Grundfos CRE Safety Instructions And Other Important Information page 10

7.8.1 Residual-current circuit breakers
WARNING
Electric shock
Death or serious personal injury
‐
This product can cause a DC current in
the protective-earth conductor. If a
residual current-operated protective
(RCD) or monitoring (RCM) device is
used for protection in case of direct or
indirect contact, only an RCD or RCM
of Type B is allowed on the supply side
of this product.
The residual-current circuit breaker must be marked.
Take into account the total leakage current of all the
electrical equipment in the installation.
This product may cause a direct current in the
protective-earth conductor.
Connection example for three-phase supply
The figure shows an example of a mains-connected
three-phase motor with a main switch, a backup fuse
and a residual-current circuit breaker, type B.
1
L1
L2
L3
PE
Pos. Description
1 Residual-current circuit breaker, type B
L1 Phase 1
L2 Phase 2
L3 Phase 3
PE Protective earth
7.8.2 Overvoltage and undervoltage protection
Overvoltage and undervoltage may occur in case of
unstable power supply or a faulty installation. The
product stops if the voltage falls outside the
permissible voltage range. The product restarts
automatically when the voltage is within the
permissible voltage range. The product requires no
additional protection relay.
10
The product is protected against transients
from the power supply according to EN
61800-3. In areas with high lightning
intensity, we recommend external lightning
protection.
Overvoltage category:
The product is approved for Overvoltage category III
rating.
7.8.3 Overload protection
The motor-current protection settings are fixed for
each motor variants. The settings ensure that the
motor is protected against overtemperature in all
operating states with regard to supply voltage and
shaft load, including a blocked shaft.
The motors are current controlled and will respond by
reducing the speed if the shaft load increases more
than 10 % of the nominal load.
If the shaft load forces the speed down to minimum
speed, the motor shuts down.
A sudden increase in the motor current caused by a
fault where the peak of the motor current is increased
60 % above nominal will cause the motor to shut
down within 0.5 ms.
The product requires no additional protection.
7.8.4 Overtemperature protection
The motor is thermally protected by a temperature
measurement in the drive. It can handle the lack of
airflow over the motor in case the fan cover is
blocked. It also means that the protection has a built-
in memory retention.
The time from start to shutdown due to
L1
overtemperature is therefore always longer when
L2
starting at a motor temperature close to the ambient
L3
temperature compared with restarting after a
shutdown due to overtemperature.
7.8.5 Protection against phase unbalance
Phase unbalance on the power supply must be
minimised. The three-phase motor must be
connected to a power supply with a quality
corresponding to IEC 60146-1-1, class C. This also
ensures long life of the components.
7.8.6 Short-circuit current
The product's electronic power output short-circuit
protection circuitry meets the requirements of IEC
60364-4-41:2005/AMD1:-, Clause 411.
Model K: Suitable for use on a circuit capable of
delivering not more than 5000 rms symmetrical
amperes, 480 V maximum when protected by gG
fuses. See the section on fuse sizes.