure that the wires do not run over longer sections unshielded.
(4) The shields of analogue setpoint cables should only be earthed on one side on the frequency inverter.
(5) 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.
(6) Ensure that the contactors in the cabinet are interference protected, either by RC circuits in the case of
DC contactors or by free-wheeling diodes for AC contactors, whereby 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.
(7) Use shielded or armoured cable for the load connections and earth the shielding/armour at both ends (if
the motor is not integrated). If possible, directly at the inverter PE.
(8) A noise suppression filter is always present in the standard device. If the frequency inverter is mounted
directly on the motor, then noise suppression grade Class B1 is achieved. If the frequency inverter is
mounted close to the motor (e.g. wall mounted), noise suppression grade Class A1 is achieved with a
motor cable length of up to 15m (shielded cable).
(9) Select the lowest possible pulse frequency. This reduces the intensity of the electromagnetic
interference generated 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.