Emc-Correct Installation - Grundfos CUE Series Installation And Operating Instructions Manual

6.1.2 Protection against short circuit, fuses
CUE and the supply system must be protected against short
circuit.
Grundfos requires that the backup fuses mentioned in section
12.3.3 Cable cross-section to signal terminals
protection against short circuit.
CUE offers complete short-circuit protection in case of a short
circuit on the motor output.
6.1.3 Additional protection
WARNING
Electric shock
Death or serious personal injury
- The leakage current to protective earth exceeds
3.5 mA.
If CUE is connected to an electrical installation where an earth
leakage circuit breaker (ELCB/RCD) is used as additional
protection, the circuit breaker must be of a type marked with the
following symbols:
The circuit breaker is type B.
The total leakage current of all the electrical equipment in the
installation must be taken into account.
The leakage current of CUE in normal operation can be seen in
section 12.4 Electrical data.
During startup and in asymmetrical supply systems, the leakage
current can be higher than normal and may cause the ELCB/RCD
to trip.
6.1.4 Motor protection
The motor requires no external motor protection. CUE protects
the motor against thermal overloading and blocking.
6.1.5 Protection against overcurrent
CUE has an internal overcurrent protection for overload
protection on the motor output.
6.1.6 Protection against mains voltage transients
CUE is protected against mains voltage transients according to
EN 61800-3, second environment.

6.2 EMC-correct installation

The motor cable must be screened for CUE to meet
EMC requirements.
This section provides guidelines for good practice when installing
CUE. Follow these guidelines to meet EN 61800-3, first
environment.
• Use only motor and signal cables with a braided metal screen
in applications without output filter.
• There are no special requirements to supply cables, apart
from local requirements.
• Leave the screen as close to the connecting terminals as
possible. See fig. 7.
• Avoid terminating the screen by twisting the ends. See fig. 9.
Use cable clamps or EMC screwed cable entries instead.
• Connect the screen to frame at both ends for both motor and
signal cables. See fig. 10. If the controller has no cable
clamps, connect only the screen to the CUE cabinet. See fig.
11.
are used for
ELCB/RCD
• Avoid unscreened motor and signal cables in electrical
cabinets with frequency converters.
• Make the motor cable as short as possible in applications
without output filter to limit the noise level and minimise
leakage currents.
• Screws for frame connections must always be tightened
whether a cable is connected or not.
• Keep mains cables, motor cables and signal cables separated
in the installation if possible.
Other installation methods may give similar EMC results if the
above guidelines for good practice are followed.
Fig. 8 Example of stripped cable with screen
Fig. 9 Do not twist the screen ends
Controller
Fig. 10 Example of connection of a 3-conductor bus cable with
screen connected at both ends
Controller
Fig. 11 Example of connection of a 3-conductor bus cable with
screen connected to CUE (controller with no cable
clamps)
CUE
CUE
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